KR20150071568A - System and method for autonomous emergency braking - Google Patents

Abstract

An automatic emergency braking system and a method thereof are disclosed. According to an embodiment of the present invention, the method of automatic emergency braking comprises the steps of: calculating the required braking force of automatic braking based on the TTC (Time To Collision) with a leading vehicle and the relative speeds of the leading vehicle and a self-vehicle; and performing automatic braking of the self-vehicle using a motor only or synchronously using the motor and a hydraulic brake in accordance with the magnitude of available braking force of the motor and the required automatic braking force.

Description

[0001] The present invention relates to an automatic emergency braking method and system,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic emergency braking method and system, and more particularly, to an automatic emergency braking method and system capable of automatically generating an emergency braking force using a motor when a TTC arrives.

A hybrid vehicle refers to a vehicle that is driven by combining two or more different kinds of power sources efficiently and is usually driven by an engine that obtains a rotational force by burning fuel and a drive motor that obtains a rotational force by the power of a high voltage battery.

Such a hybrid vehicle is capable of reducing exhaust gas by using not only an engine but also a driving motor as an auxiliary power source, thereby improving fuel efficiency. Therefore, more active research is being conducted in response to the demand for the development of environmentally friendly products .

The hybrid vehicle includes an EV (Electric Vehicle) mode, which is a pure electric vehicle mode using only the driving motor power, an HEV (Hybrid Electric Vehicle) mode, which uses the rotational force of the engine as the main driving force and the rotational power of the driving motor as auxiliary driving force, And a regenerative braking (RB) mode in which braking and inertia energy are recovered through power generation of the drive motor to charge the battery when the vehicle is driven by inertia.

In other words, in a hybrid vehicle, the mechanical energy of the engine and the electric energy of the battery are used together, the optimum operating region of the engine and the driving motor is utilized, and energy is recovered by the driving motor at the time of braking.

Such a hybrid vehicle is equipped with a hybrid control unit (HCU), and a controller is provided for each device constituting the system. For example, an engine control unit (ECU) for controlling the overall operation of the engine, a motor control unit (MCU) (including an inverter) for controlling the overall operation of the drive motor, a transmission controller (TCU), a battery management system (BMS) for monitoring and managing the battery status, and a full auto temperature controller (FATC) for controlling the temperature of the room. The HCU is a top-level controller responsible for driving control of each controller, setting of a hybrid operation mode, and overall control of the vehicle. Each of the controllers is connected to a high-speed CAN communication line around the HCU as a top- The upper controller is configured to transmit the command to the lower controller.

1 is a view schematically showing a configuration of a general hybrid vehicle. As shown in Fig. 1, the hybrid vehicle may include an engine 10, a drive motor 20, and an automatic transmission 30. The engine 10 and the drive motor 20 are connected to each other via the engine clutch 50 such that the drive motor 20 and the automatic transmission 30 are directly connected to each other. An integrated starter generator (ISG) 40, which provides a rotational force to the engine 10 (i.e., outputs a cranking torque) at startup, is connected to the engine 10.

The hybrid vehicle enters the regenerative braking traveling mode during braking, at which time the driving motor 20 generates a reverse torque in the rotational direction (reverse torque), thereby generating electric energy. That is, the drive motor 20 performs power generation using the regenerative energy of the vehicle to charge the high-voltage battery. In this case, the drive motor rotates in a state in which reverse torque is applied.

The deceleration force at the braking during running in the hybrid vehicle can be expressed by the sum of the brake braking force and the motor reverse torque. The brake braking force means a braking force to generate a braking device constituted by a wheel in the same manner as in a conventional vehicle by using the hydraulic pressure and the motor reverse torque means a torque in a direction opposite to the traveling direction of the vehicle.

In addition, the application of the automatic emergency braking (AEB) system to prevent collision by automatically braking when the collision with a car is recognized by recognizing the speed and position of the preceding vehicle as a sensor such as a radar or a camera is expanded . The automatic emergency braking system has a time to collision (TTC) as a factor, and if the TTC is too short, there is not enough braking time to increase the probability of collision, This can cause discomfort due to frequent automatic braking. If the vehicle speed is high, a greater braking force is required to braking the vehicle. In order to exert a braking force with a large brake force, a large hydraulic pressure must be present. Since the braking force is not generated while the hydraulic pressure is being generated without the hydraulic pressure, (Prefilled) and ready for immediate braking if necessary. This pre-fill substantially increases the TTC resulting in frequent automatic braking feelings being transmitted to the driver causing inconvenience.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an automatic emergency braking method and system capable of automatically generating an emergency braking force by using a motor at the time of arrival of a TTC without pre- do.

The automatic emergency braking method according to the embodiment of the present invention calculates the required automatic braking braking force based on the time to collision (TTC: time to collision with the preceding vehicle) and the relative speed between the preceding vehicle and the preceding vehicle ; The method may include using only the motor in accordance with the available braking force of the motor and the required size of the automatic braking force, or automatically braking the vehicle using the motor and the hydraulic brake at the same time.

And determining whether the available braking force of the motor is greater than a preset reference value before the automatic braking step.

The available braking force of the motor is calculated based on a torque limit value of the motor and a charging limit value of a battery that supplies power to the motor.

And transmitting a braking command to the motor when the TTC is less than a predetermined time.

The step of automatically braking the vehicle may be a step of automatically braking the vehicle using only the motor when the available braking force of the motor is greater than the required automatic braking force.

Wherein the step of automatically braking the vehicle is a step of automatically braking the vehicle using the motor and the hydraulic brake at the same time when the available braking force of the motor is smaller than the required automatic braking force have.

The method may further include increasing the braking force of the hydraulic brake by the reduced motor braking force when the electric component including the motor and the battery does not operate normally during the automatic braking using the motor.

And adjusting the braking torque of the motor to 0 or increasing the braking force of the hydraulic brake when a wheel lock occurs in a wheel of the vehicle during automatic braking using the motor.

An automatic emergency braking system according to an embodiment of the present invention includes a hydraulic brake; A drive motor; And calculating a required automatic braking force based on a time (TTC: time to collision) between the preceding vehicle and the preceding vehicle, and a relative speed between the preceding vehicle and the preceding vehicle, The control unit may use only the driving motor in accordance with the magnitude of the braking force, or may automatically brake the vehicle by using the driving motor and the hydraulic brake at the same time.

In automatic emergency braking, it is not necessary to perform the pre-fill control by braking by the drive motor, so that it is possible to minimize the operation noise caused by the pre-fill and the operation feeling due to the automatic emergency braking.

If an object suddenly appears, it can not be pre-piled, so that it can braked by the braking force of the motor while raising the brake's hydraulic pressure in case of sudden braking.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to more fully understand the drawings recited in the detailed description of the present invention, a detailed description of each drawing is provided.
2A and 2B are graphs showing the operation of an existing automatic emergency braking system using only the brake hydraulic pressure and the operation of the automatic emergency braking system according to an embodiment of the present invention.
3 is a flowchart illustrating an automatic emergency braking method according to an embodiment of the present invention.

Specific structural and functional descriptions of the embodiments of the present invention disclosed herein are for illustrative purposes only and are not to be construed as limitations of the scope of the present invention. And should not be construed as limited to the embodiments set forth herein or in the application.

The embodiments according to the present invention are susceptible to various changes and may take various forms, so that specific embodiments are illustrated in the drawings and described in detail in this specification or application. It is to be understood, however, that it is not intended to limit the embodiments according to the concepts of the present invention to the particular forms of disclosure, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

The terms first and / or second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are intended to distinguish one element from another, for example, without departing from the scope of the invention in accordance with the concepts of the present invention, the first element may be termed the second element, The second component may also be referred to as a first component.

It is to be understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, . On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between. Other expressions that describe the relationship between components, such as "between" and "between" or "neighboring to" and "directly adjacent to" should be interpreted as well.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, the terms "comprises ", or" having ", or the like, specify that there is a stated feature, number, step, operation, , Steps, operations, components, parts, or combinations thereof, as a matter of principle.

Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries should be construed as meaning consistent with meaning in the context of the relevant art and are not to be construed as ideal or overly formal in meaning unless expressly defined herein .

2A and 2B are graphs showing the operation of an existing automatic emergency braking system using only the brake hydraulic pressure and the operation of the automatic emergency braking system according to an embodiment of the present invention. The horizontal axis of the graph means the time remaining until collision with the preceding vehicle. The vertical axis represents the size of each.

As shown in FIG. 2A, in the case of the conventional automatic emergency braking system, it can be seen that the pre-fill is started 1.8 seconds before the collision with the preceding vehicle even though the TTC is 1.5 seconds. That is, the pre-fill has the effect of substantially increasing the TTC to 1.8 seconds, which can cause the automatic emergency braking system to operate more and cause discomfort to the driver. On the other hand, referring to FIG. 2B according to an automatic emergency braking method according to an embodiment of the present invention, it can be seen that the pre-fill process disappears by applying the braking force of the motor from the moment when the TTC becomes 1.5 seconds. That is, the drive motor used in the EV and HEV can generate an immediate braking force, eliminating the pre-fill process from before the TTC, and braking due to the braking force of the drive motor when the TTC is established, Hydraulic pressure can be raised. That is, the braking force of the motor can replace the pre-fill process required when only the hydraulic brake is used.

3 is a flowchart illustrating an automatic emergency braking method according to an embodiment of the present invention.

The automatic emergency braking system according to an embodiment of the present invention may include a hydraulic brake, a drive motor, and a control unit. The hydraulic brake is a braking device that brakes using the existing hydraulic pressure, and the driving motor receives the power of the battery and generates and regenerates the driving force of the vehicle according to the traveling mode.

The control unit can control the entire system of the automatic emergency braking system, and can first determine whether braking is possible by using the driving motor (S301). If the braking using the drive motor is not possible, it is necessary to perform the braking only with the hydraulic pressure of the hydraulic brake as in the conventional method. In order to determine this, it is possible to determine whether the braking force of the motor is equal to or greater than a predetermined reference value by referring to the torque limit value of the motor and the charging limit value of the high voltage battery. The torque limit value of the drive motor and the charge limit value of the high voltage battery depend on the temperature of the components and the state of charge (SOC), so the automatic emergency braking system must be judged beforehand. That is, the available braking force of the drive motor can be calculated based on the torque limit value of the drive motor, and the charge limit value of the battery that powers the drive motor.

Next, the control unit may determine whether automatic emergency braking is necessary (S303). That is, whether the AEB is in the active state, it is possible to judge whether the preceding vehicle or the preceding vehicle satisfies the TTC. The braking can be automatically and urgently performed when the time of collision with a preceding vehicle or an object ahead is shorter than a preset time. That is, when the TTC is equal to or less than the preset time, the braking force of the driving motor can be utilized by transmitting a braking command to the driving motor.

If the AEB is active, it must be braked using a drive motor. At this time, the control unit issues a braking command to the driving motor, which is calculated by the control unit, and can be determined differently according to the relative vehicle speed between the preceding vehicle and the preceding vehicle and the TTC. For example, if the preceding vehicle is in a stopped state, the vehicle is in a running state at 10 kph, and the TTC is 1.5 seconds, it is necessary to decelerate the vehicle with a braking force of 10 kph / 1.5 sec. If the speed of the vehicle is 100kph, 10 times greater braking force may be required. That is, the control unit can calculate the required automatic braking force based on the time (TTC: time to collision) until collision with the preceding vehicle and the relative speed of the preceding vehicle and the preceding vehicle.

The control unit then compares the available braking force of the driving motor with the required automatic braking force and if the available braking force of the motor is larger than the required automatic braking force, the automatic braking of the vehicle can be performed using only the motor (S307 ).

Alternatively, if the available braking force of the driving motor is smaller than the required automatic braking force, the control unit may automatically brake the vehicle using the motor and the hydraulic brake at the same time (S309).

The control unit may then determine whether the braking of the motor is necessary to be released (S311). If the braking using the drive motor is impossible during the automatic braking using the drive motor, the hydraulic brakes can generate all the braking forces. Specifically, it is determined whether a failure or limitation of a PE (Power Electric) driven electric component such as a motor, an inverter, or a high voltage battery occurs, or whether a wheel lock occurs on a slippery road surface.

If the drive motor can not be braked due to a failure or limitation of the PE part, the hydraulic brake must be immediately raised to brake the hydraulic brake (S313). At this time, when the electric parts including the motor and the battery do not operate normally, the control unit can increase the braking force of the hydraulic brake by the reduced motor braking force. Thus, the total braking force can be controlled to be constant so that the driver can feel the linear braking feeling.

If the brake is disabled by using a drive motor due to wheel lock, etc., ABS or ESC control must be performed. In this case, ABS should be simulated with a drive motor to prevent wheel lock, or the motor braking force should be replaced with hydraulic braking force. That is, when a wheel lock occurs in the wheel of the vehicle, the braking torque of the drive motor can be adjusted to zero, or the braking force of the hydraulic brake can be increased by the reduced motor braking force.

When a wheel lock occurs, it is first determined whether there is a braking force by the hydraulic pressure. If there is no braking force by the hydraulic pressure, the motor braking force is made zero. If the wheel is unlocked, the motor braking force is generated again. At this time, the braking force is reduced by a predetermined amount, for example, 5% smaller than the previous motor braking force. This is to find the braking force that the maximum frictional force of the tire can withstand, gradually lowering the braking force. When a certain amount of braking force is applied, it is judged whether or not the wheel is unlocked. If the tire friction is moderately shrunk to such an extent that it can withstand, the wheel will remain unlocked and will be the maximum braking force. On the other hand, if the hydraulic pressure is present, the motor braking force is set to zero. At this time, since the hydraulic pressure acts as the braking force, the wheel may not be unlocked. If the wheel is unlocked, it means that the kinetic frictional force of the tire can withstand the braking force by the hydraulic pressure. Therefore, it is only necessary to find the maximum braking force by reducing the braking force of the motor. If the wheel is not unlocked, wait a certain amount of time. The predetermined time is the on / off period of the hydraulic cycle of the vehicle equipped with the ABS. The reason for waiting for this time is to judge whether the wheel lock can be controlled only by the motor or by setting the hydraulic lock to 0 so that the control is possible.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to the preferred embodiments of the present invention with reference to the accompanying drawings. Like reference symbols in the drawings denote like elements.

300: Automatic emergency braking method

Claims (9)

Calculating a required automatic braking braking force based on a time to collision (TTC) until collision with the preceding vehicle and a relative speed between the preceding vehicle and the preceding vehicle;
And automatically braking the vehicle by using only the motor in accordance with the available braking force of the motor and the required magnitude of the automatic braking force, or using the motor and the hydraulic brake at the same time,
Automatic emergency braking method. The method according to claim 1,
Further comprising the step of determining whether the available braking force of the motor is greater than a preset reference value before the automatic braking step,
Automatic emergency braking method. 3. The method of claim 2,
Wherein the available braking force of the motor is calculated based on a torque limit value of the motor and a charging limit value of a battery that powers the motor.
Automatic emergency braking method. The method according to claim 1,
And transmitting a braking command to the motor when the TTC is less than or equal to a predetermined time.
Automatic emergency braking method. The method according to claim 1,
Wherein the step of automatically braking the vehicle is a step of automatically braking the vehicle using only the motor when the available braking force of the motor is larger than the required automatic braking force.
Automatic emergency braking method. The method according to claim 1,
Wherein the step of automatically braking the vehicle is a step of automatically braking the vehicle using the motor and the hydraulic brake simultaneously when the available braking force of the motor is smaller than the required automatic braking force.
Automatic emergency braking method. The method according to claim 1,
Further comprising the step of increasing the braking force of the hydraulic brake by the reduced motor braking force when the electric component including the motor and the battery does not operate normally during the automatic braking using the motor,
Automatic emergency braking method. The method according to claim 1,
Further comprising the step of adjusting the braking torque of the motor to zero or increasing the braking force of the hydraulic brake when a wheel lock occurs in the wheel of the vehicle during automatic braking using the motor,
Automatic emergency braking method. Hydraulic brake;
A drive motor; And
Calculating a required automatic braking force based on a time to collision (TTC: time to collision) between the preceding vehicle and the preceding vehicle, and a relative speed between the preceding vehicle and the preceding vehicle, And a control unit that uses only the drive motor in accordance with the magnitude of the braking force or uses the drive motor and the hydraulic brake simultaneously to automatically brake the vehicle.
Automatic emergency braking system.

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