A safety control method for ACC vehicle following considering communication delay

Abstract

The present invention discloses an ACC vehicle following safety control method considering communication delay. Based on an established ACC vehicle speed decision model that considers the confidence level of vehicle speed and position, a vehicle speed and position difference feedback control strategy considering communication delay is proposed. The evolution of the ACC vehicle rear-end collision probability measure with and without the control strategy is analyzed. This method can be widely used in fields such as autonomous driving and fleet control.

Description

Technical Field

[0001] The present invention relates to the field of automatic driving control methods, and in particular to an ACC vehicle following safety control method taking communication delay into consideration. Background Art

[0002] During autonomous driving, onboard sensors perceive vehicle information, including speed and position. However, due to the limited confidence level of this sensor information, this can impact the safety of ACC (Accelerated Collision Avoidance) vehicle platooning. To ensure safety during ACC, numerous researchers have conducted in-depth research on longitudinal active safety control technologies for ACC vehicles and developed various ACC systems. With the rapid development of intelligent and connected vehicles, hazard identification and collision avoidance control during ACC, based on vehicle-to-vehicle information interaction, has become a hot topic in current research on collaborative safety technologies.

[0003] In ACC platooning, fixed inter-vehicle spacing and traditional headway timing are the two primary control strategies. However, these strategies are ineffective when the vehicle speed and position information sensed by onboard sensors has a certain confidence level. Therefore, a safe ACC platooning control method that accounts for communication delay is needed, which has important engineering applications for the development of autonomous vehicles. Summary of the Invention

[0004] The present invention provides an ACC vehicle following safety control method taking communication delay into consideration, so as to solve the problem of poor control effect in the prior art ACC vehicle following safety control method.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] Consider an ACC vehicle following safety control method considering communication delay, which includes the following steps:

[0007] Step 1: Construct the motion equations of a platoon following n unmanned vehicles as shown in formulas (1) and (2):

[0008]

[0009]

[0010] Among them, a n (t+τ) represents the acceleration of the nth vehicle at time t+τ; τ represents the ACC vehicle braking reaction time; α represents the acceleration sensitivity coefficient; represents the safety margin of the nth vehicle at time t; SM D represents the expected safety margin;

[0011] τ2 represents the vehicle emergency braking reaction time; v n (t) and v n-1 (t) represents the speed of vehicle n and n-1 respectively; d represents the maximum braking deceleration of the vehicle; Δx n (t) represents the vehicle gap, and Δx n (t) = x n-1 (t)-x n (t)-l n-1 , x n (t) and x n-1 (t) are the location information of the nth and n-1th vehicles, l n-1 is the length of the n-1th car;

[0012] Φ -1 (·) represents the inverse of the standard normal distribution; β represents the confidence level of the vehicle speed; γ represents the confidence level of the position; ζ(v n-1 )and They represent the standard deviation of the perceived vehicle speed error and the standard deviation of the vehicle gap error, ζ(v n-1 )and The values ​​of are related to the vehicle speed and the vehicle gap respectively;

[0013] Step 2: Construct the vehicle speed and position difference feedback control term C considering communication delay n (t) is shown in formula (3):

[0014] C n (t) = κ1(Δx n (t-τ * )-Δx n (t))+κ2(v n (t-τ * )-v n (t)) (3),

[0015] Among them, τ * represents the communication delay response time, κ1 and κ2 both represent the feedback gain coefficients of the control items;

[0016] Step 3: Add the feedback control term obtained in step 2 to the following motion equation of step 1 to obtain the following motion equation of the unmanned vehicle platoon that takes into account the speed and position difference feedback of the communication delay, as shown in formula (4):

[0017]

[0018] The platoon control of unmanned vehicles is realized based on the following motion equation shown in formula (4).

[0019] A further step 3 also includes:

[0020] Construct an exponential decay function to estimate the probability of a rear-end collision between the front vehicle n-1 and the rear vehicle n at time t As shown in formula (5):

[0021]

[0022] In formula (5), Represents the safety margin of a given vehicle rear-end collision risk indicator Under the following conditions, the probability of a rear-end collision between the front vehicle n-1 and the rear vehicle n at time t is: c is a constant variable.

[0023] Furthermore, the speed and position of all vehicles are updated according to the following rules:

[0024] The update formula of velocity is v n (t) = v n (t-Δt)+a(t-Δt)×Δt,n=1,2,…N;

[0025] The update formula for position is

[0026] Where Δt is the acceleration adjustment time.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] This invention aims to ensure stable driving in platoons of autonomous vehicles. The technical solution uses the expected safety margin following model as the ACC speed decision model. It constructs a speed and position difference feedback control term that accounts for communication delays. The impact of the control term on platoon following safety is compared and analyzed with and without the control term. This method has broad application in fields such as autonomous driving and fleet control. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a flow chart of a method according to an embodiment of the present invention.

[0030] Figure 2 This is the evolution diagram of the rear-end collision probability measure of an unmanned vehicle fleet, where: (a) is the evolution diagram without control strategy, and (b) is the evolution diagram with control strategy. DETAILED DESCRIPTION

[0031] To help those skilled in the art better understand the present invention, the following detailed description of the embodiments of the present invention is provided in conjunction with the accompanying drawings and examples. This will help those skilled in the art to fully understand and implement the present invention by applying technical means to solve technical problems and achieve corresponding technical effects. The embodiments of the present invention and the various features therein may be combined with each other as long as they do not conflict with each other, and the resulting technical solutions are all within the scope of protection of the present invention.

[0032] Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0033] It should be noted that the terms "include" and "have" in the specification, claims and drawings of the present invention and any variations thereof are intended to cover non-exclusive inclusions.

[0034] like Figure 1 As shown, this embodiment discloses an ACC vehicle following safety control method considering communication delay, including the following steps:

[0035] Step 1: Using the expected safety margin model as the ACC speed decision model, considering the perception level of the onboard sensors of the unmanned vehicles, introducing the confidence levels β and γ of the vehicle speed and position, the motion equations of the platoon following consisting of n unmanned vehicles are constructed as shown in formulas (1) and (2):

[0036]

[0037]

[0038] Among them, a n (t+τ) represents the acceleration of the nth vehicle at time t+τ; τ represents the ACC vehicle braking reaction time; α represents the acceleration sensitivity coefficient; represents the safety margin of the nth vehicle at time t; SM D represents the expected safety margin;

[0039] τ2 represents the vehicle emergency braking reaction time; v n (t) and v n-1 (t) represents the speed of vehicle n and n-1 respectively; d represents the maximum braking deceleration of the vehicle; Δx n (t) represents the vehicle gap, and Δx n (t) = x n-1 (t)-x n (t)-l n-1 , x n (t) and xn-1 (t) are the location information of the nth and n-1th vehicles, l n-1 is the length of the n-1th car;

[0040] Φ -1 (·) represents the inverse of the standard normal distribution; β represents the confidence level of the vehicle speed; γ represents the confidence level of the position; ζ(v n-1 )and They represent the standard deviation of the perceived vehicle speed error and the standard deviation of the vehicle gap error, ζ(v n-1 )and The values ​​of are related to the vehicle speed and the vehicle gap respectively;

[0041] Step 2: Simulate the motion state of the vehicle platoon when t>0. Assume that the leading vehicle moves according to a pre-specified plan and the unmanned vehicle follows according to the following motion equation. Construct the speed and position difference feedback control term C of the unmanned vehicle platoon considering communication delay. n (t) is shown in formula (3):

[0042] C n (t) = κ1(Δx n (t-τ * )-Δx n (t))+κ2(v n (t-τ * )-v n (t)) (3),

[0043] Among them, τ * represents the communication delay response time, and κ1 and κ2 represent the feedback gain coefficients of the control items.

[0044] Step 3: Add the feedback control term obtained in step 2 to the following motion equation of step 1 to obtain the following motion equation of the unmanned vehicle platoon that takes into account the speed and position difference feedback of the communication delay, as shown in formula (4):

[0045]

[0046] The platoon control of unmanned vehicles is realized based on the following motion equation shown in formula (4).

[0047] At the same time, an exponential decay function is constructed to estimate the probability of a rear-end collision between the front vehicle n-1 and the rear vehicle n at time t. As shown in formula (5):

[0048]

[0049] In formula (5), Represents the safety margin of a given vehicle rear-end collision risk indicator Under the following conditions, the probability of a rear-end collision between the front vehicle n-1 and the rear vehicle n at time t is: c is a constant variable.

[0050] In this embodiment, the speed and position of all vehicles in the unmanned vehicle queue are updated according to the following rules:

[0051] The update formula of velocity is v n (t) = v n (t-Δt)+a(t-Δt)×Δt,n=1,2,…N;

[0052] The update formula for position is

[0053] Where Δt is the acceleration adjustment time.

[0054] In this embodiment, the initial conditions of the vehicle are set as follows:

[0055]

[0056] Among them, x n-1 (0) and v n-1 (0) represents the initial position and initial speed of the n-1th vehicle respectively; represents the initial acceleration of the n-1th vehicle; Indicates that the lead vehicle is The acceleration disturbance after time is 5×10 -2 ×U(-1,1) uniform distribution; represents the initial acceleration of the lead vehicle; represents the acceleration of the lead vehicle at time t; x1(0) represents the initial position of the lead vehicle; L represents the distance between ACC vehicles in the queue.

[0057] This embodiment performs simulation experiments according to the following parameter assignments:

[0058] Vehicle length l = 5m, τ2 = 0.15s, v * =20m / s,α=10m / s 2 ,,τ=0.5s, d = 7.5, ζ = -0.3, SM D =0.9, κ1=-1, κ2=1.5, c=0.2, τ * =0.5s, α=0.9, β=0.5.

[0059] Through simulation experiments, we get Figure 2 The evolution diagram of the ACC vehicle rear-end collision probability measure with and without control strategy is shown in Figure 2. Figure 2It can be seen that the probability of rear-end collision of vehicles in the queue without a control strategy is significantly higher than the probability of rear-end collision of vehicles under the control method of this embodiment taking communication delay into consideration.

[0060] The preferred embodiments of the present invention are described in detail above with reference to the accompanying drawings. The embodiments described in the present invention are merely descriptions of the preferred embodiments of the present invention and do not limit the concept and scope of the present invention. The various specific technical features described in the above specific embodiments can be combined in any suitable manner unless there is any contradiction. Such combinations should also be regarded as the contents disclosed in this disclosure as long as they do not violate the concept of the present invention. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0061] The present invention is not limited to the specific details of the above-mentioned embodiments. Within the scope of the technical concept of the present invention and without departing from the design concept of the present invention, various modifications and improvements made to the technical solution of the present invention by those skilled in the art should fall within the scope of protection of the present invention. The technical contents for which protection is sought in the present invention have been fully recorded in the claims.

Claims

1. A method for ACC vehicle following safety control considering communication delay, characterized in that: The following steps are involved: Step 1: Construct the motion equations of a platoon following n unmanned vehicles as shown in formulas (1) and (2): Among them, a n (t+τ) represents the acceleration of the nth vehicle at time t+τ; τ represents the ACC vehicle braking reaction time; α represents the acceleration sensitivity coefficient; represents the safety margin of the nth vehicle at time t; SM D represents the expected safety margin; τ2 represents the vehicle emergency braking reaction time; v n (t) and v n-1 (t) represents the speed of vehicle n and n-1 respectively; d represents the maximum braking deceleration of the vehicle; Δx n (t) represents the vehicle gap, and Δx n (t) = x n-1 (t)-x n (t)-l n-1 , x n (t) and x n-1 (t) are the location information of the nth and n-1th vehicles, l n-1 is the length of the n-1th car; Φ -1 (·) represents the inverse of the standard normal distribution; β represents the confidence level of the vehicle speed; γ represents the confidence level of the position; ζ(v n-1 )and They represent the standard deviation of the perceived vehicle speed error and the standard deviation of the vehicle gap error, ζ(v n-1 )and The values ​​of are related to the vehicle speed and the vehicle gap respectively; Step 2: Construct the vehicle speed and position difference feedback control term C considering communication delay n (t) is shown in formula (3): C n (t)=κ1(Δx n (t-τ * )-Δx n (t))+κ2(v n (t-τ * )-v n (t)) (3), Among them, τ * represents the communication delay response time, κ1 and κ2 both represent the feedback gain coefficients of the control items; Step 3: Add the feedback control term obtained in step 2 to the following motion equation of step 1 to obtain the following motion equation of the unmanned vehicle platoon that takes into account the speed and position difference feedback of the communication delay, as shown in formula (4): The platoon control of unmanned vehicles is realized based on the following motion equation shown in formula (4).

2. The ACC vehicle following safety control method considering communication delay according to claim 1, characterized in that: Step 3 also includes: Construct an exponential decay function to estimate the probability of a rear-end collision between the front vehicle n-1 and the rear vehicle n at time t As shown in formula (5): In formula (5), Represents the safety margin of a given vehicle rear-end collision risk indicator Under the following conditions, the probability of a rear-end collision between the front vehicle n-1 and the rear vehicle n at time t is: c is a constant variable.

3. The ACC vehicle following safety control method considering communication delay according to claim 1 or 2, characterized in that: The speed and position of all vehicles are updated according to the following rules: The update formula of velocity is v n (t) = v n (t-Δt)+a(t-Δt)×Δt,n=1,2,…N; The update formula for position is Where Δt is the acceleration adjustment time.

Images