CN111169462A - Safe distance calculation module and calculation method thereof - Google Patents

Abstract

The invention discloses a safe distance calculation module for AEB and/or FCW, comprising: the data acquisition unit is used for acquiring the relative distance between the self vehicle and the target vehicle, the speeds of the self vehicle and the target vehicle, the accelerations of the self vehicle and the target vehicle and the braking reaction time; a most dangerous moment calculation unit for determining a most dangerous moment; and the minimum emergency braking distance calculating unit is used for calculating the minimum emergency braking distance according to the sequence of the stop of the vehicle and the stop of the target vehicle and whether the time required by the stop of the target vehicle and the stop of the vehicle is within the braking reaction time. The invention also discloses a safe distance calculation method for calculating the early warning safe distance for the automatic emergency braking of the vehicle and/or the front collision of the vehicle. According to the invention, the minimum distance that the vehicle is not collided during emergency braking is calculated by analyzing the sequence of the self vehicle and the target vehicle and the number and positions of the constant speed points, the minimum distance can be used for reducing the false alarm rate of FCW and the false touch rate of AEB, and the competitiveness of the enhanced product can be improved.

Description

Safe distance calculation module and calculation method thereof

Technical Field

The invention relates to the field of automobiles, in particular to a safe distance calculation module for an automatic emergency braking system and/or a front collision early warning system of a vehicle. The invention also relates to a safe distance calculation method for the automatic emergency braking of the vehicle and/or the early warning of the front collision of the vehicle.

Background

A vehicle front collision warning system (FCW) can monitor a vehicle ahead at any time through a radar system, determine the distance, direction, and relative speed between the vehicle and the vehicle ahead, and warn the driver when there is a potential collision hazard. The FCW system itself does not take any braking action to avoid a collision or to control the vehicle.

The automatic emergency braking system (AEB) of the vehicle measures the distance between the vehicle and a front vehicle or an obstacle by adopting a radar, then compares the measured distance with an alarm distance and a safety distance by utilizing a data analysis module, carries out alarm prompt when the measured distance is less than the alarm distance, and even if a driver does not have time to step on a brake pedal when the measured distance is less than the safety distance, the AEB system can be started to automatically brake the vehicle, so that the safe trip driving is protected.

The safety distance of the automatic emergency braking system and the front collision early warning system of the vehicle is a key parameter for realizing the control scheme. The emergency braking distance is the reaction distance + the braking distance. The current FCW/AEB safety distance has the following problems:

1) simplifying the motion of the vehicle and the target in the system delay and driver reaction stages into uniform motion;

2) the safety distance during braking is based on the distance required from the braking of the vehicle to the stop as the braking safety distance, and only the displacement, the speed and the acceleration of the vehicle are considered, and the displacement, the speed and the acceleration of the target are not considered. The oversimplified model has large deviation from the actual, and the calculated safe distance is not accurate.

In the prior art, the consideration factors are incomplete, the model is over simplified, and the relative distance, the speed and the acceleration of a vehicle and a target cannot be comprehensively considered, so that the FCW false alarm rate is high, and the emergency brake is easily triggered by mistake. When the AEB is triggered, the vehicle is braked at the maximum deceleration, the impact feeling is strong, the driving experience of people is poor, and the current AEB has the condition of false triggering, which is caused by conservative calculated safety distance.

Disclosure of Invention

In this summary, a series of simplified form concepts are introduced that are simplifications of the prior art in this field, which will be described in further detail in the detailed description. This summary of the invention is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

The invention aims to provide a safe distance calculation module which can accurately calculate the safe distance of an automatic emergency braking system and/or a front collision early warning system of a vehicle according to the relative position, speed, acceleration and motion state of a vehicle and a target vehicle.

The invention aims to solve another technical problem of providing a safe distance calculation method which can accurately calculate the safe distance for the automatic emergency braking and/or the front collision early warning of the vehicle according to the relative position, speed, acceleration and motion state of the vehicle and the target vehicle.

In order to solve the above technical problems, the present invention provides a safe distance calculating module for an automatic emergency braking system and/or a vehicle front collision warning system, comprising:

the system comprises a data acquisition unit, a data processing unit and a control unit, wherein the data acquisition unit is suitable for acquiring the relative distance between a self vehicle and a target vehicle, the speed of the self vehicle, the speed of the target vehicle, the acceleration of the self vehicle, the acceleration of the target vehicle and the braking reaction time;

optionally, the data acquisition unit comprises a wheel pulse sensor, a millimeter wave radar and an acceleration sensor. The wheel pulse sensor is used for obtaining the wheel speed, and the vehicle speed V can be obtained through kinematic analysis; the millimeter wave radar obtains the relative distance d between the vehicle and the target vehicle_rRelative velocity V_rRelative acceleration a_rInformation; acceleration sensor for obtaining acceleration a of vehicle_s. And further can be obtained by calculation, the target vehicle speed V_tTarget vehicle acceleration a_t。

A most dangerous moment calculation unit adapted to determine a most dangerous moment based on the own vehicle speed, the own vehicle stop required time, the target vehicle speed, the target vehicle stop required time, the own vehicle acceleration, and the target vehicle acceleration;

and the minimum emergency braking distance calculation unit is used for calculating the difference value of the running distance of the self vehicle from the target vehicle at the most dangerous moment according to the sequence of the self vehicle stopping and the target vehicle stopping and whether the time required by the target vehicle stopping and the time required by the self vehicle stopping are within the braking reaction time, wherein the distance difference value is the minimum emergency braking distance.

Optionally, the safety distance calculation module is further improved, and the brake reaction time comprises data acquisition time, data analysis time, emergency brake decision making time, brake clearance elimination time and brake force increasing time from zero to maximum.

Optionally, the safe distance calculation module is further improved, and the calculation mode of the time required by the vehicle to stop is as follows; (V)_s+a_sWhen x T) > 0, the time required for stopping the bicycle is

(V_s+a_sX T) is less than or equal to 0, the time required for stopping the bicycle is

T is the brake reaction time, V_sIs the speed of the bicycle, a_sIs the acceleration of the bicycle, a_minIs the maximum deceleration produced by wheel braking, in units: m/s²。

4. A safe distance calculation module as defined in claim 3, wherein: the target vehicle stop required time is calculated as follows;

a_tif > 0, then t_ts＝∞；

a_t0 and V_tNot equal to 0, then t_ts＝∞；

a_t0 and V_tWhen t is equal to 0_ts＝0；

a_tIf less than 0, then

a_tIs the target vehicle acceleration, V_tIs the target vehicle speed, t_tsIs the time required for the target vehicle to stop.

Optionally, the safety distance calculation module is further improved, and when the front target vehicle stops first, and then stops, the vehicle stops at the most dangerous moment.

Optionally, the safety distance calculation module is further modified, if there is no constant speed moment in both the braking response time and the braking response time of the target vehicle and the host vehicle, the speed of the host vehicle is always lower than the speed of the target vehicle, and the safety distance d required for safety is kept equal to 0.

Optionally, the safe distance calculation module is further improved, the front target vehicle stops at the rear, t_ss＜t_tsAnd the bicycle stops T within the time T first_ss＜T；

If the target vehicle and the host vehicle only have one constant speed moment, and the constant speed moment is within the braking reaction time, the constant speed moment is the most dangerous moment;

t is the brake reaction time, T_ssIs the time required for the vehicle to stop, t_tsIs the time required for the target vehicle to stop.

Optionally, the safe distance calculation module is further improved, and the front target vehicle stops at the rear t_ss＜t_tsAnd the bicycle stops t before the braking reaction time_ss＞T；

If the target vehicle and the host vehicle only have one constant speed moment, and the constant speed moment is out of the braking reaction time, the constant speed moment is the most dangerous moment;

if the target vehicle and the self vehicle have two constant speed moments which are out of the braking reaction time, the second coming constant speed moment is the most dangerous moment;

t is the brake reaction time, T_ssIs the time required for the vehicle to stop, t_tsIs the time required for the target vehicle to stop.

Optionally, the safety distance calculation module is further improved, when the front target vehicle stops first, stops after the vehicle stops, and t_ts＜t_ssWhen < T, the required safety distance is

d＝(0-V_s ²)/(2*a_s)-(0-V_t ²)/(2*a_t)；

T is the brake reaction time, V_sIs the speed of the bicycle, V_tIs the target vehicle speed, a_sIs the acceleration of the bicycle, a_tIs the target vehicle acceleration, t_ssIs the time required for the vehicle to stop, t_tsIs the time required for the target vehicle to stop.

Optionally, the safety distance calculation module is further improved, when the front target vehicle stops first, stops after the vehicle stops, and t_ts＜t_ssAt > T, the required safety distance is

d＝V_s*T+1/2*a_s*T²+(0-(V_s+a_s*T)²)/(2*a_min)-(0-V_t ²)/(2*a_t)；

T is the brake reaction time, d is the required safety distance, V_sIs the speed of the bicycle, V_tIs the target vehicle speed, a_sIs the acceleration of the bicycle, a_tIs the target vehicle acceleration, t_ssIs the time required for the vehicle to stop, t_tsIs an objectTime required for vehicle stop, a_minIs the maximum deceleration produced by wheel braking, in units: m/s²。

Optionally, the safety distance calculation module is further improved if t e (0, t)_ss) The required safety distance is d ═ V_s-V_t)*t+1/2*(a_s-a_t)*t²；

d is the desired safety distance, V_sIs the speed of the bicycle, V_tIs the target vehicle speed, a_sIs the acceleration of the bicycle, a_tIs the target vehicle acceleration, and t is the time required for both vehicles to reach a constant speed.

Optionally, the safety distance calculation module is further modified if t_ts＜t_ssIf there is only one constant speed moment, the safety distance is

d＝V_s*T+1/2*a_s*T2+(V_s+a_s*T)*t_x+1/2*a_min*t_x ²-(V_t*(T+t_x)+1/2*a_t*(T+t_x)²) ；

T is the brake reaction time, d is the required safety distance, V_sIs the speed of the bicycle, V_tIs the target vehicle speed, a_sIs the acceleration of the bicycle, a_tIs the target vehicle acceleration, t_xIs the time required for the two vehicles to reach a constant speed after T, a_minIs the maximum deceleration produced by wheel braking, in units: m/s²。

Optionally, the safety distance calculation module is further improved, and the safety distance required at the second constant speed moment is

d is the desired safety distance, V_sIs the speed of the bicycle, a_sIs the acceleration of the bicycle, a_tIs the target vehicle acceleration, V_tIs the target vehicle speed, t_yIs the time required for the second time of the last two cars to reach the constant speed, a_minIs the maximum deceleration, in units, produced by wheel braking：m/s²。

Optionally, the safety distance calculation module is further modified, if the target vehicle and the self vehicle travel at the same speed and the same speed, the required safety distance is d-V_sT, T is the brake reaction time, V_sIs the speed of the vehicle.

Optionally, the safety distance calculation module is further improved, if a_t＝0，V_tIf Vs is 0 in the braking reaction time of the bicycle, the required safety distance is d (0-V)_s ²)/(2*a_s)；

If Vs is more than 0 in the braking reaction time of the self-vehicle, the required safety distance is d-V_s*T+1/2*a_s*T²+(0-(V_s+a_s*T)²)/(2*a_min)；

T is the brake reaction time, d is the required safety distance, V_sIs the speed of the bicycle, a_sIs the acceleration of the bicycle, a_tIs the target vehicle acceleration, V_tIs the target vehicle speed, a_minIs the maximum deceleration produced by wheel braking, in units: m/s²。

The invention provides a safe distance calculation method for calculating the automatic emergency braking safe distance of a vehicle and/or the early warning safe distance of collision in front of the vehicle, which comprises the following steps:

s1, acquiring the relative distance between the vehicle and the target vehicle, the vehicle speed, the target vehicle speed, the vehicle acceleration, the target vehicle acceleration and the brake reaction time;

s2, determining the most dangerous moment according to the speed of the vehicle, the time required for stopping the vehicle, the speed of the target vehicle, the time required for stopping the target vehicle, the acceleration of the vehicle and the acceleration of the target vehicle;

and S3, calculating the difference value of the running distance of the vehicle from the target vehicle at the most dangerous moment according to the sequence of the stop of the vehicle and the stop of the target vehicle and whether the time required by the stop of the target vehicle and the time required by the stop of the vehicle are within the braking reaction time, wherein the distance difference value is the minimum emergency braking distance.

Optionally, the safety distance calculation method is further improved, and in step S3, the braking response time includes data acquisition time, data analysis time, emergency braking decision making time, brake clearance elimination time, and brake force increasing time from zero to maximum.

Optionally, the method for calculating the safe distance is further improved, in step S2, the calculation method of the time required for stopping the vehicle is as follows;

(V_s+a_swhen x T) > 0, the time required for stopping the bicycle is

(V_s+a_sX T) is less than or equal to 0, the time required for stopping the bicycle is

T is the brake reaction time, V_sIs the speed of the bicycle, a_sIs the acceleration of the bicycle, a_minIs the maximum deceleration produced by wheel braking, in units: m/s²。

Optionally, the safe distance calculation method is further improved, and the calculation mode of the time required by the target vehicle to stop is as follows;

a_tif > 0, then t_ts＝∞；

a_t0 and V_tNot equal to 0, then t_ts＝∞；

a_t0 and V_tWhen t is equal to 0_ts＝0；

a_tIf less than 0, then

a_tIs the target vehicle acceleration, V_tIs the target vehicle speed, t_tsIs the time required for the target vehicle to stop.

Optionally, the safe distance calculation method is further improved, and when the front target vehicle stops first, and then stops, the vehicle stops at the most dangerous moment.

Optionally, the safe distance calculation method is further improved, if the target vehicle and the host vehicle do not have the constant speed time no matter within the braking reaction time or outside the braking reaction time, the speed of the host vehicle is always lower than the speed of the target vehicle, and the safe distance d required for keeping the safety is 0.

Optionally, the safe distance calculation method is further improved, wherein the front target vehicle stops after stopping, t_ss＜t_tsAnd the bicycle stops T within the time T first_ss＜T；

If the target vehicle and the host vehicle only have one constant speed moment, and the constant speed moment is within the braking reaction time, the constant speed moment is the most dangerous moment;

t is the brake reaction time, T_ssIs the time required for the vehicle to stop, t_tsIs the time required for the target vehicle to stop.

Optionally, the safe distance calculation method is further improved, and the front target vehicle stops at the rear t_ss＜t_tsAnd the bicycle stops t before the braking reaction time_ss＞T；

If the target vehicle and the host vehicle only have one constant speed moment, and the constant speed moment is out of the braking reaction time, the constant speed moment is the most dangerous moment;

if the target vehicle and the self vehicle have two constant speed moments which are out of the braking reaction time, the second coming constant speed moment is the most dangerous moment;

t is the brake reaction time, T_ssIs the time required for the vehicle to stop, t_tsIs the time required for the target vehicle to stop.

Optionally, the safe distance calculation method is further improved, when the front target vehicle stops first, stops after the vehicle stops, and t_ts＜t_ssWhen < T, the required safety distance is

d＝(0-V_s ²)/(2*a_s)-(0-V_t ²)/(2*a_t)；

T is the brake reaction time, V_sIs the speed of the bicycle, V_tIs the target vehicle speed, a_sIs the acceleration of the bicycle, a_tIs the target vehicle acceleration, t_ssIs the time required for the vehicle to stop, t_tsIs the time required for the target vehicle to stop.

Optionally, the safety distance calculation method is further improved, when the front target vehicle stops first, stops after the vehicle stops, t_ts＜t_ssAt > T, the required safety distance is

d＝V_s*T+1/2*a_s*T²+(0-(V_s+a_s*T)²)/(2*a_min)-(0-V_t ²)/(2*a_t)；

T is the brake reaction time, d is the required safety distance, V_sIs the speed of the bicycle, V_tIs the target vehicle speed, a_sIs the acceleration of the bicycle, a_tIs the target vehicle acceleration, t_ssIs the time required for the vehicle to stop, t_tsIs the time required for the target vehicle to stop, a_minIs the maximum deceleration produced by wheel braking, in units: m/s²。

Optionally, the safety distance calculation method is further improved, if t epsilon (0, t)_ss) The required safety distance is d ═ V_s-V_t)*t+1/2*(a_s-a_t)*t²；

d is the desired safety distance, V_sIs the speed of bicycle, V_tIs the target vehicle speed, a_sIs the acceleration of the bicycle, a_tIs the target vehicle acceleration, and t is the time required for both vehicles to reach a constant speed.

Optionally, the safety distance calculation method is further improved if t_ts＜t_ssIf there is only one constant speed moment, the safety distance is

d＝V_s*T+1/2*a_s*T²+(V_s+a_s*T)*t_x+1/2*a_min*t_x ²-(V_t*(T+t_x)+1/2*at*(T+t_x)²) ；

T is the brake reaction time, d is the required safety distance, V_sIs the speed of the bicycle, V_tIs the target vehicle speed, a_sIs the acceleration of the bicycle, a_tIs the target vehicle acceleration, t_xIs the time required for the two vehicles to reach a constant speed after T, a_minIs the maximum deceleration produced by wheel braking, in units: m/s²。

Optionally, the safety distance calculation method is further improved, and the safety distance required at the second constant speed moment is

d is the desired safety distance, V_sIs the speed of the bicycle, a_sIs the acceleration of the bicycle, a_tIs the target vehicle acceleration, V_tIs the target vehicle speed, t_yIs the time required for the second time of the last two cars to reach the constant speed, a_minIs the maximum deceleration produced by wheel braking, in units: m/s²。

Alternatively, in step S3, if the target vehicle and the host vehicle are traveling at the same constant speed, the required safe distance is d-V_sT, T is the brake reaction time, V_sIs the speed of the vehicle.

Optionally, the safety distance calculation method is further improved, in step S3, if a is_t＝0，V_tIf Vs is 0 in the braking reaction time of the bicycle, the required safety distance is d (0-V)_s ²)/(2*a_s)；

If Vs is more than 0 in the braking reaction time of the self-vehicle, the required safety distance is

d＝V_s*T+1/2*a_s*T²+(0-(V_s+a_s*T)²)/(2*a_min)；

T is the brake reaction time, d is the required safety distance, V_sIs the speed of the bicycle, a_sIs the acceleration of the bicycle, a_tIs the target vehicle acceleration, V_tIs the target vehicle speed, a_minIs the maximum deceleration produced by wheel braking, in units: m/s²。

The invention comprehensively considers the kinematic parameters of the distance, the speed, the acceleration and the like of the self vehicle and the target vehicle, analyzes the most dangerous moment of the self vehicle in the current state, calculates the minimum safe distance for ensuring that the vehicle does not collide, and provides a safe distance threshold value for the forward collision alarm FCW and the emergency brake AEB.

The analysis of the motion state is to find the most dangerous moment and calculate the minimum safe distance, and the motion state of the self vehicle is assumed as follows: in the braking reaction time T, making uniform acceleration movement for keeping the current acceleration; then, the uniform deceleration movement is carried out with the maximum braking force until the stop. The possible motion states of the speed of the bicycle versus time are shown in fig. 2. The motion state of the bicycle is divided into the following 3 types:

uniformly accelerating movement within braking reaction time T, and uniformly decelerating movement with maximum braking force after T;

uniformly moving within the braking reaction time T, and uniformly decelerating with the maximum braking force after T;

and thirdly, performing uniform deceleration motion within the braking reaction time T, and performing uniform deceleration motion with the maximum braking force after T.

The motion state of the target vehicle is: maintaining uniform acceleration motion of the current acceleration, comprising: uniform acceleration motion, uniform motion and uniform deceleration motion. As shown in fig. 3.

Judging the most dangerous moment, and when the speed of the vehicle is higher than the speed of the target vehicle, the distance between the vehicle and the target vehicle is reduced, and the danger is increased; when the speed of the vehicle is lower than the speed of the target vehicle, the distance between the vehicle and the target vehicle is increased, and the collision risk is reduced; when the speeds of the host vehicle and the target vehicle are equal, there may be a mutual turning point of safety and danger. Therefore, the most dangerous moment can be determined according to the size of the speed-time image value of the vehicle and the speed-time image value of the target vehicle, the existence of the intersection point of the speed images, the number of the speed intersection points and the position of the intersection point in the same coordinate system. Emergency braking is a uniform deceleration motion with constant acceleration until the speed is reduced to 0 and remains stationary. Therefore, the condition that the vehicle is uniformly decelerated to zero and is continuously backed is not considered; the case where the target vehicle is in front of the rear-end collision or the target vehicle is suddenly stopped against the wall, i.e., the front vehicle is normally braked (brake deceleration is at most-g), is not considered.

Calculating the time t required for parking the host vehicle and the target vehicle_ssAnd t_ts；

(V_s+a_sWhen x T) > 0, the time required for stopping the bicycle is

(V_s+a_sX T) is less than or equal to 0, the time required for stopping the bicycle is

T is the brake reaction time, V_sIs the speed of the bicycle, a_sIs the acceleration of the bicycle, a_minIs the maximum deceleration produced by wheel braking, in units: m/s²。

a_tIf > 0, then t_ts＝∞；

a_t0 and V_tNot equal to 0, then t_ts＝∞；

a_t0 and V_tWhen t is equal to 0_ts＝0；

a_tIf less than 0, then

a_tIs the target vehicle acceleration, V_tIs the target vehicle speed.

And classifying the working conditions of the vehicle according to the stopping sequence of the vehicle and the target vehicle and whether the stopping is within the system delay time T, and further specifically analyzing the safety distance corresponding to the most dangerous moment under various conditions.

When the vehicle stops after the vehicle stops, the target vehicle stops firstly, the distance between the vehicle and the target is always reduced, the risk of collision is increased, and therefore the vehicle is most dangerous when stopping;

case 1;

when the front target vehicle stops first, then stops after the vehicle stops, and t_ts＜t_ssDistance d traveled by the vehicle < T_s＝(0-V_s ²)/(2*a_s) Distance d traveled by the target vehicle_t＝(0-V_t ²)/(2*a_t) The required safety distance is d ═ d_s-d_t＝(0-V_s ²)/(2*a_s)-(0-V_t ²)/(2*a_t)。

Case 2;

when the front target vehicle stops first, then stops after the vehicle stops, t_ts＜t_ssWhen more than T, the distance d of the vehicle_s＝V_s*T+1/2*a_s*T²+(0-(V_s+a_s*T)²)/(2*a_min) Distance d traveled by the target vehicle_t＝(0-V_t ²)/(2*a_t) The required safety distance is d ═ d_s-d_t＝V_s*T+1/2*a_s*T²+(0-(V_s+a_s*T)²)/(2*a_min)-(0-V_t ²)/(2*a_t)。

When the vehicle stops first t_ss＜t_tsIn time, the most dangerous moment needs to be determined by looking up whether and the number of the existing equivelocity.

Case 3;

the vehicle stopping first and during the braking reaction time, assuming constant speed, i.e. V_s+a_s*t＝V_t+a_tT, can obtain t ═ V_t-V_s)/(a_s-a_t) If t is equal to (0, t)_ss) I.e. there is a constant velocity, e.g. V in FIG. 4_t1As shown, the safety distance required for the vehicle to stop at the same speed is d ═ V (the safe distance is most dangerous from the start to the same speed_s-V_t)*t+1/2*(a_s-a_t)*t²；

Case 4;

if the target vehicle and the host vehicle do not have the constant speed time no matter within the braking reaction time or outside the braking reaction time, the host vehicle speed is always lower than the target vehicle speed, and the safety distance d required for safety is kept equal to 0.

Case 5;

front target vehicle rear stop t_ss＜t_tsAnd when the bicycle is in braking reactionIntermittent and external first stop t_ss＞T；

If the target vehicle and the host vehicle only have one constant speed moment, and the constant speed moment is out of the braking reaction time, the constant speed moment is the most dangerous moment;

t after setting T_xPresent at a constant velocity in seconds, i.e. V_s+a_s*T+a_min*t_x＝V_t+a_t*(T+t_x) Thus, t can be obtained_x＝(V_t-V_s+(a_t-a_s)*T)/(a_min-a_t) Then, determine t_xWhether it belongs to (0, (0- (V)_s+a_s*T))/a_min). When there is an equi-velocity outside T (i.e. T)_xWithin the specified range) is most dangerous at constant speed, the required safety distance is d ═ V_s*T+1/2*a_s*T2+(V_s+a_s*T)*t_x+1/2*a_min*t_x ²-(V_t*(T+t_x)+1/2*a_t*(T+t_x)²)

Case 6;

front target vehicle rear stop t_ss＜t_tsAnd the bicycle stops t before the braking reaction time_ss＞T；

If the target vehicle and the self vehicle have two constant speed moments which are out of the braking reaction time, the second coming constant speed moment is the most dangerous moment; the second constant speed moment requires a safety distance of

Case 7;

when the host vehicle and the target vehicle both run at a constant speed, it is assumed that the target vehicle can perform emergency braking at any time in order to ensure that the host vehicle does not collide with the target vehicle, as shown in fig. 5. At this time, the safety distance to be maintained is

d＝d₁-d₂＝(V_s*T+(0-V_s ²)/(2*a_min))-(0-V_t ²)/(2*a_min)＝V_s*T。

Case 8;

if a_t＝0，V_tThe target vehicle remains stationary at 0, and the required safe distance is the distance at which the own vehicle decelerates from the current speed to 0. The deceleration of the self vehicle to 0 at most needs to pass through the uniform acceleration movement within the system delay time T and the deceleration to 0 with the maximum braking force

a_t＝0，V_tIf Vs is 0 in the braking reaction time of the bicycle, the required safety distance is d (0-V)_s ²)/(2*a_s)；

If Vs is more than 0 in the braking reaction time of the self-vehicle, the required safety distance is d-V_s*T+1/2*a_s*T²+(0-(V_s+a_s*T)²)/(2*a_min)。

According to the relative motion state between the vehicle and the target vehicle, the relative distance, the speed and the acceleration of the vehicle and the target vehicle are comprehensively considered, and the safety distance of emergency braking of the vehicle is calculated by analyzing the parking sequence of the vehicle and the target vehicle and the number and the positions of the constant speed points, wherein the safety distance is the minimum distance for ensuring that the vehicle does not collide. The minimum distance can reduce the false alarm rate of FCW and the false touch rate of AEB, improve the use effect of ADAS products and enhance the competitiveness of the products. The invention has important practical application value, the safe distance of the invention is calculated under an ideal state, the actual vehicle running condition is more complex, for example, the braking reaction time is a fixed value in the calculation, and the braking reaction time can slightly change (the temperature influences the processing speed and the like) in the actual vehicle form. The safety distance calculated by the theory of the invention is smaller than the calculated result of the traditional method, and a certain safety margin distance value can be added in the actual application, thereby further ensuring that no collision occurs.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention, are incorporated in and constitute a part of this specification. The drawings are not necessarily to scale, however, and may not be intended to accurately reflect the precise structural or performance characteristics of any given embodiment, and should not be construed as limiting or restricting the scope of values or properties encompassed by exemplary embodiments in accordance with the invention. The invention will be described in further detail with reference to the following detailed description and accompanying drawings:

fig. 1 is a schematic structural diagram of a safe distance calculation module according to the present invention.

Fig. 2 is a graph of speed-time variation of a possible motion state of the own vehicle.

Fig. 3 is a target vehicle speed-time change diagram.

Fig. 4 is a speed-time diagram of the first stop of the vehicle during a braking reaction time.

Fig. 5 is a speed-time diagram for two vehicles traveling at the same speed.

Fig. 6 is a graph of final stopping speed of the vehicle during a braking reaction time versus time.

Fig. 7 is a graph of final stopping speed of the vehicle outside the braking response time versus time.

Fig. 8 is a speed-time diagram for the case where the vehicle stops first and there is a constant speed outside the brake reaction time.

Detailed Description

The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and technical effects of the present invention will be fully apparent to those skilled in the art from the disclosure in the specification. The invention is capable of other embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the general spirit of the invention. It is to be noted that the features in the following embodiments and examples may be combined with each other without conflict. The following exemplary embodiments of the present invention may be embodied in many different forms and should not be construed as limited to the specific embodiments set forth herein. It is to be understood that these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the technical solutions of these exemplary embodiments to those skilled in the art.

As shown in fig. 1, a first embodiment of a safe distance calculating module of the present invention, which is used for an automatic emergency braking system of a vehicle and/or a vehicle front collision warning system, includes:

the system comprises a data acquisition unit, a data processing unit and a control unit, wherein the data acquisition unit is suitable for acquiring the relative distance between a self vehicle and a target vehicle, the speed of the self vehicle, the speed of the target vehicle, the acceleration of the self vehicle, the acceleration of the target vehicle and the braking reaction time;

a most dangerous moment calculation unit adapted to determine a most dangerous moment based on the own vehicle speed, the own vehicle stop required time, the target vehicle speed, the target vehicle stop required time, the own vehicle acceleration, and the target vehicle acceleration;

and the minimum emergency braking distance calculation unit is used for calculating the difference value of the running distance of the self vehicle from the target vehicle at the most dangerous moment according to the sequence of the self vehicle stopping and the target vehicle stopping and whether the time required by the target vehicle stopping and the time required by the self vehicle stopping are within the braking reaction time, wherein the distance difference value is the minimum emergency braking distance.

According to the relative motion state between the vehicle and the target vehicle, the relative distance, the speed and the acceleration of the vehicle and the target vehicle are comprehensively considered, and the safety distance of emergency braking of the vehicle is calculated by analyzing the parking sequence of the vehicle and the target vehicle and the number and the positions of the constant speed points, wherein the safety distance is the minimum distance for ensuring that the vehicle does not collide. The minimum distance can reduce the false alarm rate of FCW and the false touch rate of AEB, improve the use effect of ADAS products and enhance the competitiveness of the products.

The invention relates to a safe distance calculating module used for a vehicle automatic emergency braking system and/or a vehicle front collision early warning system, which comprises:

the system comprises a data acquisition unit, a data processing unit and a control unit, wherein the data acquisition unit is suitable for acquiring the relative distance between a self vehicle and a target vehicle, the speed of the self vehicle, the speed of the target vehicle, the acceleration of the self vehicle, the acceleration of the target vehicle and the braking reaction time; the brake reaction time comprises data acquisition time, data analysis time, emergency brake decision making time, brake clearance elimination time and time for increasing the brake force from zero to the maximum.

Optionally, the data acquisition unit comprisesWheel pulse sensors, millimeter wave radar, and acceleration sensors. The wheel pulse sensor is used for obtaining the wheel speed, and the vehicle speed V can be obtained through kinematic analysis; the millimeter wave radar obtains the relative distance d between the vehicle and the target vehicle_rRelative velocity V_rRelative acceleration a_rInformation; acceleration sensor for obtaining acceleration a of vehicle_s. And further can be obtained by calculation, the target vehicle speed V_tTarget vehicle acceleration a_t。

A most dangerous moment calculation unit adapted to determine a most dangerous moment based on the own vehicle speed, the own vehicle stop required time, the target vehicle speed, the target vehicle stop required time, the own vehicle acceleration, and the target vehicle acceleration;

alternatively, the first and second electrodes may be,

the calculation mode of the time required by the stop of the self vehicle is as follows;

(V_s+a_swhen x T) > 0, the time required for stopping the bicycle is

(V_s+a_sX T) is less than or equal to 0, the time required for stopping the bicycle is

The target vehicle stop required time is calculated as follows;

a_tif > 0, then t_ts＝∞；

a_t0 and V_tNot equal to 0, then t_ts＝∞；

a_t0 and V_tWhen t is equal to 0_ts＝0；

a_tIf less than 0, then

And the minimum emergency braking distance calculation unit is used for calculating the difference value of the running distance of the self vehicle from the target vehicle at the most dangerous moment according to the sequence of the self vehicle stopping and the target vehicle stopping and whether the time required by the target vehicle stopping and the time required by the self vehicle stopping are within the braking reaction time, wherein the distance difference value is the minimum emergency braking distance.

Optionally, the most dangerous moment calculation unit and/or the minimum emergency braking distance calculation unit may be implemented by an independent MCU, or by an MCU of a vehicle automatic emergency braking system and/or a vehicle front collision warning system.

The current target vehicle stops firstly, and stops after the vehicle stops, and the vehicle stops at the most dangerous moment.

If the target vehicle and the host vehicle do not have the constant speed time no matter within the braking reaction time or outside the braking reaction time, the host vehicle speed is always lower than the target vehicle speed, and the safety distance d required for safety is kept equal to 0.

Front target vehicle rear stop, t_ss＜t_tsAnd the bicycle stops T within the time T first_ss＜T；

If the target vehicle and the host vehicle only have one constant speed moment, and the constant speed moment is within the braking reaction time, the constant speed moment is the most dangerous moment;

t is the brake reaction time, T_ssIs the time required for the vehicle to stop, t_tsIs the time required for the target vehicle to stop.

Front target vehicle rear stop t_ss＜t_tsAnd the bicycle stops t before the braking reaction time_ss＞T；

If the target vehicle and the host vehicle only have one constant speed moment, and the constant speed moment is out of the braking reaction time, the constant speed moment is the most dangerous moment;

if the target vehicle and the self vehicle have two constant speed moments which are out of the braking reaction time, the second coming constant speed moment is the most dangerous moment;

when the front target vehicle stops first, then stops after the vehicle stops, and t_ts＜t_ssWhen < T, the required safety distance is

d＝(0-V_s ²)/(2*a_s)-(0-V_t ²)/(2*a_t)；

When the front target vehicle stops first, then stops after the vehicle stops, t_ts＜t_ssAt > T, the required safety distance is

d＝V_s*T+1/2*a_s*T²+(0-(V_s+a_s*T)²)/(2*a_min)-(0-V_t ²)/(2*a_t)；

If t is an element of (0, t)_ss) The required safety distance is d ═ V_s-V_t)*t+1/2*(a_s-a_t)*t²；

If t_ts＜t_ssIf there is only one constant speed moment, the safety distance is

d＝V_s*T+1/2*a_s*T²+(V_s+a_s*T)*t_x+1/2*a_min*t_x ²-(V_t*(T+t_x)+1/2*a_t*(T+t_x)²) ；

The second constant speed moment requires a safety distance of

If the target vehicle and the self vehicle run at the same speed, the required safe distance is d-V_s*T；

If a_t＝0，V_tIf Vs is 0 in the braking reaction time of the bicycle, the required safety distance is d (0-V)_s ²)/(2*a_s)；

If Vs is more than 0 in the braking reaction time of the self-vehicle, the required safety distance is d-V_s*T+1/2*a_s*T²+(0-(V_s+a_s*T)²)/(2*a_min)；

T is the brake reaction time, d is the required safety distance, V_sIs the speed of the bicycle, V_tIs the target vehicle speed, a_sIs the acceleration of the bicycle, a_tIs the target vehicle acceleration, t_ssIs the time required for the vehicle to stop, t_tsIs the time required for the target vehicle to stop, t_xIs required for the two vehicles behind T to reach the constant speedTime, t_yIs the time required for the second time of the last two cars to reach the constant speed, a_minIs the maximum deceleration produced by wheel braking, in units: m/s²。

The invention provides a first embodiment of a safe distance calculation method for calculating the safe distance of automatic emergency braking of a vehicle and/or calculating the early warning safe distance of collision in front of the vehicle, which comprises the following steps:

s1, acquiring the relative distance between the vehicle and the target vehicle, the vehicle speed, the target vehicle speed, the vehicle acceleration, the target vehicle acceleration and the brake reaction time;

s2, determining the most dangerous moment according to the speed of the vehicle, the time required for stopping the vehicle, the speed of the target vehicle, the time required for stopping the target vehicle, the acceleration of the vehicle and the acceleration of the target vehicle;

and S3, calculating the difference value of the running distance of the vehicle from the target vehicle at the most dangerous moment according to the sequence of the stop of the vehicle and the stop of the target vehicle and whether the time required by the stop of the target vehicle and the time required by the stop of the vehicle are within the braking reaction time, wherein the distance difference value is the minimum emergency braking distance.

According to the relative motion state between the vehicle and the target vehicle, the relative distance, the speed and the acceleration of the vehicle and the target vehicle are comprehensively considered, and the safety distance of emergency braking of the vehicle is calculated by analyzing the parking sequence of the vehicle and the target vehicle and the number and the positions of the constant speed points, wherein the safety distance is the minimum distance for ensuring that the vehicle does not collide.

It will be further understood that, although the terms first, second, etc. may be used herein to describe various elements, parameters, components, regions, layers and/or sections, these elements, parameters, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, parameter, component, region, layer or section from another element, parameter, component, region, layer or section. Thus, a first element, parameter, component, region, layer or section discussed below could be termed a second element, parameter, component, region, layer or section without departing from the teachings of exemplary embodiments according to the present invention.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

The invention provides a second embodiment of a safe distance calculation method for calculating the safe distance of automatic emergency braking of a vehicle and/or calculating the early warning safe distance of collision in front of the vehicle, which comprises the following steps:

s1, acquiring the relative distance between the vehicle and the target vehicle, the vehicle speed, the target vehicle speed, the vehicle acceleration, the target vehicle acceleration and the brake reaction time;

s2, determining the most dangerous moment according to the speed of the vehicle, the time required for stopping the vehicle, the speed of the target vehicle, the time required for stopping the target vehicle, the acceleration of the vehicle and the acceleration of the target vehicle;

the calculation mode of the time required by the stop of the self vehicle is as follows;

(V_s+a_swhen x T) > 0, the time required for stopping the bicycle is

(V_s+a_sX T) is less than or equal to 0, the time required for stopping the bicycle is

The target vehicle stop required time is calculated as follows;

a_tif > 0, then t_ts＝∞；

a_t0 and V_tNot equal to 0, then t_ts＝∞；

a_t0 and V_tWhen t is equal to 0_ts＝0；

a_tIf less than 0, then

And S3, calculating the difference value of the running distance of the vehicle from the target vehicle at the most dangerous moment according to the sequence of the stop of the vehicle and the stop of the target vehicle and whether the time required by the stop of the target vehicle and the time required by the stop of the vehicle are within the braking reaction time, wherein the distance difference value is the minimum emergency braking distance.

The current target vehicle stops firstly, and stops after the vehicle stops, and the vehicle stops at the most dangerous moment.

If the target vehicle and the host vehicle do not have the constant speed time no matter within the braking reaction time or outside the braking reaction time, the host vehicle speed is always lower than the target vehicle speed, and the safety distance d required for safety is kept equal to 0.

Front target vehicle rear stop, t_ss＜t_tsAnd the bicycle stops T within the time T first_ss＜T；

If the target vehicle and the host vehicle only have one constant speed moment, and the constant speed moment is within the braking reaction time, the constant speed moment is the most dangerous moment;

t is the brake reaction time, T_ssIs the time required for the vehicle to stop, t_tsIs the time required for the target vehicle to stop.

Front target vehicle rear stop t_ss＜t_tsAnd the bicycle stops t before the braking reaction time_ss＞T；

If the target vehicle and the host vehicle only have one constant speed moment, and the constant speed moment is out of the braking reaction time, the constant speed moment is the most dangerous moment;

if the target vehicle and the self vehicle have two constant speed moments which are out of the braking reaction time, the second coming constant speed moment is the most dangerous moment;

when the front target vehicle stops first, then stops after the vehicle stops, and t_ts＜t_ssWhen < T, the required safety distance is

d＝(0-V_s ²)/(2*a_s)-(0-V_t ²)/(2*a_t)；

When the front target vehicle stops first, then stops after the vehicle stops, t_ts＜t_ssAt > T, the required safety distance is

d＝V_s*T+1/2*a_s*T²+(0-(V_s+a_s*T)²)/(2*a_min)-(0-V_t ²)/(2*a_t)；

If t is an element of (0, t)_ss) The required safety distance is d ═ V_s-V_t)*t+1/2*(a_s-a_t)*t²；

If t_ts＜t_ssIf there is only one constant speed moment, the safety distance is

d＝V_s*T+1/2*a_s*T²+(V_s+a_s*T)*t_x+1/2*a_min*t_x ²-(V_t*(T+t_x)+1/2*a_t*(T+t_x)²) ；

The second constant speed moment requires a safety distance of

If the target vehicle and the self vehicle run at the same speed, the required safe distance is d-V_s*T；

If a_t＝0，V_tIf Vs is 0 in the braking reaction time of the bicycle, the required safety distance is d (0-V)_s ²)/(2*a_s)；

If Vs is more than 0 in the braking reaction time of the self-vehicle, the required safety distance is d-V_s*T+1/2*a_s*T²+(0-(V_s+a_s*T)²)/(2*a_min)；

T is the brake reaction time, d is the required safety distance, V_sIs the speed of the bicycle, V_tIs the target vehicle speed, a_sIs the acceleration of the bicycle, a_tIs the target vehicle acceleration, t_ssIs the time required for the vehicle to stop, t_tsIs the time required for the target vehicle to stop, t_xIs the time required for the last two cars to reach a constant speed, T_yIs the time required for the second time of the last two cars to reach the constant speed, a_minIs the maximum deceleration produced by wheel braking, in units: m/s²。

The present invention has been described in detail with reference to the specific embodiments and examples, but these are not intended to limit the present invention. Many variations and modifications may be made by one of ordinary skill in the art without departing from the principles of the present invention, which should also be considered as within the scope of the present invention.

Claims (30)

1. A safe distance calculation module for use in an automatic emergency braking system for a vehicle and or a vehicle forward collision warning system, comprising:

the system comprises a data acquisition unit, a data processing unit and a control unit, wherein the data acquisition unit is suitable for acquiring the relative distance between a self vehicle and a target vehicle, the speed of the self vehicle, the speed of the target vehicle, the acceleration of the self vehicle, the acceleration of the target vehicle and the braking reaction time;

a most dangerous moment calculation unit adapted to determine a most dangerous moment based on the own vehicle speed, the own vehicle stop required time, the target vehicle speed, the target vehicle stop required time, the own vehicle acceleration, and the target vehicle acceleration;

and the minimum emergency braking distance calculation unit is used for calculating the difference value of the running distance of the self vehicle from the target vehicle at the most dangerous moment according to the sequence of the self vehicle stopping and the target vehicle stopping and whether the time required by the target vehicle stopping and the time required by the self vehicle stopping are within the braking reaction time, wherein the distance difference value is the minimum emergency braking distance.

2. The safe distance computation module of claim 1, wherein: the brake reaction time comprises data acquisition time, data analysis time, emergency brake decision making time, brake clearance elimination time and time for increasing the brake force from zero to the maximum.

3. The safe distance computation module of claim 1, wherein: the calculation mode of the time required by the stop of the self vehicle is as follows;

(V_s+a_swhen x T) > 0, the time required for stopping the bicycle is

(V_s+a_sX T) is less than or equal to 0, the time required for stopping the bicycle is

T is the brake reaction time, V_sIs the speed of the bicycle, a_sIs the acceleration of the bicycle, a_minIs the maximum deceleration produced by wheel braking, in units: m/s²。

4. A safe distance calculation module as defined in claim 3, wherein: the target vehicle stop required time is calculated as follows;

a_tif > 0, then t_ts＝∞；

a_t0 and V_tNot equal to 0, then t_ts＝∞；

a_t0 and V_tWhen t is equal to 0_ts＝0；

a_tIf less than 0, then

a_tIs the target vehicle acceleration, V_tIs the target vehicle speed, t_tsIs the time required for the target vehicle to stop.

5. The safe distance computation module of claim 4, wherein: when the front target vehicle stops firstly, the vehicle stops after the vehicle stops, and the vehicle stops at the most dangerous moment.

6. The safe distance computation module of claim 4, wherein:

if the target vehicle and the host vehicle do not have the constant speed time no matter within the braking reaction time or outside the braking reaction time, the host vehicle speed is always lower than the target vehicle speed, and the safety distance d required for safety is kept equal to 0.

7. The safe distance computation module of claim 4, wherein: front target vehicle rear stop, t_ss＜t_tsAnd the bicycle stops T within the time T first_ss＜T；

If the target vehicle and the host vehicle only have one constant speed moment, and the constant speed moment is within the braking reaction time, the constant speed moment is the most dangerous moment;

t is the brake reaction time, T_ssIs the time required for the vehicle to stop, t_tsIs the time required for the target vehicle to stop.

8. The safe distance computation module of claim 4, wherein: front target vehicle rear stop t_ss＜t_tsAnd the bicycle stops t before the braking reaction time_ss＞T；

If the target vehicle and the host vehicle only have one constant speed moment, and the constant speed moment is out of the braking reaction time, the constant speed moment is the most dangerous moment;

if the target vehicle and the self vehicle have two constant speed moments which are out of the braking reaction time, the second coming constant speed moment is the most dangerous moment;

t is the brake reaction time, T_ssIs the time required for the vehicle to stop, t_tsIs the time required for the target vehicle to stop.

9. The safe distance computation module of claim 5, wherein: when the front target vehicle stops first, then stops after the vehicle stops, and t_ts＜t_ssWhen < T, the required safety distance is

d＝(0-V_s ²)/(2*a_s)-(0-V_t ²)/(2*a_t)；

T is the brake reaction time, V_sIs the speed of the bicycle，V_tIs the target vehicle speed, a_sIs the acceleration of the bicycle, a_tIs the target vehicle acceleration, t_ssIs the time required for the vehicle to stop, t_tsIs the time required for the target vehicle to stop.

10. The safe distance computation module of claim 5, wherein: when the front target vehicle stops first, then stops after the vehicle stops, t_ts＜t_ssAt > T, the required safety distance is

d＝V_s*T+1/2*a_s*T²+(0-(V_s+a_s*T)²)/(2*a_min)-(0-V_t ²)/(2*a_t)；

T is the brake reaction time, d is the required safety distance, V_sIs the speed of the bicycle, V_tIs the target vehicle speed, a_sIs the acceleration of the bicycle, a_tIs the target vehicle acceleration, t_ssIs the time required for the vehicle to stop, t_tsIs the time required for the target vehicle to stop, a_minIs the maximum deceleration produced by wheel braking, in units: m/s²。

11. The safe distance computation module of claim 7, wherein:

if t is an element of (0, t)_ss) The required safety distance is d ═ V_s-V_t)*t+1/2*(a_s-a_t)*t²；

d is the desired safety distance, V_sIs the speed of the bicycle, V_tIs the target vehicle speed, a_sIs the acceleration of the bicycle, a_tIs the target vehicle acceleration, and t is the time required for both vehicles to reach a constant speed.

12. The safe distance computation module of claim 8, wherein: if t_ts＜t_ssIf there is only one constant speed moment, the safety distance is

d＝V_s*T+1/2*a_s*T²+(V_s+a_s*T)*t_x+1/2*a_min*t_x ²-(V_t*(T+t_x)+1/2*a_t*(T+t_x)²)；

T is the brake reaction time, d is the required safety distance, V_sIs the speed of the bicycle, V_tIs the target vehicle speed, a_sIs the acceleration of the bicycle, a_tIs the target vehicle acceleration, t_xIs the time required for the two vehicles to be at the same speed after T, a_minIs the maximum deceleration produced by wheel braking, in units: m/s²。

13. The safe distance computation module of claim 8, wherein: the second constant speed moment requires a safety distance of

d is the desired safety distance, V_sIs the speed of the bicycle, a_sIs the acceleration of the bicycle, a_tIs the target vehicle acceleration, V_tIs the target vehicle speed, t_yIs the time required for the second time of the last two cars to reach the constant speed, a_minIs the maximum deceleration produced by wheel braking, in units: m/s²。

14. The safe distance computation module of claim 1, wherein:

if the target vehicle and the self vehicle run at the same speed, the required safe distance is d-V_sT, T is the brake reaction time, V_sIs the speed of the vehicle.

15. The safe distance computation module of claim 1, wherein:

a_t＝0，V_tif Vs is 0 in the braking reaction time of the bicycle, the required safety distance is 0

d＝(0-V_s ²)/(2*a_s)；

If Vs is more than 0 in the braking reaction time of the self-vehicle, the required safety distance is

d＝V_s*T+1/2*a_s*T²+(0-(V_s+a_s*T)²)/(2*a_min)；

T is the brake reaction time, d is the required safety distance, V_sIs the speed of the bicycle, a_sIs the acceleration of the bicycle, a_tIs the target vehicle acceleration, V_tIs the target vehicle speed, a_minIs the maximum deceleration produced by wheel braking, in units: m/s²。

16. A safe distance calculation method is used for calculating the safe distance of automatic emergency braking of a vehicle and/or calculating the early warning safe distance of collision in front of the vehicle, and is characterized by comprising the following steps:

s1, acquiring the relative distance between the vehicle and the target vehicle, the vehicle speed, the target vehicle speed, the vehicle acceleration, the target vehicle acceleration and the brake reaction time;

s2, determining the most dangerous moment according to the speed of the vehicle, the time required for stopping the vehicle, the speed of the target vehicle, the time required for stopping the target vehicle, the acceleration of the vehicle and the acceleration of the target vehicle;

and S3, calculating the difference value of the running distance of the vehicle from the target vehicle at the most dangerous moment according to the sequence of the stop of the vehicle and the stop of the target vehicle and whether the time required by the stop of the target vehicle and the time required by the stop of the vehicle are within the braking reaction time, wherein the distance difference value is the minimum emergency braking distance.

17. The safe distance calculation method according to claim 16, characterized in that: in step S3, the brake response time includes data acquisition time, data analysis time, time for making an emergency braking decision, time for eliminating a brake clearance, and time for increasing a braking force from zero to a maximum.

18. The safe distance calculation method according to claim 16, characterized in that: in step S2, the calculation method of the required stop time of the vehicle is as follows;

(V_s+a_swhen x T) > 0, the bicycle stopsThe required time is

(V_s+a_sX T) is less than or equal to 0, the time required for stopping the bicycle is

T is the brake reaction time, V_sIs the speed of the bicycle, a_sIs the acceleration of the bicycle, a_minIs the maximum deceleration produced by wheel braking, in units: m/s²。

19. The safe distance calculation method according to claim 18, wherein: the target vehicle stop required time is calculated as follows;

a_tif > 0, then t_ts＝∞；

a_t0 and V_tNot equal to 0, then t_ts＝∞；

a_t0 and V_tWhen t is equal to 0_ts＝0；

a_tIf less than 0, then

a_tIs the target vehicle acceleration, V_tIs the target vehicle speed, t_tsIs the time required for the target vehicle to stop.

20. The safe distance calculation method according to claim 19, wherein: when the front target vehicle stops firstly, the vehicle stops after the vehicle stops, and the vehicle stops at the most dangerous moment.

21. The safe distance calculation method according to claim 19, wherein:

if the target vehicle and the host vehicle do not have the constant speed time no matter within the braking reaction time or outside the braking reaction time, the host vehicle speed is always lower than the target vehicle speed, and the safety distance d required for safety is kept equal to 0.

22. The safe distance calculation method according to claim 19, wherein:

front target vehicle rear stop, t_ss＜t_tsAnd the bicycle stops T within the time T first_ss＜T；

If the target vehicle and the host vehicle only have one constant speed moment, and the constant speed moment is within the braking reaction time, the constant speed moment is the most dangerous moment;

t is the brake reaction time, T_ssIs the time required for the vehicle to stop, t_tsIs the time required for the target vehicle to stop.

23. The safe distance calculation method according to claim 19, wherein:

front target vehicle rear stop t_ss＜t_tsAnd the bicycle stops t before the braking reaction time_ss＞T；

If the target vehicle and the host vehicle only have one constant speed moment, and the constant speed moment is out of the braking reaction time, the constant speed moment is the most dangerous moment;

if the target vehicle and the self vehicle have two constant speed moments which are out of the braking reaction time, the second coming constant speed moment is the most dangerous moment;

t is the brake reaction time, T_ssIs the time required for the vehicle to stop, t_tsIs the time required for the target vehicle to stop.

24. The safe distance calculation method according to claim 20, wherein:

when the front target vehicle stops first, then stops after the vehicle stops, and t_ts＜t_ssWhen < T, the required safety distance is

d＝(0-V_s ²)/(2*a_s)-(0-V_t ²)/(2*a_t)；

T is the brake reaction time, V_sIs the speed of the bicycle, V_tIs a target vehicleSpeed, a_sIs the acceleration of the bicycle, a_tIs the target vehicle acceleration, t_ssIs the time required for the vehicle to stop, t_tsIs the time required for the target vehicle to stop.

25. The safe distance calculation method according to claim 20, wherein:

when the front target vehicle stops first, then stops after the vehicle stops, t_ts＜t_ssAt > T, the required safety distance is

d＝V_s*T+1/2*a_s*T²+(0-(V_s+a_s*T)²)/(2*a_min)-(0-V_t ²)/(2*a_t)；

T is the brake reaction time, d is the required safety distance, V_sIs the speed of the bicycle, V_tIs the target vehicle speed, a_sIs the acceleration of the bicycle, a_tIs the target vehicle acceleration, t_ssIs the time required for the vehicle to stop, t_tsIs the time required for the target vehicle to stop, a_minIs the maximum deceleration produced by wheel braking, in units: m/s²。

26. The safe distance calculation method according to claim 22, wherein:

if t is an element of (0, t)_ss) The required safety distance is d ═ V_s-V_t)*t+1/2*(a_s-a_t)*t²；

d is the desired safety distance, V_sIs the speed of bicycle, V_tIs the target vehicle speed, a_sIs the acceleration of the bicycle, a_tIs the target vehicle acceleration, and t is the time required for both vehicles to reach a constant speed.

27. The safe distance calculating method according to claim 23, wherein:

if t_ts＜t_ssIf there is only one constant speed moment, the safety distance is

d＝V_s*T+1/2*a_s*T²+(V_s+a_s*T)*t_x+1/2*a_min*t_x ²-(V_t*(T+t_x)+1/2*a_t*(T+t_x)²)；

T is the brake reaction time, d is the required safety distance, V_sIs the speed of the bicycle, V_tIs the target vehicle speed, a_sIs the acceleration of the bicycle, a_tIs the target vehicle acceleration, t_xIs the time required for the two vehicles to reach a constant speed after T, a_minIs the maximum deceleration produced by wheel braking, in units: m/s²。

28. The safe distance computation module of claim 23, wherein:

the second constant speed moment requires a safety distance of

d is the desired safety distance, V_sIs the speed of the bicycle, a_sIs the acceleration of the bicycle, a_tIs the target vehicle acceleration, V_tIs the target vehicle speed, t_yIs the time required for the second time of the last two cars to reach the constant speed, a_minIs the maximum deceleration produced by wheel braking, in units: m/s²。

29. The safe distance calculation method according to claim 16, characterized in that: in step S3, if the target vehicle travels at a constant speed equal to the speed of the vehicle, the required safe distance is d equal to V_sT, T is the brake reaction time, V_sIs the speed of the vehicle.

30. The safe distance calculation method according to claim 16, characterized in that: in step S3, a_t＝0，V_tIf Vs is 0 in the braking reaction time of the bicycle, the required safety distance is d (0-V)_s ²)/(2*a_s)；

If Vs is more than 0 in the braking reaction time of the self-vehicle, the required safety distance is

d＝V_s*T+1/2*a_s*T²+(0-(V_s+a_s*T)²)/(2*a_min)；

T is the brake reaction time, d is the required safety distance, V_sIs the speed of the bicycle, a_sIs the acceleration of the bicycle, a_tIs the target vehicle acceleration, V_tIs the target vehicle speed, a_minIs the maximum deceleration produced by wheel braking, in units: m/s²。

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