Semitrailer automatic emergency braking control system and control method based on vehicle-road cooperation

Abstract

The invention discloses a semitrailer automatic emergency braking control system and method based on vehicle-road cooperation. The system comprises an information acquisition module and a multi-stage AEB early warning module. The invention provides a semi-trailer braking control system, a multi-stage AEB braking module, an inverse braking module and a PID control module, and provides a braking control method using the control system, and accurate multi-stage early warning and multi-stage braking control are output for a semi-trailer under different road situations based on the vehicle-road cooperation technology. The brake deceleration output by the control strategy is converted into brake master cylinder pressure by constructing an inverse brake module; and based on a PID control module, the error between the ideal expected braking deceleration planned by the control strategy and the actual braking deceleration of the semi-trailer actually running under each working condition is reduced. The semitrailer can accurately judge and output accurate control braking deceleration according to different road scenes such as various road attachment conditions, and the requirement for automatic emergency braking control of the semitrailer under the complex road working conditions such as a low attachment road surface, a curve and a ramp is met.

Description

Technical Field

[0001] The present invention relates to the technical field of active safety control of road transport semi-trailers, and in particular to an automatic emergency braking control system and a control method for semi-trailers based on vehicle-road collaboration. Background Art

[0002] As an important vehicle in my country's freight industry, semi-trailers have irreplaceable transportation advantages over other semi-trailers. However, compared with ordinary passenger cars, semi-trailers are prone to collision accidents due to factors such as driver misjudgment, fatigue driving, and poor road adhesion conditions when driving at high speeds due to their high center of mass, long body, complex articulated structure, and large load capacity, resulting in serious property losses and casualties. In order to reduce the occurrence of such traffic accidents, intelligent transportation technology with collision avoidance as the core has developed rapidly. Precision braking is an integrated technology consisting of precise perception, precise decision-making, and precise execution. It is the basic condition for realizing autonomous driving and an important guarantee for the safe driving of vehicles.

[0003] However, the current research subjects and application objects of emergency braking systems are mostly passenger cars, and research on semi-trailers is still rare. In addition, existing AEB products on the market mostly rely on the vehicle's sensors for perception and longitudinal control. Since they cannot achieve precise braking control of semi-trailers according to different road conditions, their collision avoidance effects during actual operation still have a lot of room for improvement. Vehicle-road collaborative technology can provide information such as the precise position, slope, curve radius and even road adhesion coefficient of the target vehicle and the vehicle, which makes it possible to improve and enhance AEB performance.

[0004] To sum up, it is urgent to propose an automatic emergency braking control system based on vehicle-road collaborative technology and suitable for semi-trailers, so as to improve the driving safety of semi-trailers, help promote the advantages of "strip-and-hook transportation" and "section transportation", and explore the application practice of emergency braking systems in road transport vehicles in my country. Summary of the invention

[0005] The purpose of the present invention is to provide an automatic emergency braking control system for semi-trailers based on vehicle-road collaboration, so as to solve the limitations of the existing AEB control technology for semi-trailers in practical applications, such as insufficient human-machine integration and weak adaptability, especially in application scenarios such as low-adhesion roads, ramps, and curves, where the braking effect is poor or even fails. The invention aims to provide an effective method for improving the transportation safety of semi-trailers under complex road conditions.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] On the one hand, the present invention provides a semi-trailer automatic emergency braking control system based on vehicle-road collaboration, the control system comprising:

[0008] An information collection module is used to collect real-time road condition information of the semi-trailer using roadside unit equipment;

[0009] The multi-level AEB warning module is used to calculate the risk coefficient value based on the real-time road condition information and issue multi-level warnings to the semi-trailer according to the risk coefficient value;

[0010] The multi-level AEB braking module is used to obtain the expected braking deceleration value based on the safety distance model after the AEB braking of the semi-trailer is triggered, and input it into the braking system of the semi-trailer, so that the semi-trailer enters a slow braking or emergency braking state;

[0011] The reverse braking module is used to convert the desired braking deceleration output by the braking module into the brake master cylinder pressure to realize the braking control of the semi-trailer;

[0012] The PID control module is used to calculate the deceleration value error between the expected braking deceleration value of the semi-trailer and the actual braking deceleration value of the semi-trailer, and adjust the brake master cylinder pressure according to the deceleration value error to achieve error control.

[0013] Preferably, the multi-level AEB warning module calculates the risk coefficient value based on the real-time road condition information, including using a risk coefficient model to calculate the risk coefficient value, and the risk coefficient value RF calculation formula is as follows:

[0014]

[0015] Where S is the relative distance between vehicles, S w is the critical warning distance, and Sb is the critical braking distance.

[0016] Preferably, a multi-level warning is performed on the semi-trailer according to the risk coefficient value, including dividing the multi-level warning into four states of AEB state safety, first-level warning, second-level warning and AEB triggered braking according to different ranges of risk coefficient values ​​RF, and triggering the multi-level AEB braking module when AEB triggers braking;

[0017] Preferably, a multi-level safety distance model for a semitrailer under multiple road conditions is constructed in the multi-level AEB braking module, including a slow braking safety distance value and an emergency braking safety distance value. When AEB triggers braking, if the relative distance of the vehicle is less than the slow braking safety distance value, AEB triggers slow braking and obtains the corresponding expected braking deceleration value; when the relative distance of the vehicle is less than the emergency braking safety distance value, AEB triggers emergency braking and obtains the corresponding expected emergency braking deceleration value under the current road scene.

[0018] Preferably, the PID control module calculates the deceleration value error between the expected braking deceleration value and the braking deceleration value actually generated by the semi-trailer, and the braking deceleration value error er(t) is calculated by the following formula:

[0019] er(t)=y d (t)-y(t)

[0020] y d (t) is the desired control braking deceleration value;

[0021] y(t) is the actual braking deceleration value of the semitrailer.

[0022] On the other hand, the present invention also provides a method for controlling automatic emergency braking of a semitrailer based on vehicle-road collaboration, the control method adopts the above control system; the control method comprises the following steps:

[0023] S1 uses the roadside unit equipment to collect the real-time road condition information of the semi-trailer through the information collection module;

[0024] S2 calculates the risk coefficient value based on the real-time road condition information through the multi-level AEB warning module, issues multi-level warnings to the semi-trailer based on the risk coefficient value, and determines whether to trigger the AEB braking of the semi-trailer based on the risk coefficient;

[0025] S3 uses a multi-level AEB braking module to obtain the expected braking deceleration value based on the safety distance model after triggering the AEB braking of the semi-trailer, and inputs it into the braking system of the semi-trailer, so that the semi-trailer enters a slow braking or emergency braking state;

[0026] S4 converts the desired braking deceleration value output by the braking module into the brake master cylinder pressure of the semi-trailer through the reverse braking module, thereby realizing braking control of the semi-trailer;

[0027] S5 calculates the deceleration value error between the expected braking deceleration value and the actual braking deceleration value of the semi-trailer through the PID control module, and adjusts the brake master cylinder pressure according to the deceleration value error to reduce the deceleration value error.

[0028] Preferably, the multi-level warning is divided into four states: AEB status is safe, level one warning, level two warning and AEB triggered braking. No measures are taken when the AEB status is safe; when level one warning is taken, an image warning is performed; when level two warning is taken, a sound + image combined warning is performed; AEB triggered braking includes slow braking and emergency braking.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] The automatic emergency braking control system for a semitrailer based on vehicle-road collaboration provided by the present invention adopts a roadside unit device to collect real-time road condition information of the semitrailer; a multi-level AEB warning module is provided for calculating a risk coefficient value based on the real-time road condition information, and a multi-level warning is performed on the semitrailer according to the risk coefficient value, and whether the AEB braking of the semitrailer is triggered is determined through the multi-level warning; a multi-level AEB braking module is provided for obtaining an expected braking deceleration value based on a multi-level safety distance model after the AEB braking of the semitrailer is triggered, and inputting the value into the braking system of the semitrailer, so that the semitrailer enters a slow braking or emergency braking state; a reverse braking module is provided for converting the expected braking deceleration value output by the braking module into the pressure of the brake master cylinder of the semitrailer, so as to realize braking control of the semitrailer; a PID control module is provided for calculating the pressure difference between the expected braking deceleration value and the braking deceleration value actually generated by the semitrailer Deceleration value error, adjust the brake master cylinder pressure according to the deceleration value error to reduce the deceleration value error; the semi-trailer automatic emergency braking control system based on vehicle-road collaboration proposed in the present invention fully considers the limitations of existing semi-trailer braking control technology, that is, it mainly relies on the collision perception mechanism of TTC, the considerations are relatively simple, the application scenario is single, and it is difficult to meet the collision avoidance needs of semi-trailers under complex road conditions such as low-adhesion roads, curves, and ramps; accordingly, in order to solve the limitations of single-vehicle perception, based on vehicle-road collaboration technology, it is improved and optimized to establish a semi-trailer emergency braking control system suitable for multiple road scenarios; the invention solves the complexity problem of the semi-trailer dynamics control model, ensures that the semi-trailer has sufficient safe braking distance under various road conditions, effectively realizes vehicle collision avoidance, and provides important theoretical and technical support for improving the safety and reliability of the AEB system.

[0031] The automatic emergency braking control system for a semitrailer based on vehicle-road collaboration proposed in the present invention aims at the current situation that the research on braking systems is mainly focused on passenger cars. Combined with the important position of semitrailers in the field of transportation, a six-axle semitrailer is used as the research carrier. Taking into account the characteristics of the semitrailer itself such as large structural load and delayed control response of the braking system, an emergency braking control system suitable for the semitrailer is designed. This is of great significance for promoting the progress of the technical level of road transport vehicles in my country and improving its backward development. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 A schematic diagram of the structure of an automatic emergency braking control system for a semitrailer based on vehicle-road collaboration provided by the present invention;

[0033] Figure 2 This is the simulation test condition diagram of the semi-trailer in the road scene;

[0034] Figure 3 Schematic diagram of the reverse braking module in the automatic emergency braking control system for a semitrailer based on vehicle-road collaboration provided by the present invention;

[0035] Figure 4 This is the control system model diagram built in the joint simulation of TruckSim and Simulink;

[0036] Figure 5 The joint simulation results output by TruckSim and Simulink;

[0037] Figure 6 This is a schematic diagram of the actual braking deceleration curve of a semi-trailer without the PID control module;

[0038] Figure 7 This is a schematic diagram of the actual braking deceleration curve of a semi-trailer with a PID control module added;

[0039] Figure 8 A flow chart of the automatic emergency braking control method for a semitrailer based on vehicle-road collaboration provided by the present invention. DETAILED DESCRIPTION

[0040] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0041] Classic control strategy for semi-trailer:

[0042] The classic AEB control strategy for semi-trailers is defined based on the industry standard JT / T 1242-2019; the classic AEB system braking strategy is an emergency braking control strategy based on TTC, which usually refers to the time required for two vehicles to collide; during the operation of the semi-trailer, if the TTC is less than the threshold set by the system, the system will brake. The TTC calculation formula is as follows:

[0043]

[0044] Where D is the relative distance between the two vehicles, v r is the relative speed of the two vehicles

[0045] From this, the dangerous braking distance can be obtained:

[0046] d=TTC·v r +d0

[0047] Where d0 is the safety distance; the TTC threshold for the first braking of the classic AEB for semi-trailers is 2.5s, and the TTC threshold for the second braking is 1.2s; but because the classic control strategy is relatively simple and does not take into account factors such as the road environment, there are many problems in its actual use of semi-trailers: the above braking strategies or effects can only be achieved on high-adhesion roads, and according to the current industry average level, under ideal test conditions, semi-trailers can avoid collisions when traveling at a speed of about 50km / h, but when the speed exceeds this value, it is still difficult to avoid collisions with stationary targets. When the semi-trailer is on a low-adhesion road, it is difficult to achieve an ideal braking effect. And the classic AEB also performs poorly under complex working conditions: in curve scenes, ramp scenes, tunnel scenes, and ramp-low adhesion-tunnel combination scenes, the classic AEB cannot work normally or accurately.

[0048] The automatic emergency braking control system for a semitrailer based on vehicle-road collaboration provided by the present invention is as follows: Figure 1 As shown, including:

[0049] The information collection module is used to collect the real-time road condition information of the semi-trailer using the roadside unit equipment.

[0050] The real-time road condition information collected by the roadside unit is input to other modules of the control system through the Gauss-Krüger projection model;

[0051] Specifically, based on vehicle-road cooperative technology, the roadside unit (RSU) realizes V2I communication through the cellular network, and other modules of the control system transmit real-time road condition information, which includes the road adhesion coefficient, weather, curve curvature radius, ramp slope and relative position information of the semi-trailer. In V2X communication, the relative position information data sent by the roadside unit (RSU) adopts the WGS-84 international coordinate system (i.e., longitude and latitude). In order to facilitate the control system to obtain and process the real-time road condition information of the semi-trailer, the longitude and latitude need to be converted into the horizontal and vertical coordinates (x, y) in the plane rectangular Cartesian coordinate system through the Gauss-Krüger projection model. The specific conversion method is shown in equations (1) and (2):

[0052]

[0053] In formula (1) and formula (2), m = lcosB, l = L-L0, L is the longitude of the target position, B is the latitude of the target position, L0 is the longitude of the central meridian, t = tanB, η = e'cosB, X is the arc length of the meridian from the equator, the major axis of the earth is set to a, the minor axis is set to b, and e' is the second eccentricity of the ellipsoid

[0054] The multi-level AEB warning module is used to calculate the risk coefficient value based on the real-time road condition information, issue multi-level warnings to the semi-trailer based on the risk coefficient value, and determine whether to trigger the semi-trailer to brake based on its value;

[0055] Specifically, the multi-level AEB warning module calculates the risk coefficient value based on the real-time road condition information, including using a risk coefficient model to calculate the risk coefficient value. The risk coefficient value RF calculation formula is shown in formula (3):

[0056]

[0057] In formula (3), S is the relative distance between vehicles, S w is the critical warning distance, and Sb is the critical braking distance.

[0058] The relative distance S is the relative distance between the semi-trailer and the target obstacle, and the relative distance S is input by the sensor at the vehicle information input end.

[0059] Sb is the critical braking distance, that is, the distance when slow braking begins.

[0060] S w is the critical warning distance, and the relationship between the two is shown as follows (4):

[0061] S w =Sb+S0(4)

[0062] Where S0 is the distance traveled by the vehicle during the driver’s reaction time τ1.

[0063] The multi-level early warning control strategy designed based on RF value is as follows:

[0064]

[0065] The values ​​of τ1 and q will affect the intervention time of the multi-level warning. Based on industry standards, the following requirements are made for the multi-level warning and brake triggering time in the control system provided by the present invention:

[0066] 1) When the TTC of the semi-trailer is greater than 3s, the automatic emergency braking system cannot perform braking measures.

[0067] 2) When the TTC of the semi-trailer is greater than 4.4s, the automatic emergency braking system cannot take warning measures.

[0068] 3) The value of the braking trigger time minus the first-level warning trigger time should be greater than 1.4s, that is, the first-level warning trigger time should be issued 1.4s before the braking trigger time.

[0069] 4) The value of the braking trigger time minus the second-level warning trigger time should be greater than 0.8s, that is, the second-level warning trigger time should be issued 0.8s before the braking trigger time.

[0070] Taking into account the unique structural characteristics of the semi-trailer, based on a large number of simulation tests and result fitting, the key threshold values ​​are as follows:

[0071]

[0072] The multi-level warning and braking control is as follows:

[0073] 1) 1<RF, no action is taken;

[0074] 2) q<RF≤1, take the first-level warning, that is, the relative distance between the target semi-trailer and the target object is between the critical warning distance and the critical braking distance, and image warning is performed at this stage;

[0075] 3) 0<RF≤q, take the second-level warning, that is, the relative distance between the target semi-trailer and the target object is gradually approaching the critical braking distance, and a sound + image joint warning is performed at this stage;

[0076] 4) When RF≤0 and the relative distance between the vehicles (the distance between the semi-trailer and the obstacle) is less than the slow braking safety distance value, AEB triggers slow braking;

[0077] 5) When RF≤0 and the relative distance between the vehicles (the distance between the semi-trailer and the obstacle) is less than the emergency braking safety distance value, AEB triggers emergency braking.

[0078] Multi-level warnings are provided for semi-trailers according to the risk coefficient value, including dividing the multi-level warnings into four states: AEB state safety, first-level warning, second-level warning and AEB triggered braking according to different ranges of risk coefficient values;

[0079] The multi-level AEB braking module is used to obtain the expected braking deceleration value based on the safety distance model after the AEB braking of the semi-trailer is triggered, and input it into the braking system of the semi-trailer, so that the semi-trailer enters a slow braking or emergency braking state;

[0080] Specifically, the value of the semi-trailer's braking deceleration will have a great impact on the riding comfort of the passengers. If during the braking process, a small deceleration is first performed through slow braking, and then the braking intensity is increased to achieve collision avoidance of the semi-trailer, this can not only ensure riding comfort, but also avoid the occurrence of rear-end collisions. Therefore, the present invention divides the braking process of AEB into slow braking or emergency braking. The present invention takes into account the structural characteristics of the semi-trailer during the braking process, such as sway and vibration between the tractor and the trailer, the riding comfort of the driver and passengers when the semi-trailer brakes, and the guarantee of safe and reasonable lateral acceleration when the semi-trailer is driving under conditions such as bends. In the present invention, RF≤0, and when the relative distance between the vehicles (the distance between the semi-trailer and the obstacle) is less than the slow braking safety distance value, AEB triggers slow braking, and the braking deceleration value is controlled to be 3m / s 2 ; When RF≤0 and the relative distance between the vehicles (the distance between the semitrailer and the obstacle) is less than the emergency braking safety distance value, AEB triggers emergency braking, and the braking deceleration value is controlled to be the maximum braking deceleration value that the semitrailer can reach when driving on the road;

[0081] When the semi-trailer starts braking, in the AEB working stage, let the semi-trailer travel distance S1, which includes two parts. During the τ'2 time, the semi-trailer travels at a constant speed, and its travel distance is shown in formula (5):

[0082] S'1=v1·τ'2 (5)

[0083] In formula (5), v1 is the initial speed of the semitrailer when it starts braking;

[0084] τ1 is the driver's reaction time; due to the gap between the brake drum and the brake shoe, the time required for AEB to generate braking force is τ'2; the time for the pneumatic AEB braking force to increase is τ"2; τ3 is the duration of slow braking, and τ5 is the duration of emergency braking;

[0085] During the τ"2 time, the braking deceleration of the semitrailer increases linearly with time, that is, a1 is the slow braking deceleration;

[0086] The braking distance within τ"2 is calculated as shown in formula (6):

[0087]

[0088] S1 is the sum of S'1 and S"1, that is, S1 = S'1 + S"1;

[0089] v2 is the speed of the semitrailer after the first AEB action phase. From the above derivation, we can get:

[0090]

[0091] In the continuous braking stage, the semitrailer performs a uniform deceleration motion at a deceleration a1. The braking distance in this stage is shown in formula (7):

[0092]

[0093] In formula (6), v3 is 40 km / h, that is, the vehicle speed is reduced to 40 km / h through slow braking;

[0094] Since the AEB system is divided into two parts: slow braking and emergency braking, the AEB braking force growth time from a1 to the extreme value of braking deceleration is τ4. During the τ4 time, the braking deceleration of the semitrailer increases linearly with the increase of time, that is, a1 is the deceleration of slow braking, which is 3m / s 2 , a2 is the maximum deceleration of the semitrailer under the road conditions;

[0095] The braking distance within τ4 time is calculated as shown in formula (8):

[0096]

[0097] v4 is the speed of the semitrailer after the second AEB action phase;

[0098] From the above derivation, we can get:

[0099]

[0100] In the continuous braking stage, the semitrailer performs a uniform deceleration motion at a deceleration a2. The braking distance in this stage is as shown in formula (9):

[0101]

[0102] Where v5 is 0km / h;

[0103] The safety distance d0 is the relative distance between the semitrailer in front and the vehicle when the semitrailer escapes the danger of collision, that is, the relative speed with the front vehicle is 0 or the vehicle is stopped. Considering the influence of road environment, weather and road adhesion coefficient on braking distance, the value is 3m; v1 is the initial speed of the semitrailer when braking, v2 is the speed of the semitrailer after the first AEB action stage, v3 is 40km / h, v4 is the speed of the semitrailer after the second AEB action stage, v5 is 0km / h, τ'2 is the time for AEB to overcome the empty travel, because the semitrailer is pneumatic brake, the value is 0.05s, τ"2 is the time required for the braking deceleration to increase from 0 to the slow braking deceleration, which is 0.2s, τ4 is the time required for the slow braking deceleration a1 to increase to the deceleration extreme value, which is 0.16s. Because the unit of vehicle speed is km / h, unit conversion is required in actual calculation and programming.

[0104] In summary, the overall semi-trailer safety braking distance model is shown in formula (10):

[0105]

[0106] Due to τ2" 2 and The value of is small, so and To omit;

[0107] When the road ahead is straight:

[0108] The calculation formula of the slow braking trigger distance is shown in formula (11):

[0109]

[0110] The calculation formula of emergency braking trigger distance is shown in formula (12):

[0111]

[0112] When the road ahead is curved:

[0113] The calculation formula of the slow braking trigger distance is shown in formula (13):

[0114]

[0115] The calculation formula of emergency braking trigger distance is shown in formula (14):

[0116]

[0117] Where: R is the curvature radius of the curved road;

[0118] When the road ahead is a slope:

[0119] The calculation formula of the slow braking trigger distance is shown in formula (15):

[0120]

[0121] The calculation formula of emergency braking trigger distance is shown in formula (16):

[0122]

[0123] In formula (16): i represents the slope of the ramp;

[0124] Method for obtaining the maximum braking deceleration value that a semi-trailer can achieve when traveling on the road: obtain the maximum braking deceleration value that a semi-trailer can achieve under various road conditions and preset it in the multi-level AEB braking module in advance, match the corresponding road conditions according to the real-time road condition information of the current semi-trailer, and thereby obtain the maximum braking deceleration value that the semi-trailer can achieve under the road condition, that is, the control braking deceleration value obtained by the multi-level AEB braking module when AEB triggers emergency braking;

[0125] From the above analysis, it can be seen that if RF≤0, the multi-level warning is in the AEB trigger braking state, then it is determined that the semi-trailer needs to be braked; the multi-level safety distance model is preset in the multi-level AEB braking module;

[0126] When RF≤0, and the relative distance between the vehicles (the distance between the semi-trailer and the obstacle) is less than the slow braking safety distance value, AEB triggers slow braking;

[0127] When RF≤0 and the relative distance between the vehicles (the distance between the semi-trailer and the obstacle) is less than the emergency braking safety distance value, AEB triggers emergency braking.

[0128] The control system provided by the present invention describes the warning and braking of the semi-trailer, uses the risk coefficient as the standard for multi-level warning triggering, and then controls the multi-level braking of the semi-trailer by constructing a safety distance model for different road conditions after the risk coefficient value of the braking triggering is met. The multi-level AEB braking module obtains the AEB output expected braking deceleration value for the semi-trailer according to the preset slow braking safety distance value and emergency braking safety distance value to control the braking of the semi-trailer.

[0129] The reverse braking module is used to convert the desired braking deceleration value input into the braking system of the semi-trailer into the brake master cylinder pressure to realize automatic emergency braking control of the semi-trailer.

[0130] Since ordinary cars use hydraulic braking systems, the ratio K between the oil circuit pressure and the brake pressure in their braking systems is a constant, and the braking force is approximately linearly related to the brake oil circuit pressure; however, in pneumatic braking systems, this ratio is not fixed, and the braking force is nonlinearly related to the air pressure; semi-trailers use pneumatic braking, which is significantly different from the braking system of passenger cars; the AEB control strategy achieves effective control of the braking process by transmitting the expected deceleration to the semi-trailer dynamics model. Since the semi-trailer uses a pneumatic braking system, the dynamics model structure is complex, and it is difficult to directly control the running state of the semi-trailer through the expected deceleration. Therefore, the regression analysis method is introduced. Through the TruckSim simulation software, the running stability of the semi-trailer during the braking process is fully considered. In view of the characteristics of the center of gravity offset, sway and vibration between the tractor and the semi-trailer during the braking process, a large number of simulation tests are carried out under different adhesion coefficients, curve curvatures and slopes. The simulation test conditions are as follows Figure 2 As shown in the figure, the test results are input into the Lookup Table (2-D) module of Simulink to complete the construction of the reverse braking module suitable for semi-trailers under various road conditions, and realize the accurate conversion of braking deceleration to brake master cylinder pressure. The schematic diagram of the reverse braking module is shown in Figure 3 shown.

[0131] The PID control module is used to calculate the deceleration value error between the expected braking deceleration value and the braking deceleration value actually generated by the semi-trailer, and adjust the brake master cylinder pressure according to the deceleration value error to reduce the deceleration value error.

[0132] The deceleration value error between the expected braking deceleration value and the actual braking deceleration value of the semi-trailer is calculated in the PID control module. The calculation formula of the braking deceleration value error er(t) is shown in formula (17):

[0133] er(t)=y d (t)-y(t)(17)

[0134] y d (t) is the control braking deceleration value;

[0135] y(t) is the actual braking deceleration value of the semitrailer.

[0136] Its control law is shown in formula (18):

[0137]

[0138] Its transfer function is shown in formula (19):

[0139]

[0140] In the above formula, k pis the proportionality coefficient, T i is the integration time constant, T d is the differential time constant, and all three are adjustable parameters. The present invention fully considers the running stability and structural characteristics of the semi-trailer, and determines the optimal control parameter values ​​under different road conditions through simulation trial and error method:

[0141]

[0142] The PID control module corrects the error between the actual braking deceleration of the semitrailer and the ideal braking deceleration under the braking pressure output by the reverse braking module. The PID control is essentially to directly correct the braking pressure so that the actual deceleration of the semitrailer is close to the ideal deceleration. The present invention fully considers the running stability and structural characteristics of the semitrailer, and determines the optimal control parameter values ​​under different road scenarios through simulation trial and error. Figure 6 This is a schematic diagram of the actual braking deceleration curve of a semi-trailer without the PID control module. Figure 7 This is a schematic diagram of the actual braking deceleration curve of the semi-trailer with the PID control module added. Figure 6 and Figure 7 It can be seen that the PID control module has effectively reduced the hysteresis time of the semi-trailer during braking and achieved braking control more quickly. The actual braking deceleration of the AEB system is closer to the controlled braking deceleration value given by the control system. The braking deceleration in each stage tends to be linear as a whole, with a smaller variation range, and the result is more ideal.

[0143] The present invention also provides a semi-trailer automatic emergency braking control method based on vehicle-road collaboration, the control method is the above-mentioned semi-trailer automatic emergency braking control system based on vehicle-road collaboration; the control method comprises the following steps:

[0144] S1 uses the roadside unit equipment to collect the real-time road condition information of the semi-trailer through the information collection module;

[0145] S2 calculates the risk coefficient value based on the real-time road condition information through the multi-level AEB warning module, issues multi-level warnings to the semi-trailer based on the risk coefficient value, and determines whether to trigger the AEB braking of the semi-trailer based on the risk coefficient;

[0146] S3 uses the multi-level AEB braking module to obtain the desired control braking deceleration value based on the multi-level safety distance model after triggering the AEB braking of the semi-trailer, and inputs it into the braking system of the semi-trailer, so that the semi-trailer enters a slow braking or emergency braking state;

[0147] S4 converts the desired control braking deceleration value input to AEB into the brake master cylinder pressure through the reverse braking module to achieve automatic emergency braking control of the semi-trailer;

[0148] S5 calculates the deceleration value error between the expected braking deceleration value and the actual braking deceleration value of the semi-trailer through the PID control module, and adjusts the brake master cylinder pressure according to the deceleration value error to reduce the deceleration value error.

[0149] Preferably, the multi-level warning is divided into four states: AEB status is safe, level one warning, level two warning and AEB triggered braking. No measures are taken when the AEB status is safe; when level one warning is taken, an image warning is performed; when level two warning is taken, a sound + image combined warning is performed; AEB triggered braking includes slow braking and emergency braking.

[0150] The semi-trailer automatic emergency braking control system based on vehicle-road collaboration provided by the present invention is jointly simulated by TruckSim and Simulink to verify the effectiveness of the control system;

[0151] Specifically, a six-axle semi-trailer is used as the research vehicle, and the semi-trailer vehicle model and road condition model are constructed in TruckSim: including the vehicle body length, width, height, curb weight, the size and center of mass position of the loaded cargo, mass parameters, wheelbase, tire radius, moment of inertia, etc., to ensure that the simulation results are more accurate and effective; then the semi-trailer is modeled in various modules, including aerodynamics, transmission system, steering system, driving system and braking system; according to the highway route design specification JTG D20-2006 requires that parameters such as road path, road adhesion coefficient, slope, and curve curvature radius be set in TruckSim; in order to meet the requirements of highway route design specifications, the road superelevation should be set in the curve working condition modeling: when the road adhesion coefficient is high, the superelevation should be set to 10%; when the adhesion coefficient is low, such as in snowy and icy conditions, the superelevation needs to be adjusted to 6%; the semi-trailer automatic emergency braking control system based on vehicle-road collaboration is built in Simulink. The control system includes the following modules: multi-level AEB warning module, multi-level AEB braking module, reverse braking model module, PID control module, and result display module; through debugging, each module works together to ensure the accuracy of the braking process and the effectiveness of the system response. The control system built is as follows: Figure 4 As shown in the figure, the interface connection between the two systems is completed, a closed-loop system is formed between the two softwares, and the joint simulation verification of the strategy model is carried out and the simulation results of the two control strategies are compared: Based on the AEB test specification, the front vehicle static condition is designed, and the semi-trailer is allowed to perform braking simulations under straight roads, slopes, curves and other conditions with different road adhesion coefficients, as shown in the figure. Figure 5As shown in the figure, the joint simulation results of safe vehicle distance during parking, self-vehicle warning and braking trigger signal, relative distance between two vehicles, self-vehicle speed, self-vehicle braking deceleration, self-vehicle lateral acceleration, etc. are output respectively. The results show that compared with the classic control strategy of semi-trailer, the improved control strategy can ensure sufficient safe braking distance under the above working conditions, effectively realize semi-trailer collision avoidance, and significantly improve the safety and reliability of the AEB system.

[0152] The present invention fully considers the limitations of the classic semi-trailer emergency braking control strategy, and is based on the vehicle-road collaborative technology to improve and optimize it: first, the real-time road condition information collected by the roadside unit equipment is transmitted to the semi-trailer through Gauss-Krüger projection; then, based on the road condition information and the structural characteristics of the semi-trailer itself, the semi-trailer plans the optimal triggering time of the braking control system in multiple scenarios, and establishes a multi-level braking control strategy model suitable for the semi-trailer; and designs a multi-level early warning control strategy for the semi-trailer, clarifying the control parameters of the multi-level early warning system under different road adhesion conditions and road types and the early warning key thresholds corresponding to various road conditions. Next, considering the difference in braking mechanism between semi-trailers and ordinary passenger cars, taking into account the operational stability of the braking process of semi-trailers, the braking deceleration output by the control strategy is converted into the brake master cylinder pressure by constructing a reverse braking model for semi-trailers; developing a PID controller that meets the braking requirements of semi-trailers, and defining the optimal control parameter values ​​under different road conditions, thereby reducing the error between the ideal expected braking deceleration planned by the control strategy and the actual braking deceleration of the semi-trailer under various conditions; combining the above parts to complete the construction of the semi-trailer automatic emergency braking control strategy based on vehicle-road collaboration; finally, a joint simulation is performed to verify the effectiveness of the semi-trailer automatic emergency braking control strategy based on vehicle-road collaboration. The present invention solves the limitations of the semi-trailer AEB classic control strategy in practical applications, such as insufficient human-machine integration and weak adaptability, especially in application scenarios such as low-adhesion roads, ramps, and curves, where the braking effect is poor or even fails, providing important theoretical and technical support for improving the driving safety of semi-trailers and improving the reliability of emergency braking systems.

[0153] The automatic emergency braking control system and method for semi-trailers based on vehicle-road collaboration proposed in the present invention fully consider the limitations of the classic braking control strategy of semi-trailers and establish an emergency braking control strategy for semi-trailers applicable to multiple road conditions. The invention solves the complexity problem of the semi-trailer dynamic control model, ensures that the semi-trailer has sufficient safe braking distance under multiple road conditions, effectively realizes semi-trailer collision avoidance, and provides important theoretical and technical support for improving the safety and reliability of AEB systems.

[0154] The automatic emergency braking control method for a semitrailer based on vehicle-road collaboration proposed in the present invention aims at the current situation that the research on braking systems is mainly focused on passenger cars. Combined with the important position of semitrailers in the field of transportation, a six-axle semitrailer is used as the research carrier. Taking into account the characteristics of the semitrailer itself such as large structural load and delayed control response of the braking system, an emergency braking control strategy suitable for the semitrailer is designed. This is of great significance for promoting the advancement of the technical level of road transport semitrailers in my country and improving their backward development.

Claims

1. The automatic emergency braking control system for semi-trailers based on vehicle-road collaboration is characterized by: The control system includes: The information acquisition module is used to transmit the road condition information to the semi-trailer, and obtain the parameters such as the road adhesion coefficient, the curve curvature radius, the ramp gradient, etc. used for model input, as well as the position relationship relative to the semi-trailer through Gauss-Krüger projection; The multi-level AEB warning module is used to calculate the risk coefficient value based on real-time road condition information and control the multi-level warning of the semi-trailer according to the risk coefficient value; The multi-level AEB braking module is used to obtain the expected braking deceleration value based on the safety distance model under different working conditions after the AEB braking of the semi-trailer is triggered, and input it into the braking system of the semi-trailer, so that the semi-trailer enters a slow braking or emergency braking state; The reverse braking module is used to convert the braking deceleration output by the multi-stage AEB braking module into the brake master cylinder pressure to achieve braking control of the vehicle; The PID control module is used to calculate the error between the expected deceleration value output by the brake module and the actual braking deceleration value generated by the semi-trailer, and adjust the brake master cylinder pressure according to the deceleration value error to achieve error control.

2. The automatic emergency braking control system for a semitrailer based on vehicle-road collaboration according to claim 1 is characterized in that: The multi-level AEB warning module calculates the risk coefficient value based on the real-time road condition information, including using the risk coefficient model to calculate the risk coefficient value. The risk coefficient value RF calculation formula is shown in formula (3): Where S is the relative distance between vehicles, S w is the critical warning distance, and Sb is the critical braking distance.

3. The automatic emergency braking control system for a semitrailer based on vehicle-road collaboration according to claim 1 is characterized in that: Multi-level warning is given to the semi-trailer according to the risk coefficient value, including dividing the multi-level warning into four states: AEB state safety, level one warning, level two warning and AEB triggered braking according to different ranges of risk coefficient values ​​RF. When AEB triggers braking, the multi-level AEB braking module is triggered.

4. The automatic emergency braking control system for a semitrailer based on vehicle-road collaboration according to claim 1 is characterized in that: A multi-level safety distance model for semi-trailers is constructed in the multi-level AEB braking module, including the deceleration and braking distances and emergency braking distances under various road conditions. The expected braking deceleration is output by comparing the relative distance between the vehicle and the obstacle target with the deceleration and braking distance values ​​and the emergency braking distance values.

5. The automatic emergency braking control system for a semitrailer based on vehicle-road collaboration according to claim 1 is characterized in that: The deceleration value error between the expected braking deceleration value and the actual braking deceleration value of the semi-trailer is calculated in the PID control module. The calculation formula of the braking deceleration value error er(t) is shown in formula (17): er(t)=y d (t)-y(t) (17) y d (t) is the desired control deceleration value; y(t) is the actual braking deceleration value of the semitrailer.

6. The automatic emergency braking control method for a semitrailer based on vehicle-road collaboration is characterized in that: The control method adopts the control system as described in any one of claims 1 to 5; the control method comprises the following steps: S1 uses the roadside unit equipment to collect the real-time road condition information of the semi-trailer through the information collection module; S2 calculates the risk coefficient value based on the real-time road condition information through the multi-level AEB warning module, issues multi-level warnings to the semi-trailer based on the risk coefficient value, and determines whether to trigger the AEB braking of the semi-trailer based on the risk coefficient; S3 uses a multi-level AEB braking module to obtain the desired control braking deceleration value based on the safety distance model after triggering the AEB braking of the semi-trailer, and inputs it into the braking system of the semi-trailer, so that the semi-trailer enters a slow braking or emergency braking state; S4 converts the desired braking deceleration output by the braking module into the pressure of the semi-trailer brake master cylinder through the reverse braking module to achieve vehicle braking control. S5 calculates the deceleration value error between the expected braking deceleration value and the actual braking deceleration value of the semi-trailer through the PID control module, and adjusts the brake master cylinder pressure according to the deceleration value error to reduce the deceleration value error.

7. The method for controlling automatic emergency braking of a semitrailer based on vehicle-road collaboration according to claim 6 is characterized in that: The multi-level warning is divided into four states: AEB status is safe, level one warning, level two warning and AEB triggered braking. No measures are taken when the AEB status is safe; when level one warning is taken, an image warning is given; when level two warning is taken, a sound + image combined warning is given; AEB triggered braking includes slow braking and emergency braking.

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