KR102587246B1 - Emergency braking method for autonomous vehicle of dangerous situation - Google Patents

Abstract

In the present invention, when the collision determination unit determines that there is a possibility of collision with a preceding vehicle located in front of the driving vehicle, a) the braking unit applies coordinated braking to the left and right or front and rear wheels of the driving vehicle, or the steering unit performs steering through steering. forming lateral acceleration; It includes, and the braking unit performs coordinated braking so that the lateral acceleration reaches the target lateral acceleration a _{y, tar,} which is set to a value within the lateral acceleration obtainable in the state of the road surface by reflecting the friction coefficient of the road surface on which the traveling vehicle is located. or provides an emergency braking method in a dangerous situation for an autonomous vehicle, wherein the steering unit performs steering.
According to the present invention, there is an advantage in that the collision avoidance performance of an autonomous vehicle can be improved by simultaneously performing steering or coordinated braking.
In addition, when collision avoidance is not possible through steering or coordinated braking, there is an advantage in maximizing the collision avoidance performance of the autonomous vehicle by losing the lateral force of the rear wheels.

Description

Emergency braking method for self-driving vehicles in dangerous situations {EMERGENCY BRAKING METHOD FOR AUTONOMOUS VEHICLE OF DANGEROUS SITUATION}

The present invention relates to an emergency braking method in a dangerous situation for an autonomous vehicle to prevent a collision when it is determined that there is a possibility of collision between a running autonomous vehicle and a preceding vehicle, especially when collision avoidance through steering or coordinated braking is not possible. This relates to an emergency braking method in a dangerous situation for an autonomous vehicle that performs emergency braking by losing the lateral force of the rear wheels.

A self-driving car is a car that understands the road situation and drives automatically without the driver having to control the brakes, steering wheel, or accelerator pedal. It recognizes the driving environment, creates a driving path, and recognizes obstacles or preceding vehicles to detect obstacles or preceding vehicles. Devices and algorithms are being developed to avoid collisions.

Change the driving path of the self-driving car or apply braking to avoid collision with obstacles or preceding vehicles.

In this regard, the existing Korean Patent Publication No. 10-2018-0032044 (Autonomous vehicle that enhances steering performance by applying biased braking force in emergency situations) is an autonomous vehicle that enhances steering performance by applying biased braking force in emergency situations. Regarding this, the target direction of progress is set, and in order to secure additional steering force by activating the emergency steering control function when the target direction cannot be followed with steering force alone, a biased braking force is applied to the wheel on the side of the target direction to provide additional steering force. Self-driving cars that generate are being launched.

However, the conventional technology had a problem in that the braking force was limited to assisting steering and the braking force could not be sufficiently applied to avoid collision with the preceding vehicle.

In addition, there is no alternative in case a collision with a preceding vehicle cannot be avoided through steering or coordinated braking alone in an emergency situation, so there is a problem that it cannot be used in an actual emergency situation.

Korean Patent Publication No. 10-2018-0032044

In the existing emergency braking method for autonomous vehicles, the present invention provides steering or uniform braking of the autonomous vehicle in a dangerous situation where the possibility of collision with the preceding vehicle is judged, and when collision avoidance through steering or single braking is not possible, the rear wheel The purpose is to provide sufficient braking force to avoid collision between the driving vehicle and the preceding vehicle by losing the lateral force of the vehicle.

In order to achieve the above object, the present invention provides that, when the collision determination unit determines that there is a possibility of collision with a preceding vehicle located in front of the traveling vehicle, a) the braking unit performs coordinated braking on the left and right or front and rear wheels of the traveling vehicle, or Or, the steering unit forms lateral acceleration through steering; It includes, and the braking unit performs coordinated braking so that the lateral acceleration reaches the target lateral acceleration a _{y, tar,} which is set to a value within the lateral acceleration obtainable in the state of the road surface by reflecting the friction coefficient of the road surface on which the traveling vehicle is located. or provides an emergency braking method in a dangerous situation for an autonomous vehicle, wherein the steering unit performs steering.

Preferably, the control unit determines whether collision avoidance is possible through step a), and if collision avoidance is determined to be impossible, b) the braking unit performs emergency braking to lose the lateral force of the rear wheels of the driving vehicle. can do.

Preferably, step a) includes setting the a _{y, tar} value to a value within the lateral acceleration that can be obtained from the state of the road surface by the setting unit reflecting the friction coefficient; The calculation unit determines the target deviation angle based on the distance between the driving vehicle and the preceding vehicle. Calculating the required steering angle δ _req or the required steering power F _req proportional to a _{y, tar} ; and forming lateral acceleration by the steering unit performing steering or the braking unit performing coordinated braking according to the calculated δ _req or F _req .

Preferably, the step of forming lateral acceleration includes a first step in which the control unit inputs δ _req or F _req to the steering unit or the braking unit; A second step in which the sensor unit senses the lateral acceleration and departure angle of the driving vehicle generated according to the input δ _req or F _req ; The control unit determines whether the lateral acceleration has reached a _{y, tar} and the departure angle is *gain The third step is to determine whether it has been reached; And the control unit determines that the lateral acceleration reaches a _{y, tar} and the departure angle *gain (gain ; A fourth step of inputting δ _req or F _req to the steering unit or braking unit until a constant less than 1) is reached may be further included.

Preferably, the control unit is a _y,sensed < a _y,tar and < *gain (a _y,sensed ; lateral acceleration measured by the sensor unit, ; Steps 1 to 4 are repeatedly performed while the condition of the departure angle measured by the sensor unit is satisfied, and it may be characterized in that it is determined that collision avoidance through steering or coordinated braking is impossible under other conditions. .

Preferably, step b) includes a step in which the calculation unit calculates a longitudinal force _F It may further include causing the control unit to apply a braking force greater than _F

Preferably, the step of losing the lateral force of the rear wheels includes: having the sensor unit sense the departure angle of the driving vehicle; The calculation unit determines the target departure angle based on the distance between the driving vehicle and the preceding vehicle. A step of calculating; And the departure angle of the control unit is It may further include applying a braking force greater than F _x to the rear wheel until .

According to the present invention having the above-described configuration, there is an advantage in that the collision avoidance performance of an autonomous vehicle can be improved by simultaneously performing steering or coordinated braking.

In addition, the present invention has the advantage of being able to vary the avoidance method depending on whether the lateral acceleration and departure angle required for collision avoidance have been reached by feeding back the lateral acceleration and departure angle of the autonomous vehicle sensed using a sensor through the control unit. There is.

Additionally, the present invention has the advantage of maximizing the collision avoidance performance of an autonomous vehicle by losing the lateral force of the rear wheels when collision avoidance is impossible through steering or coordinated braking.

Figure 1 shows an emergency braking system in a dangerous situation for an autonomous vehicle according to the present invention.
Figure 2 shows an emergency braking method in a dangerous situation of an autonomous vehicle according to an embodiment of the present invention.
Figure 3 shows a driving autonomous vehicle and a preceding vehicle.
Figure 4 shows the steps of forming lateral acceleration according to an embodiment of the present invention.
Figure 5 shows the behavior during coordinated braking or steering of the vehicle according to the present invention.
Figure 6 shows a collision avoidance determination step through forming lateral acceleration according to an embodiment of the present invention.
Figure 7 shows a rear wheel lateral force loss stage according to an embodiment of the present invention.
Figure 8 shows a collision avoidance determination step through loss of rear wheel lateral force according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited or limited by the exemplary embodiments. The same reference numerals in each drawing indicate members that perform substantially the same function.

The purpose and effect of the present invention can be naturally understood or become clearer through the following description, and the purpose and effect of the present invention are not limited to the following description. Additionally, in describing the present invention, if it is determined that a detailed description of known techniques related to the present invention may unnecessarily obscure the gist of the present invention, the detailed description will be omitted.

Figure 1 shows an emergency braking system 100 in a dangerous situation of an autonomous vehicle according to the present invention.

Referring to FIG. 1, the emergency braking system 100 in a dangerous situation of an autonomous vehicle of the present invention includes a collision determination unit 40, a setting unit 50, a calculation unit 60, a sensor unit 70, and a control unit 30. ), a braking unit 10, or a steering unit 20.

In a dangerous situation of an autonomous vehicle, the emergency braking system 100 includes a control unit 30 that receives information from the collision determination unit 40, setting unit 50, calculation unit 60, or sensor unit 70, and the braking unit ( 10) Alternatively, the steering unit 20 is controlled to perform emergency braking in a dangerous situation of the autonomous vehicle.

The collision determination unit 40 is a means for determining whether there is a possibility of a vehicle colliding with a preceding vehicle or an obstacle. The method of determining the possibility of collision in the collision determination unit 40 may be a known algorithm.

In the present invention, collision avoidance is performed through emergency braking after the possibility of collision is determined by the collision determination unit 40, and therefore, a detailed description of the collision determination unit 40 is omitted in the present invention.

The setting unit 50 may set a reference value including the target lateral acceleration a _{y, tar} in advance for emergency braking in a dangerous situation of the self-driving vehicle of the present invention.

The sensor unit 70 may sense driving environment information of the vehicle using image information, laser sensing information, radar reception information, etc. using devices such as cameras, laser scanners, and radars. The sensor unit 70 may include a wheel speed sensor, a brake sensor, and a steering angle sensor, but is not limited to this and may include any sensor that can detect the surrounding environment of the vehicle.

The calculation unit 60 determines the collision risk situation of the autonomous vehicle based on the vehicle speed of the driving vehicle, the vehicle speed of the preceding vehicle, the departure angle of the driving vehicle, and the friction coefficient of the road surface on which the driving vehicle is located, as recognized by the sensor unit 70. By executing a series of calculation processes for, it is possible to derive the result for emergency braking in a collision risk situation of an autonomous vehicle.

The control unit 30 allows the braking unit 10 and the steering unit 20 to input braking force, steering angle, and braking time for emergency braking, and may be composed of a control unit such as an ECU (Electric Control Unit). .

The braking unit 10 automatically applies integrated braking to the left and right or front and rear wheels to generate positive acceleration of the vehicle, or uses ABS (Anti-lock Braking System) and ESC to apply braking to lose the lateral force of the rear wheels. It may consist of a braking device such as (Electronic Stability Control) or AEB (Advanced Emergency Brake).

The steering unit 20 may be configured as a Motor Driven Power Steering system (MDPS) to automatically perform steering to generate lateral acceleration.

Information transmission and reception between the sensor unit 70, calculation unit 60, setting unit 50, or collision determination unit 40 and the control unit 30 may use a communication method such as CAN (Controller Area Network) communication, and the control unit The method of transmitting and receiving information between 30 and the braking unit 10 or steering unit 20 is also the same.

Figure 2 shows an emergency braking method in a dangerous situation of an autonomous vehicle according to an embodiment of the present invention.

Referring to FIG. 2, when the collision determination unit 40 determines the possibility of a collision between the driving vehicle and the preceding vehicle located in front of the driving vehicle (S10), the braking unit 10 is applied to the left and right or front and rear wheels of the driving vehicle. Coordinated braking may be performed or the steering unit 20 may generate lateral acceleration through steering (S20).

When the control unit 30 determines that collision avoidance is possible by forming lateral acceleration, the control unit 30 causes the braking unit 10 or the steering unit 20 to determine the lateral acceleration and departure angle of the traveling vehicle under certain conditions described later. The lateral acceleration can be formed repeatedly (S20) until this is satisfied.

Although not shown in the drawing, when lateral acceleration is formed and avoidance of the preceding vehicle is completed and the possibility of collision is eliminated, a process of returning to driving after executing the lateral acceleration forming step may be further included.

If the control unit 30 determines that collision avoidance is impossible by creating lateral acceleration, the control unit 30 causes the braking unit 10 to perform emergency braking to lose the lateral force of the rear wheels of the vehicle (S40). can do.

The control unit 30 may cause the braking unit 10 to repeatedly cause the lateral force of the rear wheels to be lost (S40) until the departure angle of the traveling vehicle satisfies a certain condition (S50), which will be described later.

Although not shown in the drawing, when avoiding the preceding vehicle is completed through the step of losing the lateral force of the rear wheels (S40) and the possibility of collision is eliminated, the process of losing the lateral force of the rear wheels (S40) and then returning to driving is further performed. It can be included.

Figure 3 shows a driving autonomous vehicle and a preceding vehicle.

Referring to FIG. 3, the driving information of the vehicle measured by the sensor unit 70 can be known. V is the speed of the driving vehicle, V _F is the speed of the preceding vehicle, W is the road width, W' is the width of the preceding vehicle, and ΔS is the distance between the driving vehicle and the preceding vehicle.

Figure 4 shows the lateral acceleration formation (S20) step according to an embodiment of the present invention.

Referring to FIG. 4, the lateral acceleration formation (S20) step includes the setting unit 50 setting the a _y,tar value to a value within the lateral acceleration that can be obtained from the state of the road surface by reflecting the friction coefficient (S210); The calculation unit 60 sets the target deviation angle based on the distance between the driving vehicle and the preceding vehicle. Calculating the required steering angle δ _req or the required steering power F _req proportional to a _{y, tar} (S230); and a step (S250) in which the steering unit 20 performs steering or the braking unit 10 performs coordinated braking according to the calculated δ _req or F _req to form lateral acceleration.

First, the setting unit 50 reflects the friction coefficient μ of the road surface on which the driving vehicle is located and sets the target lateral acceleration a _{y,tar value as a value within μ*g (g is the gravitational acceleration),} which is the lateral acceleration value that can be obtained from the state of the road surface. can be set.

μ can use a value directly measured by the sensor unit 70, and the sensor unit 70 measures road surface conditions such as temperature or humidity of the road surface and sets a value previously set in the setting unit 50 according to the road surface conditions. You can also use it.

After setting the target value of lateral acceleration _{, ay,tar,} in the setting unit 50, the calculation unit 60 sets the target deviation angle based on the distance between the driving vehicle and the preceding vehicle measured by the sensor unit 70. You can calculate the required steering angle δ _req or the required steering power F _req proportional to a _{y, tar} .

In order to calculate δ _req, first, the required yaw rate γ _req required to avoid the preceding vehicle through coordinated braking or steering must be calculated using the set a _y,tar , and this can be calculated through the Eckerman yaw rate.

Yaw rate, also known as yaw angle speed, refers to the speed at which the rotation angle (yaw angle) changes around a vertical line passing through the center of the car. Ackermann yaw rate uses a linear tire model to express the relationship between a vehicle's yaw rate and steering angle.

The Ackerman yaw rate can be calculated with reference to FIG. 5, which shows the behavior during coordinated braking or steering of a driving vehicle.

5, γ is the yaw rate of the driving vehicle, F _sf is the lateral force of the front wheels, F _sr is the lateral force of the rear wheels, α _f is the slip angle of the front wheels, α _r is the slip angle of the rear wheels, C _f is the cornering stiffness of the front wheels, C _r is the cornering stiffness of the rear wheels, l _f is the distance from the center of gravity of the vehicle to the front wheels, l _r is the distance from the center of gravity of the vehicle to the rear wheels, m is the weight of the vehicle, δ is the steering angle, and R is the cornering radius. means.

γ _req can be calculated with the following equation.

Additionally, F _sf and F _sr can be calculated using the following equation.

At this time, α _f and α _r can be calculated using the following equation.

( )

( )

In addition, R is calculated as follows, and the relationship between γ and R can be derived as follows.

At this time, if γ is the required yaw rate γ _req required to avoid the preceding vehicle, γ _req can be calculated as follows.

,

At this time, the departure angle can be calculated using the formula below.

At this time, ,

The above δ can be set as the required steering angle δ _req required for the driving vehicle to avoid collision with the preceding vehicle.

F _req can be calculated with the following equation.

At this time, N refers to the vertical force acting on the wheel, μ is the friction coefficient, g refers to the gravitational acceleration, and gain _brk is the gain value for calculating the control amount. Depending on the vehicle type, it is a value for tuning and is determined through experiment or sensor It may be a value sensed by unit 70.

In the above-described process, values that cannot be obtained through calculation can be sensed by the sensor unit 70 or calculated through values sensed by the sensor unit 70.

When δ _req or F _req is calculated, the control unit 30 causes the steering unit 20 to steer based on this or the braking unit 10 to perform coordinated braking to avoid a collision with the preceding vehicle. Lateral acceleration can be formed for

Figure 6 shows a collision avoidance determination step (S250) by forming lateral acceleration according to an embodiment of the present invention.

Referring to FIG. 6, the collision avoidance determination step (S250) through yellow acceleration formation is the first step (S251) in which the control unit 30 inputs δ _req or F _req to the steering unit 20 or the braking unit 10. ; A second step (S253) in which the sensor unit 70 senses the lateral acceleration and departure angle of the traveling vehicle generated according to the input δ _req or F _req ; The control unit 30 determines whether the lateral acceleration has reached a _{y, tar} and the departure angle is *gain (gain ; A third step (S255) to determine whether a constant less than 1 has been reached; And the control unit 30 determines that the lateral acceleration reaches a _{y, tar} and the departure angle *gain It may further include a fourth step (S257) of inputting δreq or Freq to the steering unit 20 or the braking unit 10 until .

The control unit 30 is a _{y, sensed} < a _{y, tar} and < *gain (a _{y, sensed} ; lateral acceleration measured by the sensor unit 70, ; Steps 1 to 4 may be repeatedly performed while the condition of the departure angle measured by the sensor unit 70 is satisfied, and it may be determined that collision avoidance through steering or coordinated braking is impossible under other conditions.

The sensed lateral acceleration is smaller than the target lateral acceleration a _y,tar, which is the maximum lateral acceleration that can be obtained under the current road surface conditions, and is set smaller than the target departure angle. *gain If the sensed departure angle is smaller than the value, the driving vehicle must still generate lateral acceleration to avoid collision with the preceding vehicle, and steps 1 to 4 may be repeatedly performed.

can be calculated with the formula below.

Target departure angle required for a driving vehicle to avoid collision with a preceding vehicle It can be set as a value.

At this time, The value can be obtained as the arc tangent value of the distance ΔS between the driving vehicle and the preceding vehicle compared to the vehicle width W' of the preceding vehicle. However, the arc tangent result value can be adjusted to be high. The value can be set larger than the departure angle required to actually avoid a collision. This is to ensure safety by setting the target departure angle necessary for collision avoidance with more margin than the actual required departure angle.

gain The value is a gain setting value for performance tuning freedom when configuring the control logic. It is a value set according to trial-and-error or the engineer's know-how. It is set to a value less than 1, which is smaller than the actual target deviation angle. *gain Even if the departure angle equal to the value is sensed, stability can be ensured by implementing the rear wheel lateral force loss stage.

The control unit 30 is a _{y, sensed} < a _{y, tar} or < *gain Even if only one of the conditions is not satisfied, the rear wheel lateral force loss stage can be performed.

Figure 7 shows a rear wheel lateral force loss step (S40) according to an embodiment of the present invention.

Referring to FIG. 7, in the rear wheel lateral force loss step (S40), the calculation unit 60 calculates the longitudinal force F applied to the rear wheel as the product of the friction coefficient of the road surface on which the traveling vehicle is located and the vertical force acting on the rear wheel of the traveling vehicle. Step of calculating _x (S410); It may further include a step (S430) of causing the control unit 30 to apply a braking force greater than _F

Figure 8 shows a collision avoidance determination step through loss of rear wheel lateral force according to an embodiment of the present invention.

Referring to FIG. 8, the step of losing the lateral force of the rear wheels (S430) includes the step of the sensor unit 70 sensing the departure angle of the driving vehicle (S431); The calculation unit 60 sets the target deviation angle based on the distance between the driving vehicle and the preceding vehicle. A step of calculating (S433); and the control unit 30 has a departure angle It may further include applying a braking force greater than F _x to the rear wheel until it reaches (S435).

Sensed departure angle go When , the rear wheel lateral force loss stage can be ended.

Although the present invention has been described in detail through representative embodiments above, those skilled in the art will understand that various modifications can be made to the above-described embodiments without departing from the scope of the present invention. will be. Therefore, the scope of rights of the present invention should not be limited to the described embodiments, but should be determined not only by the patent claims described later, but also by all changes or modified forms derived from the claims and the concept of equivalents.

100: Emergency braking system in dangerous situations of autonomous vehicles
10: Braking unit
20: steering unit
30: control unit
40: Collision determination unit
50: Setting section
60: calculation unit
70: sensor unit

Claims (7)

If the collision determination unit determines that there is a possibility of collision with a preceding vehicle located in front of the driving vehicle,
a) a step of the braking unit performing coordinated braking on the left and right or front and rear wheels of the driving vehicle, or the steering unit forming lateral acceleration through steering;
The braking unit performs coordinated braking so that the lateral acceleration reaches the target lateral acceleration a _y,tar, which is set to a value within the lateral acceleration obtainable from the state of the road surface by reflecting the friction coefficient of the road surface on which the traveling vehicle is located, or The steering unit performs steering,
In step a),
A setting unit setting a _y,tar value to a value within the lateral acceleration obtainable from the state of the road surface by reflecting the friction coefficient;
The calculation unit determines the target deviation angle based on the distance between the driving vehicle and the preceding vehicle. Calculating a required steering angle δ _req and a required steering power F _req proportional to a _{y, tar} ; and
An emergency braking method in a dangerous situation for an autonomous vehicle comprising: forming lateral acceleration by the steering unit performing steering or the braking unit performing coordinated braking according to the calculated δ _req or F _req .
The method of claim 1, wherein when the control unit determines whether collision avoidance is possible through step a) and determines that collision avoidance is impossible,
b) performing emergency braking to cause the braking unit to lose lateral force of the rear wheels of the driving vehicle; emergency braking method in a dangerous situation for an autonomous vehicle, further comprising:
delete The method of claim 1, wherein forming the lateral acceleration comprises:
A first step in which the control unit inputs the δ _req or the F _req to the steering unit or the braking unit;
A second step in which the sensor unit senses the lateral acceleration and departure angle of the traveling vehicle generated according to the input δ _req or F _req ;
The control unit determines whether the lateral acceleration has reached the a _{y, tar} and the departure angle is *gain The third step is to determine whether it has been reached; and
The control unit determines that the lateral acceleration reaches the a _{y, tar} and the departure angle is set to the *gain A fourth step of inputting the δ _req or the F _req to the steering unit or the braking unit until reaching .
(gain ; constant less than 1)
The method of claim 4, wherein the control unit a _{y, sensed} < a _{y, tar} < *gain Emergency braking in a dangerous situation for an autonomous vehicle, characterized in that the first to fourth steps are repeatedly performed while the conditions of are satisfied, and collision avoidance through steering or coordinated braking is determined to be impossible under other conditions. method.
(a _y,sensed ; lateral acceleration measured by the sensor unit, ; deviation angle measured by the sensor unit)
The method of claim 2, wherein step b) is:
A calculation unit calculating a longitudinal force _F and
An emergency braking method in a dangerous situation of an autonomous vehicle further comprising: causing the control unit to apply a braking force greater than _F
The method of claim 6, wherein the step of losing the lateral force of the rear wheel is:
A sensor unit sensing a departure angle of the driving vehicle;
The calculation unit determines the target departure angle based on the distance between the driving vehicle and the preceding vehicle. A step of calculating; and
The control unit determines the departure angle Applying a braking force greater than Fx to the rear wheels until reaching . Emergency braking method in a dangerous situation for an autonomous vehicle further comprising.