Control methods, devices, and storage media based on braking process considering the coefficient of adhesion

Abstract

This invention discloses a braking control method, device, and storage medium that considers the real-time coefficient of adhesion. First, vehicle and road information is acquired through inter-vehicle communication and sensor devices. Then, based on this information, a safe distance model considering the coefficient of adhesion and based on the braking process is constructed. Finally, based on this model, the speed of the following vehicle is adjusted according to the braking control method. This invention designs a safe distance model considering the coefficient of adhesion and based on the braking process, solving the problem that Berkeley safe distance ignores the impact of changes in the road surface adhesion coefficient during braking on the braking distance; ensuring the stability of convoy following and the safety of the following vehicle in scenarios where the preceding vehicle brakes suddenly. This invention compares the proposed safe distance model with the Berkeley safe distance model to verify the accuracy of the calculated safe distance; finally, a convoy following scenario is simulated to verify the model's safety and stability.

Description

Technical Field

[0001] This invention belongs to the field of automotive safety technology, specifically the field of car following, and more specifically, it relates to a braking control method, device, and storage medium that considers the real-time adhesion coefficient. Background Technology

[0002] Car-following models are among the most common micro-traffic flow models, and research on car-following behavior is a hot topic both domestically and internationally. Common car-following models include data-driven models, stimulus-response models, physiological-psychological models, and safety distance models. Traditional safety distance models fall into three categories: safety distance models based on headway, safety distance models based on the braking process, and safety distance models based on the driver. Safety distance models based on the braking process can ensure vehicle safety in emergency braking scenarios involving the vehicle ahead. Many safety distance models use stopping distance when calculating safety distance. One problem with stopping distance is that it only considers the vehicle's final position. Therefore, it cannot guarantee the safety of the entire braking process. The Berkeley safety distance model is a traditional safety distance model that uses stopping distance to calculate safety distance.

[0003] Driving safety distance is closely related to the vehicle braking process. Road surface type is one of the most important factors affecting braking distance, as different types of road surfaces have different coefficients of adhesion. Traditional safety distance models, such as the Berkeley safety distance model, assume that the coefficient of adhesion is constant. However, in reality, the coefficient of adhesion changes with various factors, such as slippery surfaces, standing water, snow or ice, or oil stains. Ignoring changes in the coefficient of adhesion during braking may lead to the following adverse results: 1) When the coefficient of adhesion changes, the braking distance will be affected. If the model ignores this change, the calculated braking distance will be inaccurate. This may result in insufficient estimated braking distance, preventing the vehicle from stopping in time and increasing the risk of collision. 2) On roads with low coefficients of adhesion, vehicles may skid or drift. If the driver does not have sufficient braking distance to adapt to this change, the vehicle may not be able to stop accurately, easily leading to loss of control and accidents.

[0004] Although some existing models consider vehicle control methods on roads with different road surface adhesion coefficients, these models do not fully account for the impact of real-time changes in road surface adhesion coefficients on safe distances, making it difficult to adapt to road traffic environments with varying road surface adhesion coefficients. Summary of the Invention

[0005] The purpose of this invention is to provide a braking control method that considers the real-time coefficient of adhesion, solving the problem that the Berkeley safety distance ignores the impact of changes in the road surface coefficient of adhesion during braking on the braking distance, and ensuring the safety of the following vehicle throughout the braking process in scenarios where the preceding vehicle brakes suddenly. This invention first acquires real-time vehicle and road information through vehicle-to-vehicle communication and sensor devices; then, it constructs a safety distance model based on the braking process that considers the road surface coefficient of adhesion, calculates the braking distance by combining the real-time changes in the road surface coefficient of adhesion, thereby determining the safe distance between the following and preceding vehicles; based on the constructed safety distance model, the speed of the following vehicle is adjusted according to the braking control method to ensure the driving safety of the following vehicle. To achieve the above objective, this invention adopts the following technical solution: A braking control method considering the real-time coefficient of adhesion includes the following steps:

[0006] Step 1: Obtain information on the road surface adhesion coefficient of each road segment, the coordinates of each vehicle at each time, and the speed information of each vehicle at each time through vehicle-to-vehicle communication and sensor equipment.

[0007] Step 2: Based on vehicle and road information, construct a safe distance model based on the braking process that considers the coefficient of adhesion;

[0008] Step 3: Based on the safe distance model constructed in Step 2, adjust the speed of the following vehicle according to the braking control method;

[0009] Step 4: Compare the safety distance model based on the braking process that considers the adhesion coefficient with the Berkeley safety distance model to verify the accuracy of the safety distance calculated by the safety distance model based on the braking process that considers the adhesion coefficient.

[0010] Step 5: Simulate a convoy following scenario to verify the safety and stability of the safety distance model based on the braking process, which takes into account the adhesion coefficient.

[0011] Furthermore, the specific implementation steps of step 2 are as follows:

[0012] Step 2.1: Assume that at time st, car n (vehicle number n) brakes with maximum deceleration until it comes to a stop, and the road segment where the car is located is different at the beginning and end of the braking process. Determine the road segment number si where car n is located at the beginning and end of the braking process. n,st and ei n,st .

[0013] The si can be determined simply by comparing the coordinates of the start and end points of each road segment. n,st The si n,st The number of the road segment where car n is located at the start of the braking process is shown in the following formula:

[0014]

[0015] In the formula, For road section si n,st The starting coordinates, For road section si n,st The endpoint coordinates.

[0016] ei n,st Ei represents the road segment number where car n begins braking at time st until braking ends (speed drops to zero). n,st The calculation is shown in the following formula:

[0017]

[0018]

[0019] In the formula, v n,st,i Let x be the starting point of car n on road segment i. i The velocity at that point, μ i Let x be the road surface adhesion coefficient of road segment i. i Let x be the starting coordinate of road segment i. i+1 Let x be the coordinates of the end point of road segment i. n (st) represents the coordinates of car n at time st, x′ n (st) represents the speed of car n at time st;

[0020] Step 2.2: Calculate when car n starts braking at time st to reach x. i At time t n,st,i and the moment when braking ends et n,st As shown in the following formula:

[0021]

[0022]

[0023] In the formula, x′ n (st) represents the speed of car n at time st. For road section ei n,st The road surface adhesion coefficient, Let car n begin braking at time st to reach road segment ei. n,st The velocity at the starting point;

[0024] Step 2.3: Calculate the distance S traveled by the car from time st until time t when braking begins. n,st,t As shown in the following formula:

[0025]

[0026] In the formula, For road section si n,st The road surface adhesion coefficient, For road section ei n,st The starting coordinates, Let car n begin braking at time st to reach road segment ei. n,st At the starting point, under condition t n,st,i <t≤t n,st,i+1 The range of i in the equation is i = si. n,st +1,si n,st +2,...,ei n,st -1;

[0027] Step 2.4: Assume that at time st, the preceding vehicle brakes suddenly with maximum deceleration until it stops; the following vehicle first moves at a constant speed for a duration of reaction time τ, and then brakes with maximum deceleration until it stops. Calculate the distance Srb traveled by the following vehicle from time st to time t. n,st,t As shown in the following formula:

[0028]

[0029] In the formula, S n,st+τ,t Let n be the distance traveled by car n from time st+τ until time t;

[0030] Step 2.5: Calculate the minimum safe distance SDmin based on the braking process, considering the adhesion coefficient, as proposed in this paper. n+1 (t), as shown in the following formula:

[0031] SDmin n+1 (t)=max(Srb n+1,t,element -S n,t,element ,0)+L n +d

[0032] In the formula, Srb n+1,t,element Let S be the distance traveled by car n+1 starting from time t, initially moving at a constant speed for one reaction time, then braking until time element. n,t,element Let L be the distance traveled by car n from time t when it starts braking until time element. n Let n be the length of the car, d be the stationary safety distance, and the range of values ​​for element is shown in the following formula:

[0033] element∈{t+τ,et n,t ,et n+1,t+τ}∪{t n,t,i |i=si n,t +1,si n,t +2,…,ei n,t}∪{t n+1,t+τ,i |i=sin+1,t+τ +1,si n+1,t+τ +2,...,ei n+1,t+τ}

[0034] Step 2.6: Calculate the expected safety distance SDexp n+1 (t) and maximum safe distance SDmax n+1 (t), as shown in the following formula:

[0035] SDexp n+1 (t)=SDmin n+1 (t)+x′ n+1 (t)*τ

[0036] SDmax n+1 (t)=SDexp n+1 (t)+V*τ

[0037] In the formula, V is the maximum permissible speed on the road, and x′ n+1 (t) represents the speed of car n+1 at time t.

[0038] Furthermore, the specific implementation steps of step 3 are as follows:

[0039] Adjust the speed of the following vehicle according to the braking control method, and the acceleration a of the following vehicle at time t+τ. n+1 (t+τ), as shown in the following equation:

[0040]

[0041] In the formula, a n+1 (t+τ) represents the acceleration of car number n+1 at time t+τ, x n+1 (t+τ) represents the position of car n+1 at time t+τ, μ(x) n+1 (t+τ) represents x n+1 The road adhesion coefficient at coordinate (t+τ), g is the acceleration due to gravity, -μ(x n+1 (t+τ))*g is the expression at x n+1 The maximum deceleration at the (t+τ) coordinate is Δx. n (t) represents the distance between car n and car n+1 at time t, SDmin n+1 (t), SDexp n+1 (t) and SDmax n+1 (t) represents the minimum safe distance, expected safe distance, and maximum safe distance based on the braking process, considering the adhesion coefficient; α is the adjustment coefficient; τ is the reaction time; and C n+1 For the maximum comfort acceleration of the car at n+1, the step function s(u) is shown in the following equation:

[0042]

[0043] Furthermore, the specific implementation steps of step 4 are as follows:

[0044] Step 4.1: Simulate the scenario where the road surface adhesion coefficient changes from μ0 to μ1 during vehicle braking, and calculate the minimum safe distance and Berkeley safe distance based on the braking process, taking into account the adhesion coefficient.

[0045] Step 4.2: Analyze the impact of changes in road surface adhesion coefficient on the minimum safe distance and Berkeley safe distance based on the braking process, taking adhesion coefficient into account;

[0046] Step 4.3: Compare the minimum safe distance based on the braking process, which takes into account the coefficient of adhesion, with the Berkeley safe distance, and analyze the differences between the two.

[0047] Furthermore, the specific implementation steps of step 5 are as follows:

[0048] Step 5.1: At the initial moment, all cars in the convoy are stationary and maintain a certain distance between adjacent cars. The lead car first accelerates uniformly, then moves at a constant speed, and finally decelerates uniformly until it stops. The following cars in the convoy move according to the braking control method. The following process of the convoy in the three stages of starting, moving at a constant speed and stopping is simulated.

[0049] Step 5.2: Analyze the stability of the convoy following process;

[0050] Step 5.3: Analyze the safety of the convoy following process.

[0051] The present invention also provides a control device based on the braking process that takes into account the coefficient of adhesion, comprising:

[0052] The information acquisition unit acquires information on the changes in road surface adhesion coefficient, the coordinates of each vehicle at each moment, and the speed information of each vehicle at each moment in real time through inter-vehicle communication and sensor equipment.

[0053] Based on vehicle and road information, a safe distance model based on the braking process is constructed, taking into account the adhesion coefficient.

[0054] The adjustment unit adjusts the speed of the following vehicle according to the braking control method, based on the constructed safe distance model.

[0055] The accuracy verification unit compares the safety distance model based on the braking process, which considers the adhesion coefficient, with the Berkeley safety distance model to verify the accuracy of the safety distance calculated by the safety distance model based on the braking process, which considers the adhesion coefficient.

[0056] To verify the safety unit, a simulated convoy following scenario was used to verify the safety and stability of the safety distance model based on the braking process, which takes into account the adhesion coefficient.

[0057] The present invention also provides a braking process-based control system that takes into account the coefficient of adhesion, the system including a processor and a memory, the processor executing computer instructions stored in the memory to implement the above method.

[0058] The present invention also provides a computer-readable storage medium for storing non-transitory computer-readable instructions that, when executed by a computer, cause the computer to perform the method.

[0059] This invention designs a safety distance model based on the braking process that considers the coefficient of friction, solving the problem that Berkeley safety distance ignores the impact of changes in the road surface coefficient of friction during braking on the braking distance. Based on the safety distance model based on the braking process that considers the coefficient of friction, the speed of the following vehicle is adjusted through braking control methods to ensure the stability of the convoy following process and to ensure the safety of the following vehicle throughout the braking process in scenarios where the preceding vehicle brakes suddenly. Attached Figure Description

[0060] Figure 1 This is a flowchart upon which the braking control method considering the real-time adhesion coefficient of the present invention is based;

[0061] Figure 2 This is a diagram illustrating the calculated Berkeley safety distance;

[0062] Figure 3 This is a schematic diagram of the minimum safe distance based on the braking process, which takes into account the adhesion coefficient, calculated by the braking control method of the present invention.

[0063] Figure 4 This is a schematic diagram showing the difference between the calculated Berkeley safe distance and the minimum safe distance based on the braking process, taking into account the adhesion coefficient;

[0064] Figure 5 This is a diagram of the braking process of a following vehicle in the Berkeley safety distance model and the proposed safety distance model;

[0065] Figure 6 This invention provides a braking control method that considers the real-time adhesion coefficient, and a speed diagram of the convoy following process.

[0066] Figure 7 This invention provides a braking control method that considers real-time adhesion coefficients, including a diagram showing the vehicle spacing during convoy following.

[0067] Figure 8This is a graph showing the ratio of the actual distance between convoys during the following process to the minimum safe distance based on the braking process, taking into account the adhesion coefficient, in a braking control method that considers the real-time adhesion coefficient according to the present invention. Detailed Implementation

[0068] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0069] See appendix Figure 1 This invention discloses a braking control method considering real-time adhesion coefficient, specifically including the following steps: Step 1: Obtain road surface adhesion coefficient information for each road segment, the coordinates of each vehicle at each moment, and the speed information of each vehicle through sensor devices and vehicle-to-vehicle communication. Specifically, the road surface adhesion coefficient sensor device and data analysis technology are used to detect the road surface's slipperiness, water accumulation, temperature changes, etc., to obtain the road surface adhesion coefficient information in real time; vehicle-mounted sensors and the Global Positioning System (GPS) are used to measure and monitor vehicle speed, coordinates, and other information, and vehicle-to-vehicle communication technologies such as 5G-V2X and DSRC are used to achieve real-time information exchange and communication between vehicles. The road surface adhesion coefficient refers to the friction coefficient between the vehicle tires and the road surface, ranging from 0 to 1. The higher the road surface adhesion coefficient, the better the vehicle's grip and the shorter the braking distance; the higher the vehicle speed, the longer the braking time and the longer the braking distance; the distance between vehicles can be calculated using vehicle coordinates, and the greater the distance between vehicles, the safer the vehicle. Incorporating the road surface adhesion coefficient, vehicle speed, and vehicle coordinates into the braking control method helps to adjust the safe distance between vehicles based on road conditions and vehicle speed.

[0070] The braking control method considering the real-time adhesion coefficient disclosed in this invention further includes step 2: constructing a safe distance model for braking control considering the adhesion coefficient based on the obtained information on the change of road surface adhesion coefficient of each road segment, the coordinates of each vehicle at each time, and the speed information of each vehicle.

[0071] The specific steps of step 2 are as follows:

[0072] Step 2.1: Assume that at time st, car n (referring to car number n) brakes with maximum deceleration until it stops, and the road segment where the car is located is different at the beginning and end of the braking process;

[0073] The road segment where car n is located at the start of the braking process is numbered as si. n,st The road segment number where car n is located at the end of the braking process is determined to be ei. n,st ;

[0074] By comparing the starting and ending coordinates of each road segment, si can be determined. n,st The si n,stThe number of the road segment where car n is located at the start of the braking process is shown in the following formula:

[0075]

[0076] In the formula, For road section si n,st The starting coordinates, For road section si n,st The endpoint coordinates;

[0077] ei n,st Ei represents the road segment number where car n begins braking at time st until braking ends (when the speed drops to zero). n,st The calculation is shown in the following formula:

[0078]

[0079]

[0080] In the formula, v n,st,i Let car n start braking at time st to reach the starting point x of road segment i. i The velocity at that point, g is the acceleration due to gravity, μ i Let x be the road surface adhesion coefficient of road segment i. i Let x be the starting coordinate of road segment i. i+1 Let x be the coordinates of the end point of road segment i. n (st) represents the coordinates of car n at time st, x′ n (st) represents the speed of car n at time st;

[0081] Step 2.2: Calculate when car n starts braking at time st to reach x. i At time t n,st,i and the moment when braking ends et n,st As shown in the following formula:

[0082]

[0083]

[0084] In the formula, x′ n (st) represents the speed of car n at time st. For road section ei n,st The road surface adhesion coefficient, Let car n begin braking at time st to reach road segment ei. n,st The velocity at the starting point;

[0085] Step 2.3: Calculate the distance S traveled by the car from time st until time t when braking begins. n,st,t As shown in the following formula:

[0086]

[0087] In the formula, For road section si n,st The road surface adhesion coefficient, For road section ei n,st The starting coordinates, Let car n begin braking at time st to reach road segment ei. n,st At the starting point, under condition t n,st,i <t≤t n,st,i+1 The range of i in the equation is i = si. n,st +1,si n,st +2,...,ei n,st -1;

[0088] Step 2.4: Assume that at time st, the preceding vehicle brakes suddenly with maximum deceleration until it stops; the following vehicle first moves at a constant speed for a duration of reaction time τ, and then brakes with maximum deceleration until it stops. Calculate the distance Srb traveled by the following vehicle from time st to time t. n,st,t As shown in the following formula:

[0089]

[0090] In the formula, S n,st+τ,t Let n be the distance traveled by car n from time st+τ until time t;

[0091] Step 2.5: Calculate the minimum safe distance SDmin based on the braking process, considering the adhesion coefficient, as proposed in this paper. n+1 (t), as shown in the following formula:

[0092] SDmin n+1 (t)=max(Srb n,t,element -S n,t,element ,0)+L n +d,

[0093] In the formula, Srb n+1,t,element Let S be the distance traveled by car n+1 starting from time t, initially moving at a constant speed for one reaction time, then braking until time element. n,t,element Let L be the distance traveled by car n from time t when it starts braking until time element. n Let n be the length of the car, d be the stationary safety distance, and the range of values ​​for element is shown in the following formula:

[0094] element∈{t+τ,et n,t ,et n+1,t+τ}∪{t n,t,i|i=si n,t +1,si n,t +2,...,ei n,t}∪{t n+1,t+τ,i |i=si n+1,t+τ +1,si n+1,t+τ +2,...,ei n+1,t+τ},

[0095] Step 2.6: Calculate the expected safety distance SDexp n+1 (t) and maximum safe distance SDmax n+1 (t), as shown in the following formula:

[0096] SDexp n+1 (t)=SDmin n+1 (t)+x′ n+1 (t)*τ,

[0097] SDmax n+1 (t)=SDexp n+1 (t)+V*τ,

[0098] In the formula, V is the maximum permissible speed on the road, and x′ n+1 (t) represents the speed of car n+1 at time t.

[0099] The braking control method disclosed in this invention, which considers the real-time adhesion coefficient, further includes step 3: adjusting the speed of the following vehicle according to the braking control method based on the safe distance model constructed in step 2.

[0100] Furthermore, in step 3, based on the constructed safe distance model, the speed of the following vehicle is adjusted according to the braking control method. The specific steps are as follows:

[0101] Calculate the acceleration a of the rear vehicle at time t+τ. n+1 (t+τ), as shown in the following equation:

[0102]

[0103] In the formula, a n+1 (t+τ) represents the acceleration of car number n+1 at time t+τ, x n+1 (t+τ) represents the position of car n+1 at time t+τ, μ(x) n+1 (t+τ) represents x n+1 The road adhesion coefficient at coordinate (t+τ), g is the acceleration due to gravity, -μ(x n+1 (t+τ))*g is the expression at x n+1 The maximum deceleration at the (t+τ) coordinate is Δx. n(t) represents the distance between car n and car n+1 at time t, SDmin n+1 (t), SDexp n+1 (t) and SDmax n+1 (t) represents the minimum safe distance, expected safe distance, and maximum safe distance based on the braking process, considering the adhesion coefficient; α is the adjustment coefficient; τ is the reaction time; and C n+1 For the maximum comfort acceleration of the car at n+1, the step function s(u) is shown in the following equation:

[0104]

[0105] The braking control method disclosed in this invention, which considers the real-time adhesion coefficient, can compare the safety distance model based on the braking process that considers the adhesion coefficient with the Berkeley safety distance model to verify the accuracy of the safety distance calculated by the safety distance model based on the braking process that considers the adhesion coefficient.

[0106] The specific steps are as follows:

[0107] Step 4.1: Simulate the scenario where the road surface adhesion coefficient changes from μ0 to μ1 at x1 during vehicle braking, and calculate the Berkeley safety distance.

[0108] The Berkeley safe distance is calculated as follows:

[0109]

[0110] In the formula, x n (t) represents the position of vehicle n at time t, x′ n (t) represents the velocity of vehicle n at time t, μ(x) n (t) indicates that in x n (t) represents the road adhesion coefficient at coordinate (t), g is the acceleration due to gravity, -μ(x) n (t))*g is the expression at x n (t) represents the maximum deceleration at coordinate (t), τ represents the reaction time, and L represents the maximum deceleration at coordinate (t). n Let d be the length of vehicle n, d be the stationary safety distance, and n and n+1 be the vehicle numbers, where n represents the preceding vehicle and n+1 represents the following vehicle.

[0111] The minimum safe distance based on the braking process, considering the coefficient of adhesion, and the difference between the two (Berkeley safe distance minus the minimum safe distance based on the braking process considering the coefficient of adhesion) are shown in the appendix. Figure 2 Appendix Figure 3 and attached Figure 4 As shown.

[0112] In this context, μ0 is set to 0.2, μ1 ranges from 0.1 to 0.9, the positions of the front and rear vehicles are 185m and 0m respectively, and the speeds of the front and rear vehicles are 10m / s and 20m / s respectively.

[0113] Taking μ1 as 0.1 and x1 as 20.1m as an example, the braking process of the following vehicle in the Berkeley safety distance model and the proposed safety distance model is shown in the appendix. Figure 5 As shown. (Through the attached...) Figure 5 It is evident that the proposed safety distance model considers the influence of the road surface adhesion coefficient on the braking distance during vehicle braking. When the road surface adhesion coefficient changes from 0.2 to 0.1, the vehicle's maximum deceleration changes. In contrast, the Berkeley safety distance model ignores this change in the road surface adhesion coefficient during braking. Compared to the Berkeley safety distance model, the proposed safety distance model based on the braking process, which considers the adhesion coefficient, takes into account the influence of the road surface adhesion coefficient on the braking distance during vehicle braking, resulting in a more accurate calculated braking distance. Furthermore, through the... Figure 4 It can be seen that the greater the change in the road surface adhesion coefficient during braking, and the earlier the change occurs, the greater the impact of the change in the road surface adhesion coefficient on the braking distance.

[0114] Step 4.2: Analyze the impact of changes in road surface adhesion coefficient on the minimum safe distance and Berkeley safe distance based on the braking process, taking into account the adhesion coefficient.

[0115] Step 4.3: Compare the minimum safe distance based on the braking process, which takes into account the coefficient of adhesion, with the Berkeley safe distance, and analyze the differences between the two.

[0116] The braking control method disclosed in this invention, which considers the real-time adhesion coefficient, can simulate a convoy following scenario to verify the safety and stability of a safe distance model based on the braking process that considers the adhesion coefficient.

[0117] The specific steps are as follows:

[0118] Step 5.1: At the initial moment, all cars in the convoy are stationary and maintain a certain distance between adjacent cars. The lead car first accelerates uniformly, then moves at a constant speed, and finally decelerates uniformly until it stops. The following cars in the convoy move according to the braking control method. The following process of the convoy in the three stages of starting, moving at a constant speed and stopping is simulated.

[0119] The convoy following scenario is set as follows: Initially, a convoy of five cars is stationary on a road with a coefficient of friction of 0.5, and adjacent cars maintain a distance of 10 meters. The lead car initially moves at 2 m / s. 2The vehicle accelerates uniformly for 10 seconds, then moves at a constant speed for 60 seconds, and finally decelerates uniformly with maximum deceleration until it stops. Subsequent vehicles in the convoy follow the vehicle according to the braking control method. The convoy's starting, constant speed, and stopping phases were simulated, and the specific results are attached. Figure 6 and attached Figure 7 As shown;

[0120] Step 5.2: Analyze the stability of the convoy following process;

[0121] In the following scenario set in step 5.1, the lead vehicle starts to travel at a constant speed at the 10th second, and the subsequent vehicles travel according to the braking control method. At the 42.11th second, all vehicles in the convoy maintain the same speed and spacing and travel at a constant speed, and the convoy enters a stable state.

[0122] Step 5.3: Analyze the safety of the convoy following process.

[0123] Following the car-following scenario set in step 5.1, the ratio of the actual distance to the calculated minimum safe distance during the car-following process is obtained. The specific results are attached. Figure 8 As shown, the safety of the convoy following process is analyzed. The distance between vehicles is always no less than the calculated minimum safe distance during the following process, which can ensure the safety of the convoy following process.

[0124] In the braking control method of the present invention that considers the real-time adhesion coefficient, the parameters of the above steps are set, and the value and calculation process of each step are as follows.

[0125] The road and vehicle information obtained in Step 1 is as follows: The road consists of two road segments with different adhesion coefficients. At time t, the positions of the preceding and following vehicles are 185m and 0m, respectively, and their speeds are 10m / s and 20m / s, respectively. The parameter settings are as follows:

[0126] μ0 = 0.2

[0127] μ1 = 0.1

[0128] x0=0m

[0129] x1 = 20.1m

[0130] x2=10000m

[0131] x n (t)=185m

[0132] x n+1 (t)=0m

[0133] x′ n (t)=10m / s

[0134] x′n+1 (t)=20m / s

[0135] In step 2, at time t, the vehicle in front brakes urgently with maximum deceleration until it stops; the vehicle behind first moves at a constant speed for a duration of reaction time τ, and then brakes with maximum deceleration until it stops. The parameter settings and calculation results are as follows:

[0136] τ = 1s

[0137] L n =4m

[0138] d = 5m

[0139] g = 10 m / s 2

[0140] V = 25 m / s

[0141] t=0s

[0142] si n+1,t+τ =0

[0143] ei n+1,t+τ =1

[0144] x n+1 (t+τ)=x n+1 (t)+x′ n+1 (t)*τ=20m

[0145]

[0146]

[0147]

[0148]

[0149]

[0150]

[0151]

[0152] SDexp n+1 (t)=SDmin n+1 (t)+x′ n+1 (t)*τ=208.9m

[0153] SDmax n+1 (t)=SDexp n+1 (t)+V*τ=233.9m

[0154] The parameter settings and calculation results in step 3 are as follows:

[0155] α = 2.5

[0156] C n+1 =3m / s 2

[0157] Δx n (t)=x n (t)-x n+1 (t)=185m

[0158]

[0159] In step 4, the value of μ1 is set to range from 0.1 to 0.9. The Berkeley safety distance is calculated, taking into account the minimum safety distance based on the braking process and the adhesion coefficient, and the difference between the two (Berkeley safety distance minus the minimum safety distance based on the braking process considering the adhesion coefficient). The specific results are shown in the attached figure. Figure 3 and attached Figure 4 As shown in the figure. Taking μ1 as 0.1 and x1 as 20.1m as an example, the braking process of the following vehicle in the Berkeley safety distance model and the proposed safety distance model is shown in the appendix. Figure 5 As shown. When μ1 is set to 0.1, the minimum safe distance based on the braking process, considering the adhesion coefficient (calculated in step 2), is 178.9 m. The Berkeley safe distance calculation results are as follows:

[0160]

[0161] In step 5, the convoy following scenario is set as follows: Initially, the convoy of five vehicles is stationary on a road with a coefficient of friction of 0.5, and adjacent vehicles maintain a distance of 10m. The road surface adhesion coefficient is 0.5. The lead vehicle initially travels at 2m / s. 2 The vehicle accelerates uniformly for 10 seconds, then moves at a constant speed for 60 seconds, and finally decelerates uniformly with maximum deceleration until it stops. Subsequent vehicles in the convoy follow the vehicle according to the braking control method. The convoy's starting, constant speed, and stopping phases were simulated, and the specific results are attached. Figure 6 and attached Figure 7 As shown in the attached figure, the ratio of the actual distance to the calculated minimum safe distance during the car-following process is as follows. Figure 8 As shown. Taking the 5th second as an example, the calculated parameters are as follows:

[0162] t = 5s

[0163] x1(t) = 65m

[0164] x2(t)=39.514m

[0165] x3(t)=22.980m

[0166] x4(t) = 11.205m

[0167] x5(t)=0.884m

[0168] x1′(t)=10m / s

[0169] x2′(t)=5.867m / s

[0170] x3′(t)=2.299m / s

[0171] x4′(t)=0.794m / s

[0172] x5′(t)=0.421m / s

[0173] SDmin2(t)=9m

[0174] SDmin3(t)=9m

[0175] SDmin4(t)=9.328m

[0176] SDmin5(t)=9.376m

[0177] SDexp2(t)=14.867m

[0178] SDexp3(t)=11.299m

[0179] SDexp4(t)=10.122m

[0180] SDexp5(t)=9.797m

[0181] a2(t)=2.213m / s 2

[0182] a3(t) = 1.321 m / s 2

[0183] a4(t) = 0.474 m / s 2

[0184] a5(t) = 0.134 m / s 2 .

[0185] The present invention also includes a braking process-based control device that takes into account the coefficient of adhesion, comprising:

[0186] The information acquisition unit acquires information on the changes in road surface adhesion coefficient, the coordinates of each vehicle at each moment, and the speed information of each vehicle at each moment in real time through inter-vehicle communication and sensor equipment.

[0187] Based on vehicle and road information, a safe distance model based on the braking process is constructed, taking into account the adhesion coefficient.

[0188] The adjustment unit adjusts the speed of the following vehicle according to the braking control method, based on the constructed safe distance model.

[0189] The accuracy verification unit compares the safety distance model based on the braking process, which considers the adhesion coefficient, with the Berkeley safety distance model to verify the accuracy of the safety distance calculated by the safety distance model based on the braking process, which considers the adhesion coefficient.

[0190] To verify the safety unit, a simulated convoy following scenario was used to verify the safety and stability of the safety distance model based on the braking process, which takes into account the adhesion coefficient.

[0191] The present invention also provides a braking process-based control system that takes into account the coefficient of adhesion, the system including a processor and a memory, the processor executing computer instructions stored in the memory to implement the above method.

[0192] The present invention also provides a computer-readable storage medium for storing non-transitory computer-readable instructions that, when executed by a computer, cause the computer to perform the above-described method.

[0193] It should be noted that the computer-readable medium described in this disclosure can be a computer-readable signal medium or a computer-readable storage medium, or any combination thereof. A computer-readable storage medium can be, for example,—but not limited to—an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination thereof. More specific examples of a computer-readable storage medium may include, but are not limited to: an electrical connection having one or more wires, a portable computer disk, a hard disk, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage device, magnetic storage device, or any suitable combination thereof. In this disclosure, a computer-readable storage medium can be any tangible medium containing or storing a program that can be used by or in connection with an instruction execution system, apparatus, or device. In this disclosure, a computer-readable signal medium can include a data signal propagated in baseband or as part of a carrier wave, carrying computer-readable program code. Such propagated data signals can take various forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination thereof. A computer-readable signal medium can be any computer-readable medium other than a computer-readable storage medium, which can send, propagate, or transmit a program for use by or in connection with an instruction execution system, apparatus, or device. The program code contained on the computer-readable medium can be transmitted using any suitable medium, including but not limited to: wires, optical fibers, RF (radio frequency), etc., or any suitable combination thereof.

[0194] The aforementioned computer-readable medium may be included in the aforementioned electronic device; or it may exist independently and not assembled into the electronic device.

[0195] Computer program code for performing the operations of this disclosure can be written in one or more programming languages ​​or a combination thereof, including object-oriented programming languages ​​such as Java, Smalltalk, and C++, and conventional procedural programming languages ​​such as the "C" language or similar programming languages. The program code can be executed entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In cases involving remote computers, the remote computer can be connected to the user's computer via any type of network—including a local area network (LAN) or a wide area network (WAN)—or can be connected to an external computer (e.g., via the Internet using an Internet service provider).

[0196] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of this disclosure. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code containing one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions indicated in the blocks may occur in a different order than those indicated in the drawings. For example, two consecutively indicated blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, can be implemented using a dedicated hardware-based system that performs the specified function or operation, or using a combination of dedicated hardware and computer instructions.

[0197] The units described in the embodiments of this disclosure can be implemented in software or hardware. The names of the units are not, in some cases, intended to limit the specific unit.

[0198] The above description is merely a preferred embodiment of this disclosure and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of this disclosure is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the above-described concept. For example, technical solutions formed by substituting the above features with (but not limited to) technical features disclosed in this disclosure that have similar functions.

Claims

1. A brake control method considering real-time adhesion coefficient, characterized by, The method comprises the following steps: Step 1: obtaining the road surface adhesion coefficient information of each section, the coordinate information of each vehicle at each time, and the speed information of each vehicle at each time; Step 2: based on the obtained variation information of the road surface adhesion coefficient of each section, the coordinates of each vehicle at each time, and the speed information of each vehicle at each time, a safety distance model considering adhesion coefficient braking control is constructed; Step 3: based on the constructed safety distance model, the speed of the rear vehicle is adjusted according to the braking control method; the safety distance model considering adhesion coefficient based on the braking process in step 2 specifically comprises: Step 2.1: assuming that at time st, vehicle n brakes at the maximum deceleration until it stops, and the road sections where the vehicle is located at the beginning and end of the braking process are different; The number of the road section where the car n is located at the start time of the braking process is determined as , and the number of the road section where the car n is located at the end time of the braking process is determined as ; It is only necessary to compare the coordinates of the start and end points of each section to determine , said denotes the number of the section in which the car n is at the start of the braking process at the time st, as follows: wherein is the start coordinate of the road segment is the end coordinate of the road segment is the start coordinate of the road segment is the end coordinate of the road segment denotes the number of the road segment on which the car n starts braking at time st until the end of braking, is calculated as follows: ， ， wherein is the speed of the car n at the start of the braking on the road section i at the time st, is the speed of the car n at the start of the braking on the road section i at the time st, is the acceleration of gravity, is the road adhesion coefficient of the road section i, is the start coordinate of the road section i, is the end coordinate of the road section i, is the coordinate of the car n at the time st, is the speed of the car n at the time st. Step 2.2: Calculate the time at which the car n starts braking at st and ends braking at and the time at which the braking ends as follows: t = st + Tbrake ， ， wherein is the speed of the car n at time st, is the road adhesion coefficient of the road section , is the speed of the car n at time st when it starts braking to reach the beginning of the road section . Step 2.3: Calculate the distance traveled by car n from the time st until the time t while braking As shown in the following equation: ， wherein is the road surface adhesion coefficient of the road section , is the start point coordinate of the road section , is the time at which the car n reaches the start point of the road section at time st, under the condition that i ranges from ; Step 2.4: Assume that at st moment, the front vehicle brakes with maximum deceleration until stopping; the rear vehicle first moves with uniform velocity, the duration being the reaction time , and then brakes with maximum deceleration until stopping; the distance traveled by the rear vehicle from st moment to t moment is calculated , as shown in the following formula: ， In the formula, is the distance driven by the car n from the moment the braking started until the moment t Step 2.5: Calculate the minimum safety distance based on the braking process considering the adhesion coefficient proposed in this document As shown in the following equation: ， wherein is the distance traveled by the car n+1 from time t at a constant speed for a reaction time and then braking until time t+Tn+1, is the distance traveled by the car n from time t until braking until time t+Tn, is the length of the car n, d is the standstill safety distance, has the following value range: ； Step 2.6: Calculate the expected safety distance and the maximum safety distance as shown in the following equation: ， ， wherein is the maximum speed allowed for the road, is the speed of the car n+1 at time t.

2. The brake control method considering real-time adhesion coefficient according to claim 1, characterized in that, The control algorithm in step 3 is specifically: ， In the formula, for The acceleration of the car with vehicle number n+1 at time n. Indicates that car n+1 is in Location at any given moment Indicates in The road surface adhesion coefficient at the coordinates, It is the acceleration due to gravity. That is to be in The maximum deceleration at the coordinate is Let be the distance between car n and car n+1 at time t. , and To determine the minimum safe distance, expected safe distance, and maximum safe distance based on the braking process, taking into account the coefficient of adhesion. To adjust the coefficient, For reaction time, For the maximum comfort acceleration of the car (n+1), the step function is... As shown in the following formula: 。 3. A control system based on the braking process considering adhesion coefficient, the system comprising a processor and a memory, the processor executing computer instructions stored in the memory to implement the method of claim 1 or 2.

4. A computer readable storage medium for storing non-transitory computer readable instructions, when the non-transitory computer readable instructions are executed by a computer, the computer executes the method of claim 1 or 2.

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