KR20050019980A - System for controlling the stability of vehicles - Google Patents

Abstract

PURPOSE: An electronic stability control system of a vehicle is provided to prevent unnecessary loss of braking power on a low-friction road by executing sudden braking controls if road frictional coefficient is decided to indicate high or middle-friction road by a sudden braking control unit and restricting the sudden braking control on the low-friction road. CONSTITUTION: An electronic stability control system of a vehicle is composed of a master cylinder(20) for forming braking pressure generated by operating a brake pedal(10) by a driver; a pressure sensor(1) for measuring discharge hydraulic pressure of the master cylinder; lateral and longitudinal acceleration sensors for measuring deceleration and acceleration of horizontal and vertical axes in traveling; plural TC(Traction Control) valves(47) for opening and closing the discharge hydraulic pressure of the master cylinder toward a wheel cylinder; plural solenoid valves(42) for executing a braking operation by cutting off and opening the hydraulic pressure exhausted from the master cylinder toward the wheel cylinder; a pump(44) for sucking and feeding the hydraulic pressure applied on the wheel cylinder to the master cylinder; a motor(45) for driving the pump; an oil suction passage(48a) for guiding the oil of the master cylinder to flow into an inlet of the pump in a TCS(Traction Control System) mode; a shuttle valve(48) disposed in the oil suction passage to open and shut the suction passage; and a control unit(2) for judging sudden braking control for an emergency braking state by inputting sensing values of the lateral and longitudinal acceleration sensors and the pressure sensor and outputting a sudden braking control signal by using the estimated road frictional coefficient.

Description

System for controlling the stability of vehicles}

The present invention relates to a stability control system of a vehicle, and more particularly, to a stability control system of a vehicle equipped with an auxiliary braking system for assisting when a sufficient braking pressure by a driver does not occur.

In general, the anti-lock brake system (hereinafter referred to as ABS) is to prevent the wheel from locking by appropriately adjusting the braking pressure applied to the wheel according to the slip ratio calculated from the wheel speed. The TCS (hereinafter referred to as TCS) is to control the driving force of the engine to prevent excessive slippage during sudden start or acceleration of the vehicle.

The anti-lock brake system (ABS) and traction control system (TCS) can perform well when the vehicle is driving on a straight road, but when steered on a curve road, the understeer is excessively inclined outward. Can occur and, conversely, over steer can occur that is excessively inward.

Therefore, there is a demand for a vehicle stability system (hereinafter referred to as an electronic stability program ESP) to stably control a vehicle's posture under any circumstances in which the vehicle travels, that is, to prevent steering loss of the vehicle. For example, in a situation where an under steer is pushed out of a desired driving trajectory when turning, a braking force is applied to the rear wheels to prevent the vehicle from being pushed outward and the turning speed of the vehicle is increased. In a situation where an excessively large oversteer is inclined inward on a desired driving trajectory, a braking force is required to the front wheels.

In order to control vehicle stability during turning, the performance of the system is determined by accurately predicting the turning speed of the driver's desired vehicle and by applying the appropriate braking pressure to the front and rear wheels to drive the vehicle according to the predicted turning speed. .

In addition, in controlling the stability of the vehicle, the performance of the above-described ABS and TCS should not be impaired. On the contrary, the stability of the vehicle is not adversely affected by the ABS and the TCS. Therefore, in order to control the safety of the vehicle appropriately in the state of movement of the vehicle, it is desirable to focus on cooperative control in conjunction with the existing ABS and TCS.

The conventional vehicle stability system as described above reduces the vehicle speed by forming a braking pressure on the wheel of the vehicle when the driver operates the brake pedal. However, the elderly and female drivers do not form sufficient operating force in a situation where rapid braking is to be performed. There is a problem that the braking distance is long. In order to solve such a problem, a Brake assist system (BAS) is provided. Referring to FIG. 1, the auxiliary braking system will be briefly described as follows.

If a sudden braking condition occurs by the driver in an emergency situation, the TC valve 47 is closed, the shuttle valve 48 is opened to form a suction flow path 48a, and the motor 45 is driven to operate the hydraulic pressure of the master cylinder 20. Is applied directly to the wheel cylinder 30 is to perform the braking control.

However, the conventional auxiliary braking system as described above requires the operation of the auxiliary braking system on a low friction road surface having a low slip generating braking pressure in which the wheels are locked as the road is in a state of the road, that is, the frictional force is not considered. Even when none is generated, unnecessary braking force is generated.

As the unnecessary braking force is generated as described above, the braking force loss is caused, and the user has an unpleasant feeling due to the braking noise and vibration generated due to the braking force not expected.

The present invention to solve the above problems in the emergency braking system is performed, the vehicle stability control system for estimating the friction coefficient of the road surface and controlling the driving of the auxiliary braking system using the estimated road friction coefficient Provide it.

The present invention for achieving the above object,

Determining whether the emergency braking situation is present; determining whether the emergency braking condition is a sudden braking control condition; estimating a friction coefficient of the road surface by using the longitudinal and lateral acceleration values in the case of the sudden braking control condition; The rapid braking control is performed according to the friction coefficient of the road surface.

The step of determining whether the emergency braking situation comprises a step of determining whether the discharge pressure change rate of the master cylinder is greater than the set value, and if the discharge pressure value of the current master cylinder is greater than or equal to the set value is determined as an emergency braking situation. do.

The step of determining whether the sudden braking control condition is characterized in that the emergency braking control condition is determined if the rate of change of the discharge pressure of the master cylinder is less than the set value in the emergency braking situation.

The step of estimating the friction coefficient of the road surface by using the longitudinal and lateral acceleration values is characterized in that it is performed using a predetermined equation.

The step of estimating the friction coefficient of the road surface by using the longitudinal and lateral acceleration values is characterized in that it is performed by using the longitudinal and lateral acceleration values at the time determined as the emergency braking situation.

The step of performing the rapid braking control is characterized in that the sudden braking control is performed only when the estimated friction coefficient is greater than or equal to a preset value.

The configuration of the present invention for performing the above operation,

A master cylinder for forming braking pressure according to the driver operating the brake pedal, a pressure sensor for measuring the pressure of the discharge hydraulic pressure of the master cylinder, and a lateral acceleration for measuring the deceleration of each of the horizontal and vertical axes when the vehicle is running. A sensor, a longitudinal acceleration sensor, a plurality of TC valves for opening and closing the discharge hydraulic pressure of the master cylinder to the wheel cylinder side, and blocking and opening the hydraulic pressure discharged from the master cylinder to the wheel cylinder side to perform a braking operation. A plurality of solenoid valves, a pump for sucking and supplying hydraulic pressure applied to the wheel cylinder to the master cylinder, a motor for driving the pump, and oil for guiding the oil of the master cylinder to be sucked into the pump inlet in the TCS mode The suction flow path and the oil suction flow path are configured to open and close the suction flow path. In a vehicle configured with a shuttle valve, the sensing values of the lateral acceleration sensor, the longitudinal acceleration sensor, and the pressure sensor are input to determine whether to perform sudden braking control when an emergency braking situation occurs and to estimate the frictional force of the road surface. And a controller for outputting a rapid braking control signal using a friction coefficient.

The control unit inputs a sensing value of the pressure sensor to determine the occurrence of an emergency situation, and determines whether it is a sudden braking control condition and outputs a control signal, the sensing value of each of the longitudinal acceleration sensor, the lateral acceleration sensor A road friction coefficient estimator for estimating a friction coefficient of a road surface and a road friction coefficient estimated by inputting a road friction coefficient estimated by the road friction coefficient estimator when a rapid braking control start signal is input by the sudden braking determination unit. It is characterized by consisting of a rapid braking control unit for outputting a signal for the rapid braking control if the set value or more.

Hereinafter, the detailed configuration and operation of the present invention will be described with reference to the accompanying drawings.

1 is a hydraulic circuit diagram showing a configuration of an electronically controlled brake system for a vehicle according to the present invention, Figure 2 is a block diagram showing the configuration of a control unit according to the present invention, Figure 3 is a control flowchart of the present invention.

First, referring to the hydraulic circuit with reference to FIG.

Electronically controlled brake system for a vehicle according to the present invention is connected to the primary port 21 of the master cylinder 20 and two wheel cylinders 30 to control the hydraulic pressure transmission 40A and the master cylinder ( A secondary hydraulic circuit 40B for connecting the secondary port 22 and the remaining two wheel cylinders 30 to control hydraulic pressure transmission, and a controller (see FIG. 2; And these are compactly installed in the modulator block 40.

The primary hydraulic circuit 40A and the secondary hydraulic circuit 40B are solenoid valves 41 and 42 for controlling braking hydraulic pressure transmitted to two wheel cylinders 30, respectively, and the wheel cylinder 30. A pump 44 for sucking and pumping oil from the oil or master cylinder 20 discharged from the side, a low pressure accumulator 43 for temporarily storing the oil exiting the wheel cylinder 30, and the pump 44 from the pump 44. A high pressure accumulator 46 for reducing pressure pulsation from the hydraulic pressure being pumped, and an oil suction passage 48a for guiding the oil of the master cylinder 20 to be sucked into the inlet of the pump 44 in the TCS mode.

The plurality of solenoid valves 41 and 42 are associated with the upstream and downstream sides of the wheel cylinders 30, which are normally open solenoid valves disposed upstream of each wheel cylinder 30 and kept in an open state. (41) and a normal closed solenoid valve 42 disposed downstream thereof and kept normally closed. The opening / closing operation of the solenoid valves 41 and 42 is controlled by the control unit 2 which detects the vehicle speed through a wheel sensor (not shown) disposed on each wheel side, and the normally open solenoid valve 42 according to the decompression braking. ) Is opened and the oil exiting from the wheel cylinder 30 side is temporarily stored in the low pressure accumulator 43.

The pump 44 is driven by the motor 45 to suck the oil stored in the low pressure accumulator 43 and discharge it to the high pressure accumulator 46 side (in ABS boosting or holding mode), so that the hydraulic pressure is transferred to the wheel cylinder 30 side or the like. The transfer to the master cylinder 20 side.

In addition, an NO solenoid valve 47 (hereinafter referred to as TC valve) for traction control control is provided in the main flow passage 47a connecting the master cylinder 20 and the outlet of the pump 44. The TC valve 47 is normally kept open, and the braking hydraulic pressure generated in the master cylinder 20 during normal braking through the brake pedal 10 is transmitted to the wheel cylinder 30 through the main flow passage 47. .

In addition, the oil suction flow passage 48a branches from the main flow passage 47 to guide the oil of the master cylinder 20 to be sucked to the inlet side of the pump 44, where the oil flows only into the pump 44 inlet. Shuttle valve 48 is provided. That is, the electrically operated shuttle valve 48 is installed in the middle of the oil suction flow path 48a, and is normally closed and operates to open in the TCS mode.

Moreover, the pressure sensor 1c for measuring the discharge pressure of the said master cylinder 20 is comprised.

In addition, although not shown in FIG. 1, a lateral acceleration sensor 1a and a longitudinal acceleration sensor 1b are configured to measure deceleration rates on the lateral and longitudinal sides of the vehicle when the vehicle is traveling.

As shown in FIG. 2, the controller 2 is

The emergency braking determination unit 2a outputs a control signal by judging occurrence of an emergency situation by inputting a sensing value of the pressure sensor 1c, and determining whether it is a sudden braking control condition, and the respective longitudinal acceleration sensors 1b and lateral accelerations. The road surface friction coefficient estimator 2b for estimating the friction coefficient of the road surface by inputting the sensing value of the sensor 1a, and the road surface friction coefficient estimator 2b when a rapid braking control start signal is input from the sudden braking determination unit 2a. And a road braking control unit 2c for inputting a road surface friction coefficient estimated in step 2) and outputting a signal for sudden braking control when the road surface friction coefficient input is equal to or larger than a set value.

In the control process of the present invention configured as described above, as shown in FIG. 3, determining whether the current emergency braking situation is performed; determining whether the emergency braking control condition is a sudden braking control condition; Estimating a friction coefficient of the road surface using a lateral acceleration value, and performing rapid braking control according to the estimated friction coefficient of the road surface.

The detailed operation is as follows.

When the brake pedal 10 is operated by the driver and a braking pressure is formed in the master cylinder 20, the controller 2 inputs a braking pressure value detected by the pressure sensor 1c configured in the master cylinder 20.

The sudden braking determination unit 2a of the control unit 2 inputs the pressure value detected by the pressure sensor 1c and calculates a change rate, that is, a slope.

The sudden braking determination unit 2a of the control unit 2 determines whether it is an emergency braking situation by inputting the calculated rate of change of pressure and the pressure value output from the pressure sensor 1c.

First, it is determined whether the calculated change rate is greater than a preset value. That is, it is determined whether the rate of increase of the braking pressure by the driver is greater than or equal to the set value, and if greater than or equal to the set value, it is determined whether the pressure value sensed by the current pressure sensor 1c is greater than or equal to a preset value.

In other words, as described above, the rapid braking determination unit 2a determines that the braking pressure is an emergency braking condition when the rate of increase of the braking pressure and the current pressure value are each equal to or more than a preset value.

When it is determined that the emergency braking situation as described above, the sudden braking determination unit 2a determines whether it is a sudden braking control condition. If the rising pressure change rate is smaller than the preset braking control setting value, the sudden braking control unit 2c is determined. Will output a control signal.

Meanwhile, the road surface friction coefficient estimator 2b uses the data sensed by the lateral acceleration sensor 1a and the longitudinal acceleration sensor 1b at the time when the sudden braking determination unit 2a determines that the sudden braking control is started. The friction coefficient of the road surface is estimated by using the following equation.

[Equation]

Where μ is the surface friction coefficient, ax is the sensing value of the lateral acceleration sensor, and ay is the sensing value of the longitudinal acceleration sensor.

Using the above equation, the road friction coefficient estimating unit 2b estimates the frictional force of the currently running road surface, and the pressure value of the wheel cylinder 30 at the time when it is determined that the emergency situation occurs in the sudden braking determination unit 2a. The road surface friction coefficient estimator 2b detects and uses the road surface friction coefficient estimation unit. That is, the friction coefficient of the road surface is estimated using the braking pressure value of the wheel cylinder 30 when the brake pedal is operated by the driver.

When the sudden braking control signal is input from the sudden braking determination unit 2a, the sudden braking control unit 2c determines whether the sudden braking control is performed using the friction coefficient of the road surface estimated by the road friction coefficient estimating unit 2b. As shown in FIG. 2, when the estimated friction coefficient μ is greater than the first predetermined friction coefficient μ1, the first sudden braking control is performed, and the first and second friction coefficients μ1 and the second friction coefficient are μ2. If present, the second braking control is performed, and if it is smaller than the second set friction coefficient μ2, the general braking control is performed without performing the braking control.

That is, the fact that the estimated friction coefficient (μ) is greater than the first set friction coefficient (μ1) means that the currently running road surface is a high friction road surface, and the first set friction coefficient (μ1) and the second set friction coefficient (μ2) If present, the frictional surface is medium, and if it is smaller than the second set friction coefficient [mu] 2, it means that the surface is low friction.

The sudden braking control unit 2c performs sudden braking control when the estimated friction coefficient of the road surface is determined to be high friction or moderate friction road surface, and does not perform rapid braking control when it is determined to be low friction road surface. This will prevent unnecessary loss of braking force.

 As described above, in the present invention, it is possible to determine whether rapid braking is performed using the friction coefficient of the road surface, so that the braking distance can be shortened by allowing the rapid braking control to be performed only on the high friction or intermediate level friction road surface under the condition of the rapid braking control. However, even in the case of a sudden braking control condition, the low braking control is prevented from being performed to prevent unnecessary braking power loss, and to prevent braking noise and vibration, thereby providing a high quality braking system to the user.

1 is a hydraulic circuit diagram showing the configuration of an electronically controlled brake system for a vehicle according to the present invention.

2 is a block diagram showing the configuration of a control unit according to the present invention;

3 is a control flowchart of the present invention.

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

1: pressure sensor 2: control unit

2a: sudden braking judgment unit 2b: road friction coefficient estimation unit

2c: Rapid braking control unit 2b ': Pressure comparison table

40: hydraulic modulator

Claims (10)

A master cylinder for forming braking pressure according to the driver operating the brake pedal, a pressure sensor for measuring the pressure of the discharge hydraulic pressure of the master cylinder, and a lateral acceleration for measuring the deceleration of each of the horizontal and vertical axes when the vehicle is running. A sensor, a longitudinal acceleration sensor, a plurality of TC valves for opening and closing the discharge hydraulic pressure of the master cylinder to the wheel cylinder side, and blocking and opening the hydraulic pressure discharged from the master cylinder to the wheel cylinder side to perform a braking operation. A plurality of solenoid valves, a pump for sucking and supplying hydraulic pressure applied to the wheel cylinder to the master cylinder, a motor for driving the pump, and oil for guiding the oil of the master cylinder to be sucked into the pump inlet in the TCS mode The suction flow path and the oil suction flow path are configured to open and close the suction flow path. In a vehicle configured with a shuttle valve, The sensing values of the lateral acceleration sensors, the longitudinal acceleration sensors, and the pressure sensors are input to determine whether the emergency braking control is performed in case of an emergency braking situation, estimate the frictional force of the road surface, and use the estimated friction coefficient of the road surface for the rapid braking control signal. Stability control system for a vehicle, characterized in that it comprises a control unit for outputting. The method of claim 1,  The control unit inputs a sensing value of the pressure sensor to determine the occurrence of an emergency situation, and determines whether it is a sudden braking control condition and outputs a control signal, the sensing value of each of the longitudinal acceleration sensor, the lateral acceleration sensor A road friction coefficient estimator for estimating a friction coefficient of a road surface and a road friction coefficient estimated by inputting a road friction coefficient estimated by the road friction coefficient estimator when a rapid braking control start signal is input by the sudden braking determination unit. And a braking control unit for outputting a signal for sudden braking control if the set value is higher than the set value. The method of claim 2, And determining the emergency braking situation of the emergency braking determining unit when the pressure change rate of the pressure sensor is greater than the set value and the detected pressure value is greater than the set value. The method of claim 2, And determining whether the sudden braking control part is a sudden braking control condition is determined as a sudden braking control condition when the rate of change of the pressure sensor is less than or equal to a predetermined value in an emergency braking situation. In the stability control system of a vehicle equipped with a plurality of sensors for detecting the movement information of the vehicle, Determining whether the emergency braking situation is present; determining whether the emergency braking condition is a sudden braking control condition; estimating a friction coefficient of the road surface by using acceleration and deceleration acting on the vertical and horizontal axes of the vehicle, in the case of the emergency braking condition; And performing a rapid braking control using the estimated friction coefficient of the road surface. The method of claim 5, The step of determining whether the emergency braking situation is performed is a step of determining whether the discharge pressure change rate of the master cylinder is greater than the set value, and if the discharge pressure value of the current master cylinder is greater than or equal to the set value, it is determined as an emergency braking situation. Vehicle stability control system, characterized in that. The method of claim 5, And determining whether the sudden braking control condition is an emergency braking control condition if the rate of change of the discharge pressure of the master cylinder is less than or equal to a predetermined value in the emergency braking condition. The method of claim 5, Estimating the friction coefficient of the road surface is achieved by the following equation. [Equation] Where μ is the surface friction coefficient, ax is the sensing value of the lateral acceleration sensor, and ay is the sensing value of the longitudinal acceleration sensor. The method of claim 5 or 8, And estimating the friction coefficient of the road surface by using the deceleration of the horizontal axis and the vertical axis at the time determined as the emergency braking condition. The method of claim 5, The determining of whether to perform the sudden braking control is a stability control system of the vehicle, characterized in that for performing a sudden braking control when the estimated coefficient of friction of the road surface is more than a predetermined value.