KR20020037159A - Method of traction control system for vehicle - Google Patents

Abstract

PURPOSE: A traction control method for a vehicle is provided to obtain proper accelerating ability by deciding road gradient and controlling the slip rate according to the road gradient. CONSTITUTION: In a traction control method for a vehicle calculating the wheel speed, the wheel acceleration, the vehicle body speed, and the vehicle body acceleration according to the output signals of a wheel speed sensor, first deciding traction mode(S130) on the basis of the present slip rate of the vehicle calculated from the wheel speed and the vehicle body speed is performed. In case of traction mode, gradient of road is decided on the basis of the wheel acceleration to the vehicle body acceleration(S140). Predetermined reference slip rate is decided according to the decided gradient of road(S150). After comparing the reference slip rate with the present slip rate of the vehicle(S160), to make the slip rate of the vehicle reach the reference slip rate, hydraulic pressure supplied to the wheel cylinder is controlled.

Description

Vehicle traction control system {Method of traction control system for vehicle}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a traction control system for a vehicle, and determines an inclination of a road surface during traction control, and uses the traction control system to adjust a slip rate of a current vehicle according to the inclination of a road surface, thereby ensuring proper acceleration performance. It relates to a vehicle traction control method for enabling.

In general, when a vehicle accelerates a vehicle, the traction system does not control the driving wheel of the vehicle by the driver's accelerator control (typically, the slip ratio is a characteristic between the tire and the road surface (drive wheel speed-body speed) / drive wheel). The speed is divided by a percentage) to ensure a stable slip ratio in the traction control region to ensure sufficient cornering force and driving force. Accordingly, the torque for the driving wheel is controlled to obtain an optimum slip ratio by the driving wheel brake control, so that the driving wheel does not turn when starting and accelerating on the slippery road surface, thereby obtaining the optimum driving force according to the road surface condition.

As a conventional traction control method, the BTCS (Brake Traction Control System) is used, and the brake control system (BTCS) mainly detects the speeds of the left and right driving wheels, and when the speed difference exceeds the reference value, the brake hydraulic pressure is supplied to each wheel. This is to increase the braking force applied to the driving wheel.

However, in the conventional vehicle traction control method, when the vehicle is accelerated on the inclined road surface, the traction control is performed in a state where the minimum slip is set so that the engine output does not stop based on the maximum slope of the road surface. There is a problem that does not obtain a proper acceleration force, in particular, the slip does not accelerate on a road surface with a large slope, such as hills, is generated.

The present invention is to solve the above problems, an object of the present invention is to determine the inclination of the road surface, and provides a vehicle traction control method to ensure the proper acceleration performance by adjusting the slip ratio according to the slope of the road surface. It is.

1 is a block diagram of a traction control method for a vehicle according to the present invention.

2 is a flowchart illustrating a vehicle traction control method according to the present invention.

3 is a flowchart illustrating a method of determining a slope and a reference slip ratio of a road surface of a current vehicle.

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

10: wheel speed sensor 20: electronic control unit

21: wheel speed calculation unit 22: wheel acceleration operation unit

23: body acceleration operation unit 24: body acceleration operation unit

30: hydraulic valve drive unit 31: front left wheel

32: front right wheel 33: rear left wheel

34: rear right wheel 40: storage unit

The present invention for achieving the above object in the vehicle traction control method for calculating the wheel speed, wheel acceleration, body speed, body acceleration in accordance with the output signal of the wheel speed sensor, the current vehicle calculated from the wheel speed and the body speed Determining whether the vehicle is in the traction mode based on the slip ratio of the vehicle, determining the inclination of the road surface based on the wheel acceleration relative to the vehicle acceleration in the traction mode, and determining a predetermined reference slip according to the determined road slope. Determining a rate, and adjusting the hydraulic pressure supplied to the wheel cylinder so that the slip rate of the vehicle reaches the reference slip rate by comparing the set reference slip rate with a current slip rate of the vehicle. do.

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

2 is a block diagram of a traction control method for a vehicle according to the present invention. As shown in FIG. 2, the wheel speed sensor 10 for detecting the wheel speed is electrically connected to the electronic control unit 20 for performing overall control of the vehicle, and the front left wheel FL of the vehicle 31. , The hydraulic valve driver 30 for controlling the brake hydraulic pressure supplied to the front right wheel FF 32, the rear left wheel RL 33, and the rear left wheel RR 34, and a control program are stored. The storage unit 40 is electrically connected to the electronic control unit 20.

The electronic control unit 20 includes a wheel speed calculating unit 21 for calculating a wheel speed according to the detection signal of the wheel speed sensor 10, and a wheel acceleration calculating unit 22 for calculating wheel acceleration according to the calculated wheel speed. And a body speed calculating section 23 for estimating the body speed according to the wheel speed, and a body acceleration calculating section 24 for calculating the body acceleration according to the calculated body speed.

In addition, the storage unit 40 applies a predetermined hydraulic pressure to the respective wheels for a predetermined time through the hydraulic valve driving unit 30 by the electronic control unit 20 for each slope of the road surface, and then set a predetermined body acceleration (the amount of increase in the body speed). The measured values of the wheel acceleration values required to reach the data are stored, and the data on the optimum reference slip ratio to minimize the slip phenomenon (slip phenomenon) at that time are stored.

For example, the data may include a first road slope and a first reference slip rate in the first range of wheel acceleration values, a second road slope and a second reference slip rate in the second range, and a third in the third range. If the road slope and the third reference slip rate and the third range is not in the third range, the slope and the reference slip rate of the road surface are set to correspond to the wheel acceleration values in the same manner as the fourth slope and the fourth reference slip rate. And the first range of the wheel acceleration is lower than the second range, and the second range is lower than the third range. In addition, the first road slope is less than the second road slope, the second road slope is less than the third road slope, the third road slope is less than the fourth road slope, and the first reference slip ratio is second. It is less than the reference slip rate, the second reference slip rate is less than the third reference slip rate, and the third reference slip rate is set to be less than the fourth reference slip rate.

In the embodiment of the present invention, the slope of the road surface is divided into four cases for convenience of description, but the number is not limited. In addition, in the embodiment of the present invention, setting the reference slip rate to one value has been described, but may be set to a predetermined range value instead of one value.

2 is a flowchart illustrating a vehicle traction control method according to the present invention. As shown in FIG. 2, when the vehicle runs in a state in which slopes and reference slip rates of a plurality of road surfaces are preset in the storage unit 40 so as to correspond to each of a range of wheel acceleration values, the wheels as before. The speed sensor 10 detects the speed for each wheel (S100), and transmits the detected signal to the electronic control unit 20 so that the electronic control unit 20 according to the detection signal wheel speed, wheel acceleration, vehicle body The speed, the body acceleration is calculated (S110).

Subsequently, the electronic control unit 20 substitutes the slip rate calculation formula ((wheel speed-body speed) * 100 / wheel speed [%]) using the wheel speed and the body speed to calculate the current slip rate, and is currently driving. Slip rate of the vehicle is calculated (S120).

Thereafter, the electronic control unit 20 compares the calculated slip rate of the current vehicle with the slip rate at the instant of the traction control, that is, the threshold of the slip rate preset by the experiment, to determine whether it is in the traction control mode, If the calculated slip ratio exceeds the threshold, it is determined as a traction control mode (S130).

When it is determined in the determination step (S130) that the traction control mode, the electronic control unit 20 is the wheel acceleration value is stored in the storage unit 40 to determine the inclination of the road surface that the vehicle is currently driving It is determined in which range of the value range, and according to the determination result, the slope of the stored road surface corresponding to the range including the calculated wheel acceleration is determined as the slope of the road surface on which the vehicle currently runs (S140). In addition, when the slope of the road surface of the current vehicle is determined, a predetermined reference slip ratio is determined according to the slope of the road surface (S150) (in the embodiment of the present invention, the slope of the road surface is determined in advance according to the range of the wheel acceleration value before shipping). Although the setting is explained, it may be set based on the wheel acceleration and the body acceleration while the vehicle is running without setting in advance).

The electronic control unit 20 compares the magnitude of the slip rate of the current vehicle and the reference slip rate in order to control the slip ratio of the currently running vehicle to the set reference slip ratio, and according to the comparison result, the hydraulic valve driving unit 30. To adjust the hydraulic pressure.

For example, when the reference slip rate is smaller than the slip rate of the current vehicle (S160), the electronic control unit 20 uses the hydraulic valve driving unit 30 until the current cylinder slip ratio reaches the reference slip rate. Increase the hydraulic pressure supplied to the (S161) so that the slip phenomenon does not occur, if the reference slip rate is greater than the current slip ratio of the vehicle (S170), by reducing the hydraulic pressure supplied to the wheel cylinder (S171) If the reference slip ratio is equal to the slip ratio of the current vehicle, the acceleration performance is maintained, and the hydraulic pressure of the current state is maintained to maintain the current stable state (S180).

3 is a flowchart illustrating a method of determining a slope and a reference slip ratio of a road surface of a current vehicle. As shown in FIG. 3, when the calculated wheel acceleration value is included in the stored first range, it is determined that the slope of the road surface of the vehicle currently being driven is the first road slope (S200), and the determined first road slope In operation S201, the first reference slip rate is set as the reference slip rate for the optimal traction control at.

If the calculated wheel acceleration value is not included in the first range in step S140, the electronic control unit 20 determines whether the calculated wheel acceleration value is included in the second range, and if present, the current vehicle. It is determined that the slope of the road surface is the second road slope (S210), and the second reference slip rate preset for optimal traction control in the determined second road slope is determined as the reference slip rate (S211).

As described above, the first road slope and the second road slope are also determined in a manner of determining the third road slope (S220). If the wheel acceleration value corresponds to the third road slope, the third reference slip ratio is used as a reference slip rate. Determine (S221). If the wheel acceleration value does not correspond to the third road surface slope, the fourth reference slip rate is determined as the reference slip rate (S230).

As described in detail above, the present invention determines the road slope of the currently running vehicle and changes the traction control method using the same to prevent engine output stop due to the traction control, and particularly efficient acceleration performance on a road with a large slope. It is effective to maintain.

Claims (6)

In the vehicle traction control method for calculating the wheel speed, wheel acceleration, body speed, body acceleration according to the output signal of the wheel speed sensor, Determining whether the vehicle is in traction mode based on the slip rate of the current vehicle calculated from the wheel speed and the body speed; In the traction mode, determining a slope of the road surface based on wheel acceleration with respect to the vehicle acceleration; Determining a predetermined reference slip ratio according to the determined road slope; And comparing the set reference slip rate with a slip rate of a current vehicle to adjust the hydraulic pressure supplied to a wheel cylinder so that the slip rate of the vehicle reaches the reference slip rate. The method of claim 1, The road slope determination step may determine whether the calculated wheel acceleration value is included in a first range of a preset wheel acceleration, and if the determination result is included in the first range, the road slope of the current vehicle is stored in the first range. Determining the preset first road surface slope corresponding to If the wheel acceleration value is not included in the first range, it is determined whether the wheel acceleration value is included in the second range of the preset wheel acceleration. If the wheel acceleration value is included in the second range, the current slope of the current vehicle is determined. Determining a preset second road surface slope corresponding to the stored second range; If the wheel acceleration value is not included in the second range, it is determined whether the wheel acceleration value is included in the third range of the preset wheel acceleration. If the wheel acceleration value is included in the third range, the road surface slope of the current vehicle is determined. And determining the preset third road surface slope corresponding to the stored third range. The method of claim 2, The first range is a range of wheel acceleration value lower than the second range, the second range is a range of wheel acceleration value lower than the third range, the first road surface slope is less than the second road surface slope, And the second road surface slope is less than the third road surface slope. The method according to claim 1 or 2, In the step of setting the reference slip rate, if the slope of the road surface of the current vehicle is the first road slope, the preset first slip rate is set; if the second road slope is the second slip rate, the preset second slip rate; And the reference slip rate is set to a fourth slip rate if the third slip rate is not the third road surface slope. The method of claim 4, wherein The first reference slip rate is less than the second reference slip rate, the second reference slip rate is less than the third reference slip rate, and the third reference slip rate is less than the fourth reference slip rate. Vehicle traction control method. The method of claim 1, The hydraulic pressure adjusting step includes increasing the hydraulic pressure supplied to the wheel cylinder until the slip ratio of the vehicle reaches the reference slip ratio when the slip ratio of the vehicle is greater than the reference slip ratio; Reducing the hydraulic pressure supplied to the wheel cylinder until the slip ratio of the vehicle reaches the reference slip ratio when the slip ratio of the vehicle is smaller than the reference slip ratio; And maintaining the hydraulic pressure supplied to the wheel cylinder when the slip ratio of the vehicle is equal to the reference slip ratio.