KR20220095306A - Apparatus for controlling braking for vehicle and contro method thereof - Google Patents

Abstract

According to one embodiment, a braking control device of a vehicle comprises: a brake lamp switch detecting operation of a brake pedal; a wheel speed sensor detecting speed of each wheel; and a control unit calculating wheel acceleration from wheel speed detected by the wheel speed sensor, low pass-filtering the calculated wheel acceleration through a low pass filter, calculating a wheel jerk amount from the wheel acceleration which is low pass-filtered, estimating a road surface friction coefficient of the wheel to be controlled by using a state of a brake switch, operation of ABS control of the wheel to be controlled, and the calculated wheel jerk amount, and estimating vehicle speed from the estimated road friction coefficient.

Description

Brake control device for vehicle and method for controlling the same

The disclosed invention relates to a braking control apparatus for a vehicle that performs braking control according to a road surface condition, and a control method therefor.

In general, a braking system that cannot utilize a pressure sensor that detects wheel pressure and a longitudinal acceleration sensor that detects the vehicle's longitudinal acceleration, particularly an antilock braking system (ABS), reduces the road friction coefficient in the first cycle of ABS control. It is very important to estimate. This is because, depending on how accurately the road friction coefficient can be estimated, the vehicle speed estimated based on the road friction coefficient varies, and the stability of the vehicle also varies according to the accuracy of the vehicle speed estimated during ABS control.

Conventionally, when ABS is operated on a low-friction road surface, if the pressure reduction by the inlet valve and the outlet valve is not properly performed, the accuracy of the estimated vehicle speed may be very low because the driving road surface is incorrectly judged as a high-friction road surface.

Accordingly, when the driver lightly presses the brake pedal on a low-friction road surface, the vehicle speed may be estimated to be lower than the actual speed, and thus proper ABS slip control may not be achieved, and thus the stability of the vehicle may be lowered.

Unexamined Patent Publication No. 10-1998-0035833 (published on Aug. 5, 1998) Laid-open Patent Publication No. 10-2011-0125130 (published on November 18, 2011)

SUMMARY One aspect of the disclosed invention is to provide a vehicle braking control apparatus capable of estimating a vehicle speed more accurately and reliably, and a method for controlling the same.

One aspect of the disclosed invention is a brake light switch for detecting the operation of a brake pedal; a wheel speed sensor for detecting the speed of each wheel; and calculating wheel acceleration from the wheel speed detected by the wheel speed sensor, low-pass filtering the calculated wheel acceleration through a low-pass filter, and calculating an amount of wheel jerk from the low-pass filtered wheel acceleration; A control unit for estimating the road friction coefficient of the control target wheel using the state of the brake light switch, whether the ABS control of the control target wheel is operating, and the calculated wheel jerk amount, and estimating the vehicle speed from the estimated road friction coefficient A vehicle braking control device may be provided.

When the brake light switch is on, the control target wheel is ABS, and the calculated wheel jerk is higher than a preset value, the control unit may control the road surface of the control target wheel based on the low-pass filtered wheel acceleration. The coefficient of friction can be estimated.

The controller may finally estimate the lowest road friction coefficient among the estimated road friction coefficient and the road friction coefficient of the other wheel as the road friction coefficient of the control target wheel.

When the brake light switch is turned off, the control target wheel is in ABS operation, or the calculated wheel jerk is lower than a preset value, the control unit sets the road friction coefficient of the control target wheel to a high friction road surface. It can be estimated by the coefficient of road friction.

Another aspect of the disclosed invention is to calculate wheel acceleration from the wheel speed detected by the wheel speed sensor, low-pass filter the calculated wheel acceleration through a low-pass filter, and calculate the amount of wheel jerk from the low-pass filtered wheel acceleration Calculating, estimating the road friction coefficient of the control target wheel using the state of the brake light switch, whether ABS control of the control target wheel is operating, and the calculated wheel jerk amount, and estimating the vehicle speed from the estimated road friction coefficient A method of controlling a brake control device for a vehicle may be provided.

Estimating the road friction coefficient is based on the low-pass filtered wheel acceleration when the brake light switch is on, the control target wheel is not in operation, and the calculated wheel jerk is higher than a preset value. The road friction coefficient of the control target wheel may be estimated.

In the estimating of the road friction coefficient, the lowest road friction coefficient among the estimated road friction coefficient and the road friction coefficients of other wheels may be finally estimated as the road friction coefficient of the control target wheel.

The estimating of the road friction coefficient includes determining the road friction coefficient of the control target wheel when the brake light switch is turned off, the control target wheel is in operation of ABS, or the calculated wheel jerk is lower than a preset value. It can be estimated by the road friction coefficient corresponding to the high friction road surface.

According to an aspect of the disclosed invention, it is possible to more accurately and reliably estimate a vehicle speed in the first cycle of ABS control, thereby improving vehicle stability.

1 illustrates a configuration of a vehicle to which a vehicle brake control apparatus according to an exemplary embodiment is applied.
2 illustrates a hydraulic circuit of a brake control apparatus for a vehicle according to an exemplary embodiment.
3 illustrates a control block of a brake control apparatus for a vehicle according to an exemplary embodiment.
4 illustrates an ABS control cycle in the brake control apparatus for a vehicle according to an exemplary embodiment.
5 is a diagram illustrating a method of controlling a brake control apparatus for a vehicle according to an exemplary embodiment.
6 is a diagram illustrating a control timing of a brake control apparatus for a vehicle according to an exemplary embodiment.

Like reference numerals refer to like elements throughout. This specification does not describe all elements of the embodiments, and general content in the technical field to which the disclosed invention pertains or content overlapping between the embodiments is omitted. The term 'part, module, member, block' used in this specification may be implemented in software or hardware, and according to embodiments, a plurality of 'part, module, member, block' may be implemented as one component, It is also possible for one 'part, module, member, block' to include a plurality of components.

Throughout the specification, when a part is “connected” with another part, it includes not only direct connection but also indirect connection, and indirect connection includes connection through a wireless communication network. do.

In addition, when a part "includes" a certain component, this means that other components may be further included, rather than excluding other components, unless otherwise stated.

Throughout the specification, when a member is said to be located “on” another member, this includes not only a case in which a member is in contact with another member but also a case in which another member exists between two members.

Terms such as 1st, 2nd, etc. are used to distinguish one component from another component, and the component is not limited by the above-mentioned terms. The singular expression includes the plural expression unless the context clearly dictates otherwise.

In each step, the identification code is used for convenience of description, and the identification code does not describe the order of each step, and each step may be performed differently from the specified order unless the specific order is clearly stated in the context. have.

1 illustrates a configuration of a vehicle to which a vehicle brake control apparatus according to an exemplary embodiment is applied.

1 , the vehicle includes a hydraulic pressure generating device 32 that generates brake hydraulic pressure based on the amount of operation the driver presses on a brake pedal 31, and each wheel FL, FR, It may include a hydraulic unit (HU) 33 for supplying braking force to RL and RR, and a control unit 34 for controlling the hydraulic unit 33 .

The control unit 34 may be referred to as an Electronic Control Unit (ECU).

The controller 34 may include a processor 34a and a memory 34b.

The memory 34b may store a program for processing or controlling the processor 34a and various data for operation of the vehicle brake control device.

The memory 34b includes not only volatile memories such as S-RAM and D-RAM, but also flash memory, read only memory (ROM), erasable programmable read only memory (EPROM), etc. of non-volatile memory.

The processor 34a may control the overall operation of the vehicle brake control device.

The brake light switch 35 is installed on the upper end of the brake pedal 31 so that when the brake pedal 31 is pressed, the contact is turned on to turn on the brake light, and when the brake pedal 31 is released, the contact is off to turn on the brake light. to turn off

The control unit 34 may recognize whether the brake pedal 31 is operated from a signal output from the brake light switch 35 .

The control unit 34 may receive each wheel speed information detected by each wheel speed sensor 36 .

The control unit 34 may adjust the brake hydraulic pressure supplied to or discharged from the brake calipers 41 provided on the respective wheels FL, RR, RL, and FR through the hydraulic unit HU 33 .

The hydraulic unit (HU) 33 may supply brake hydraulic pressure to the brake caliper 41 according to a control signal of the controller 34 .

The hydraulic unit (HU) 33 may discharge the brake hydraulic pressure of the brake caliper 41 according to a control signal of the controller 34 .

2 illustrates a hydraulic circuit of a brake control apparatus for a vehicle according to an exemplary embodiment.

Referring to FIG. 2 , the hydraulic pressure generating device 32 includes a booster VB for boosting the pedal effort of the brake pedal 31 and brake hydraulic pressure according to the pedal effort of the brake pedal 31 boosted by the booster VB. It may include a master cylinder (MC) for generating

Brake hydraulic pressure generated in the master cylinder MC may be supplied to the hydraulic unit 33 . The master cylinder MC may supply brake hydraulic pressure corresponding to a brake pedal operation amount by the driver to the hydraulic unit 33 .

The hydraulic unit 33 includes low-pressure accumulators LPA1 and LPA2 for temporarily storing brake fluid discharged from the wheel cylinders Wfr, Wrl, Wfl, and Wrr in each brake caliper 41, and the low-pressure accumulators LPA1 and LPA2. ), a hydraulic pump (HP1, HP2) that pumps the brake fluid stored in ) and supplies it to each wheel cylinder (Wfr, Wrl, Wfl, Wrr), a motor (M) connected to the hydraulic pump (HP1, HP2), and a master Solenoid valves (IN1-IN4) supplying brake fluid supplied from the cylinder (MC) or hydraulic pumps (HP1, HP2) to each wheel cylinder (Wfr, Wrl, Wfl, Wrr), and each wheel cylinder (Wfr, Wrl, Solenoid valves OUT1-OUT4 for discharging the brake fluid in Wfl and Wrr to the low-pressure accumulators LPA1 and LPA2 may be included.

The hydraulic unit 33 may include two hydraulic circuits HC1 and HC2 connected to the master cylinder MC.

The first hydraulic circuit HC1 and the second hydraulic circuit HC2 connect the brake hydraulic pressure generated by the master cylinder MC to each wheel cylinder Wfr, Wrl, Wfl, and Wrr. Each of the hydraulic circuits HC1 and HC2 may form a closed circuit in which the brake fluid circulates.

The first hydraulic circuit HC1 and the second hydraulic circuit HC2 may be controlled by connecting two wheel cylinders Wfr, Wrl, Wfl, and Wrr, respectively. The second hydraulic circuit HC2 is configured independently of the first hydraulic circuit HC1, but has the same arrangement structure.

A wheel cylinder Wfr providing a braking force to the right front wheel FR and a wheel cylinder Wrl providing a braking force to the left rear wheel RL are connected to the first hydraulic circuit HC1.

A wheel cylinder Wfl providing a braking force to the left front wheel FL and a wheel cylinder Wrr providing a braking force to the right rear wheel RR are connected to the second hydraulic circuit HC2 .

The normally open inlet valves IN1 and IN2 are provided on the inlet side of the wheel cylinders Wfr and Wrl in the first hydraulic circuit HC1, and the inlet side of the wheel cylinders Wfl and Wrr in the second hydraulic circuit HC2. The normally open inlet valves (IN3, IN4) are connected to the The normally open inlet valves IN1, IN2, IN3, and IN4 may be driven when the brake fluid pressure in each wheel cylinder Wfr, Wrl, Wfl, and Wrr is increased.

In addition, normally closed outlet valves OUT1 and OUT2 are connected to the outlet side of the wheel cylinders Wfr and Wrl to the first hydraulic circuit HC1, and the normally closed outlet valves are connected to the outlet side of the wheel cylinders Wfl and Wrr. The valves OUT3 and OUT4 are connected. The normally open outlet valves OUT1, OUT2, OUT3, and OUT4 may be driven when the brake fluid pressure in each wheel cylinder Wfr, Wrl, Wfl, and Wrr is reduced.

A low pressure accumulator (LPA1) for temporarily storing the brake fluid discharged from the wheel cylinders (Wfr, Wrl) of each wheel (FR, RL) is provided at the outlet side of the normally closed outlet valves (OUT1, OUT2), and the normally closed outlet A low pressure accumulator LPA2 for temporarily storing brake fluid discharged from the wheel cylinders Wfl and Wrr of each wheel FL and RR may be provided at the outlet side of the valves OUT3 and OUT4 .

The hydraulic pumps (HP1, HP2) that pump the brake fluid stored in the low-pressure accumulators (LPA1, LPA2) and forcibly reflux to the side of each wheel cylinder (Wfr, Wrl, Wfl, Wrr), and the hydraulic pumps (HP1, HP2) connected to the A motor M is provided.

Here, a normally open (NO: Normal Open) valve opens the valve flow path before energization and closes the valve flow path when energized, and a normally closed (NC: Normal Close) valve closes the valve flow path before energization and closes the valve flow path when energized. can be opened

The vehicle brake control device having the above configuration controls the operation of the inlet valve (IN1-IN4), the outlet valve (OUT1-OUT4) and the motor (M) during ABS control to control each wheel cylinder (Wfr, Wrl, Wfl, Wrr) can increase, maintain, or depressurize the brake fluid pressure of

When the brake pressure of the wheel cylinders (Wfr, Wrl, Wfl, Wrr) is increased, the inlet valves (IN1-IN4) are opened, the outlet valves (OUT1-OUT4) are closed, and the brake fluid with increased brake pressure The hydraulic pumps HP1 and HP2 are operated by driving the motor M to be supplied to the cylinders Wfr, Wrl, Wfl, and Wrr. Due to this, the brake pressure of the wheel cylinders Wfr, Wrl, Wfl, and Wrr may be increased. As the brake hydraulic pressure in the wheel cylinders Wfr, Wrl, Wfl, and Wrr increases, the brake caliper 39 may operate.

When maintaining the brake pressure of the wheel cylinders (Wfr, Wrl, Wfl, Wrr), the inlet valves IN1-IN4 and the outlet valves OUT1-OUT4 are closed, respectively. Due to this, the brake pressure of the wheel cylinders Wfr, Wrl, Wfl, and Wrr can be maintained.

When the brake pressure of the wheel cylinders (Wfr, Wrl, Wfl, Wrr) is reduced, the motor (M) is stopped to stop the hydraulic pumps (HP1, HP2), and the inlet valves (IN1-IN4) are closed, By opening the outlet valves (OUT1-OUT4), the brake fluid is discharged from the wheel cylinders (Wfr, Wrl, Wfl, Wrr) to the low-pressure accumulators (LPA1, LPA2). Due to this, the brake pressure of the wheel cylinders Wfr, Wrl, Wfl, and Wrr can be reduced.

3 illustrates a control block of a brake control apparatus for a vehicle according to an exemplary embodiment.

Referring to FIG. 3 , a brake light switch 35 and a wheel speed sensor 36 may be electrically connected to the input side of the control unit 34 .

The inlet valves IN1-IN4, the outlet valves OUT1-OUT4, and the motor M may be electrically connected to the output side of the controller 34 .

The control unit 34 controls the inlet valves IN1-IN4, the outlet valves OUT1-OUT4 and the motor M during ABS control based on the information detected by the brake light switch 35 and the wheel speed sensor 36. Drives can be individually controlled.

4 illustrates an ABS control cycle in the brake control apparatus for a vehicle according to an exemplary embodiment.

Referring to FIG. 4 , when the driver presses the brake pedal 31 , the brake hydraulic pressure applied to the wheel cylinders increases and the wheel speed decreases. When the difference between the wheel speed and the vehicle speed V increases and the vehicle deceleration drops below a specified value (point A), the control unit 34 determines that the wheel is about to lock. At this time, the controller 34 outputs the pressure reducing signal to the inlet valve IN and the outlet valve OUT to reduce the brake hydraulic pressure (between a and b).

When the vehicle deceleration and wheel speed start to recover and the vehicle speed reaches the point B, the control unit 34 outputs a pressure holding signal to maintain the pressure in the wheel cylinders (between b and c).

When the wheel speed deceleration is further recovered and exceeds the point C, the control unit 34 determines that the wheel locking possibility has been eliminated and increases the brake hydraulic pressure by outputting a pressure increase signal again (between c and d).

The brake pressure is controlled (between d and e) by repeatedly increasing and maintaining the pressure.

Then, the control unit 34 repeats the ABS control cycle to control the brake pressure.

5 is a diagram illustrating a method of controlling a brake control apparatus for a vehicle according to an exemplary embodiment.

Referring to FIG. 5 , in the control method of the vehicle brake control apparatus according to an embodiment, the speed of each wheel is detected ( 100 ), the detected acceleration of each wheel is calculated ( 102 ), and the calculated acceleration of each wheel is calculated. 1st low-pass filtering (104), 2nd low-pass filtering of each wheel acceleration filtered by 1st low-pass filter (106), calculating the jerk amount of each wheel acceleration filtered by 2nd low-pass filtering (108), and controlling It is determined whether the jerk amount of the corresponding wheel, which is the target wheel, is equal to or greater than a preset value (Thr) (110), and if the jerk amount of the corresponding wheel is equal to or greater than the preset value (Thr), it is determined whether the corresponding wheel is ABS inactive (112), If the corresponding wheel is ABS non-operating, it is determined whether the brake light switch 35 is in the ON state (114), and if the brake light switch 35 is in the ON state, the second low-pass filtered corresponding Determine the road friction coefficient of the wheel based on the wheel acceleration (116), estimate the vehicle speed by applying the determined road friction coefficient (118), and if the jerk amount of the corresponding wheel is not greater than or equal to the preset value (Thr), or When the wheel is in ABS operation or the brake light switch 35 is OFF, the road friction coefficient of the wheel is determined as the road friction coefficient corresponding to the high friction road surface (120), and the determined road friction coefficient is applied and estimating the vehicle speed ( 118 ).

The control unit 34 calculates the acceleration of each wheel by differentiating each of the wheel speeds detected through each wheel speed sensor 36 .

The controller 34 low-pass filters the calculated acceleration of each wheel using the low-pass filter. Since the signal detected from each wheel speed sensor 36 is noisy, the wheel acceleration value obtained by differentiating the wheel speed value also contains a lot of noise. The controller 34 removes noise from the wheel acceleration by using the first low-pass filter.

The control unit 34 may perform secondary low-pass filtering using a second low-pass filter that is a preset low-pass filter to convert the first low-pass filtered wheel acceleration into a road friction coefficient.

The control unit 34 calculates the jerk amount of each wheel acceleration filtered by the second low pass. The control unit 34 calculates a jerk amount that is a change in wheel acceleration by subtracting the second low-pass filtered previous wheel acceleration from the second low-pass filtered current wheel acceleration (filtered acceleration new). The amount of jerk of the wheel can be used as an indicator of how quickly the change in wheel acceleration increases.

If the second low-pass filtered jerk amount of the corresponding wheel is higher than the preset value Thr, the ABS is not operating in which pressure control for the corresponding wheel is not performed, and the brake light switch 35 is on , determine the road friction coefficient of the corresponding wheel based on the second low-pass-filtered wheel acceleration. At this time, since the determined coefficient of road friction is determined for every four wheels, it is possible to determine a total of four coefficients of road friction. The control unit 34 determines the lowest road friction coefficient among the road friction coefficients of the four wheels as the road friction coefficient of the corresponding wheel. When the lowest coefficient of friction is selected, better stability can be secured in Split Mu with different coefficients of friction, and even if there is a large error in road surface estimation, the stability of ABS control can be secured.

The controller 34 estimates the vehicle speed by applying the determined coefficient of road friction. In this case, the control unit 34 uses the determined road friction coefficient as a slope limit value of the estimated vehicle speed.

If the amount of jerk of the corresponding wheel is not equal to or greater than the preset value Thr, the corresponding wheel is ABS, or the brake light switch 35 is OFF, the control unit 34 adjusts the road friction coefficient of the corresponding wheel. It is determined as a road friction coefficient corresponding to the high friction road surface ( 120 ), and the vehicle speed is estimated by applying the determined road friction coefficient.

6 is a diagram illustrating a control timing of a brake control apparatus for a vehicle according to an exemplary embodiment.

Referring to FIG. 6 , description is limited to the right front wheel FR.

When the brake light switch 35 is on, the FR is in a state in which the ABS active flag is not activated, and the secondary low-pass filtered FR jerk amount is higher than a preset value, the condition for estimating the road friction coefficient It is judged that the satisfaction flag has been activated.

If the condition satisfaction flag for estimating the road friction coefficient is activated, the control unit 34 estimates the friction coefficient of the FR corresponding to the second low-pass filtered FR acceleration. At this time, since the road friction coefficients of FL, RL, and RR will be estimated in the same way, the lowest road friction coefficient among the four total road friction coefficients can be finally estimated as the road friction coefficient of FR. This is to secure better stability in Split Mu and to secure the stability of ABS control even if there is a large error in road surface estimation.

On the other hand, if the condition satisfaction flag for estimating the road friction coefficient is not activated, the control unit 34 estimates the friction coefficient of FR as a friction coefficient corresponding to the high friction road surface.

The controller 34 estimates the vehicle speed by using the estimated road friction coefficient as a slope limit value of the vehicle speed to be estimated using the determined road friction coefficient.

Thereafter, the controller 34 may perform ABS control by estimating a wheel slip rate and a vehicle deceleration speed based on the estimated vehicle speed.

By applying the above method, the vehicle speed can be estimated more accurately and reliably in the first cycle of ABS control, thereby improving vehicle stability.

34: control unit 35: brake light switch
36: wheel speed sensor IN1-IN4: inlet valve
OUT1-OUT4: outlet valve

Claims (8)

a brake light switch for detecting operation of a brake pedal;
a wheel speed sensor for detecting the speed of each wheel; and
Calculate wheel acceleration from the wheel speed detected by the wheel speed sensor, low-pass filter the calculated wheel acceleration through a low-pass filter, calculate an amount of wheel jerk from the low-pass filtered wheel acceleration, and the brake A control unit for estimating the road friction coefficient of the control target wheel using the state of the back switch, whether the ABS control of the control target wheel is operating, and the calculated wheel jerk amount, and estimating the vehicle speed from the estimated road friction coefficient The vehicle's brake control system. According to claim 1,
When the brake light switch is on, the control target wheel is ABS, and the calculated wheel jerk is higher than a preset value, the control unit may control the road surface of the control target wheel based on the low-pass filtered wheel acceleration. A vehicle braking control device that estimates the friction coefficient. 3. The method of claim 2,
The control unit finally estimates the lowest coefficient of road friction among the estimated coefficient of friction and the coefficient of friction of other wheels as the coefficient of friction of the wheel to be controlled. According to claim 1,
When the brake light switch is turned off, the control target wheel is in ABS operation, or the calculated wheel jerk is lower than a preset value, the control unit sets the road friction coefficient of the control target wheel to a high friction road surface. A vehicle braking control device that is estimated by the coefficient of road friction. Calculate the wheel acceleration from the wheel speed detected by the wheel speed sensor,
Low-pass filtering the calculated wheel acceleration through a low-pass filter,
calculating the amount of wheel jerk from the low-pass filtered wheel acceleration,
Estimating the road friction coefficient of the control target wheel using the state of the brake light switch, whether ABS control is operating on the control target wheel, and the calculated wheel jerk amount,
A control method of a vehicle brake control apparatus for estimating a vehicle speed from the estimated road friction coefficient. 6. The method of claim 5,
Estimating the road friction coefficient is based on the low-pass filtered wheel acceleration when the brake light switch is on, the control target wheel is not in operation, and the calculated wheel jerk is higher than a preset value. A control method of a vehicle brake control apparatus for estimating a road friction coefficient of the control target wheel. 7. The method of claim 6,
The estimating of the road friction coefficient includes finally estimating the lowest road friction coefficient among the estimated road friction coefficient and the road friction coefficients of other wheels as the road friction coefficient of the control target wheel. 6. The method of claim 5,
The estimating of the road friction coefficient includes determining the road friction coefficient of the control target wheel when the brake light switch is turned off, the control target wheel is in operation of ABS, or the calculated wheel jerk is lower than a preset value. A control method of a vehicle braking control device estimating a road friction coefficient corresponding to a high friction road surface.

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