Speed control method, device, apparatus and computer readable storage medium

Abstract

The application provides a speed control method, device, equipment and computer readable storage medium, the method comprises: under the condition of meeting the safety distance between the ego vehicle and the preceding vehicle, obtaining a following vehicle model, the following vehicle model comprises a motion equation describing a plurality of longitudinal trajectories, the motion equation describes the relationship between the displacement of the ego vehicle on the longitudinal trajectory and the time; solving the following vehicle model to obtain a solution; and controlling the speed of the ego vehicle based on the solution; wherein the plurality of longitudinal trajectories comprise a first longitudinal trajectory, a second longitudinal trajectory, a third longitudinal trajectory and a fourth longitudinal trajectory; the acceleration change rate of the first longitudinal trajectory is equal to the acceleration change rate of the third longitudinal trajectory, and the acceleration of the second longitudinal trajectory and the acceleration of the fourth longitudinal trajectory are constant values. The application can ensure the controllability and stability of following driving.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of speed control, and in particular, to a speed control method, device, equipment and computer readable storage medium. BACKGROUND

[0002] The progress of artificial intelligence technology has promoted the rapid landing of automatic driving and assisted driving. Intelligent driving technology not only needs to ensure the safety of the vehicle during driving, but also needs to take into account the comfort, and the comfort is often closely related to the control of speed. The car-following function is an extremely important function in automatic driving or assisted driving, and the quality of car-following is also an important indicator to evaluate the performance of automatic driving or assisted driving. After the system obtains the control target and environmental perception information, the speed control of car-following needs to complete the transition from comfort to safety. Some speed controls use quintic polynomials or quartic polynomials, but these control methods only constrain the initial and final states of car-following, and the intermediate states are relatively uncontrollable. SUMMARY

[0003] The present application provides a speed control method, device, equipment and computer readable storage medium to solve the technical problem of how to improve the controllability of vehicle car-following.

[0004] To solve the above technical problems, the first aspect of the present application provides a speed control method, comprising:

[0005] Under the condition of meeting the safety distance between the ego vehicle and the front vehicle, a car-following model is obtained, the car-following model comprising a motion equation describing a multi-segment longitudinal trajectory, the motion equation describing the relationship between the displacement of the ego vehicle on the longitudinal trajectory and time;

[0006] The car-following model is solved to obtain a solution result, and the speed of the ego vehicle is controlled based on the solution result;

[0007] The multi-segment longitudinal trajectory comprises a first segment longitudinal trajectory, a second segment longitudinal trajectory, a third segment longitudinal trajectory and a fourth segment longitudinal trajectory; the acceleration change rate of the first segment longitudinal trajectory is equal to the acceleration change rate of the third segment longitudinal trajectory, and the acceleration of the second segment longitudinal trajectory and the acceleration of the fourth segment longitudinal trajectory are constant values.

[0008] The follow-up model of the application comprises a motion equation of a multi-segment longitudinal trajectory, the motion equation describing the relationship between the displacement of the ego vehicle and the time on the longitudinal trajectory, by designing the above multi-segment longitudinal trajectory in the follow-up model, i.e. there are multiple control segment points in the follow-up process, compared with the control scheme of the prior art adopting a quintic polynomial or a quartic polynomial, not only the initial and final states are constrained, but also the ego vehicle states of each control segment point are constrained, ensuring the controllability of the initial state, the final state and the intermediate state in the follow-up driving process of the ego vehicle; in addition, the multi-segment longitudinal trajectory comprises a first segment longitudinal trajectory, a second segment longitudinal trajectory, a third segment longitudinal trajectory and a fourth segment longitudinal trajectory, the acceleration change rate of the first segment longitudinal trajectory is equal to the acceleration change rate of the third segment longitudinal trajectory, and the acceleration of the second segment longitudinal trajectory and the acceleration of the fourth segment longitudinal trajectory are constant values, so that the transformation of the speed of the ego vehicle in the whole follow-up driving process is relatively smooth, the experience of the user is optimized, and the stability of the follow-up driving is ensured.

[0009] As a preferred scheme of the first aspect, the motion equation of the first segment longitudinal trajectory is:

[0010] f1(t)=a0×t 3 +b0×t 2 +c0t+d0;

[0011] The motion equation of the second segment longitudinal trajectory is:

[0012] f2(t)=a1×t 2 +b1×t+c1;

[0013] The motion equation of the third segment longitudinal trajectory is:

[0014] f3(t)=a2×t 3 +b2×t 2 +c2×t+d2;

[0015] The motion equation of the fourth segment longitudinal trajectory is:

[0016] f4(t)=a3t+b3;

[0017] Wherein, f1(t) is the displacement of the ego vehicle at the t time in the first segment longitudinal trajectory, f2(t) is the displacement of the ego vehicle at the t time in the second segment longitudinal trajectory, f3(t) is the displacement of the ego vehicle at the t time in the third segment longitudinal trajectory, and f4(t) is the displacement of the ego vehicle at the t time in the fourth segment longitudinal trajectory, a0, b0, c0, d0, a1, b1, c1, a2, b2, c2, d2, a3 and b3 are all to-be-solved parameters.

[0018] As a preferred scheme of the first aspect, the follow-up model is solved to obtain a solving result, comprising:

[0019] solving the car-following model under the preset constraint condition to obtain a solution result;

[0020] The preset constraint condition comprises: longitudinal displacement continuity of a connection position of the first longitudinal trajectory and the second longitudinal trajectory, longitudinal velocity continuity of the connection position of the first longitudinal trajectory and the second longitudinal trajectory, longitudinal acceleration equality of the connection position of the first longitudinal trajectory and the second longitudinal trajectory, longitudinal displacement continuity of a connection position of the second longitudinal trajectory and the third longitudinal trajectory, longitudinal velocity continuity of the connection position of the second longitudinal trajectory and the third longitudinal trajectory, longitudinal acceleration equality of the connection position of the second longitudinal trajectory and the third longitudinal trajectory, longitudinal velocity of the third longitudinal trajectory at the end being the target speed, longitudinal acceleration of the third longitudinal trajectory at the end being zero, longitudinal displacement continuity of a connection position of the third longitudinal trajectory and the fourth longitudinal trajectory, longitudinal velocity continuity of the connection position of the third longitudinal trajectory and the fourth longitudinal trajectory, longitudinal acceleration change rate of the first longitudinal trajectory and the second longitudinal trajectory being a constant value, and total planning trajectory time length of the first longitudinal trajectory, the second longitudinal trajectory, the third longitudinal trajectory and the fourth longitudinal trajectory being a preset value.

[0021] As a preferred scheme of the first aspect, the solving of the car-following model to obtain a solution result comprises:

[0022] sampling the solution result of the car-following model in a preset sampling interval to obtain the plurality of analytical solutions, and determining the plurality of analytical solutions as the solution result; wherein the sampling interval is [0, T].

[0023] As a preferred scheme of the first aspect, the solving of the car-following model to obtain a solution result comprises:

[0024] sampling the solution result of the car-following model in a preset sampling interval to obtain the plurality of analytical solutions, and determining the plurality of analytical solutions as the solution result; wherein the sampling interval is [0, T], and T represents total planning trajectory time length of the first longitudinal trajectory, the second longitudinal trajectory, the third longitudinal trajectory and the fourth longitudinal trajectory.

[0025] As a preferred scheme of the first aspect, the control of the speed of the ego vehicle based on the solution result comprises:

[0026] calculating the cost of each analytical solution through a preset cost function, and selecting an analytical solution with the minimum cost, and controlling the speed of the ego vehicle based on the analytical solution with the minimum cost;

[0027] The preset cost function comprises:

[0028] f cost= w1 x cost speed + w2 x cost comfort + w3 x cost collision + w4 x cost centerAcc +

[0029] w5 x cost follow ;

[0030] cost speed = |f4(T)' - V s2 |;

[0031] cost comfort = |f2(t a )”|;

[0032]

[0033] cost2 = V t x V t x k;

[0034]

[0035] cost3 = max(0, X t - X safet );

[0036] wherein f cost is the cost function, cost speed is the speed cost, cost comfort is the comfort cost, cost collision is the collision cost, cost centerAcc is the centripetal acceleration cost, cost follow is the stable following cost, w1, w2, w3, w4 and w5 are weights corresponding to the cost function, the speed cost, the comfort cost, the collision cost, the centripetal acceleration cost and the stable following cost respectively, k represents a lane curvature at a position of the ego vehicle, V t represents a longitudinal speed of the ego vehicle at time t, X t represents a longitudinal displacement of the ego vehicle at time t, X tfront represents a longitudinal displacement of a preceding vehicle at time t, f4(T)' represents a longitudinal speed of the ego vehicle at an end of a fourth longitudinal trajectory, f2(t a )” represents a longitudinal acceleration of the ego vehicle at an initial time of a second longitudinal trajectory, V s is a second preset speed value, X safet represents a safety distance at time t, cost1, cost2 and cost3 are intermediate variables.

[0037] As a preferred scheme of the first aspect, the speed control method further comprises:

[0038] when the distance between the ego vehicle and the front vehicle is less than or equal to a preset distance, the target speed is a current speed of the front vehicle;

[0039] when the distance between the ego vehicle and the front vehicle is greater than the preset distance, the target speed is a first preset speed value.

[0040] As a preferred solution of the first aspect, the speed control method further comprises:

[0041] when the current speed of the ego vehicle is greater than a preset speed limit value, or the current acceleration of the ego vehicle is greater than a preset acceleration limit value; the target speed is obtained by golden section, to obtain an updated target speed.

[0042] A second aspect of the present application provides a speed control device, the speed control device comprises an acquisition module and a control module; wherein,

[0043] the acquisition module is configured to acquire a car-following model under the condition that the safety distance between the ego vehicle and the front vehicle is met, the car-following model comprising a motion equation describing a plurality of longitudinal trajectories, the motion equation describing the relationship between the displacement of the ego vehicle on the longitudinal trajectory and the time;

[0044] the control module is configured to solve the car-following model to obtain a solution result; and control the speed of the ego vehicle based on the solution result;

[0045] wherein, the plurality of longitudinal trajectories comprises a first longitudinal trajectory, a second longitudinal trajectory, a third longitudinal trajectory and a fourth longitudinal trajectory; the acceleration change rate of the first longitudinal trajectory is equal to the acceleration change rate of the third longitudinal trajectory, and the acceleration of the second longitudinal trajectory and the acceleration of the fourth longitudinal trajectory are constant values.

[0046] In some preferred embodiments of the second aspect, the motion equation of the first longitudinal trajectory is:

[0047] f1(t)=a0×t 3 +b0×t 2 +c0t+d0;

[0048] the motion equation of the second longitudinal trajectory is:

[0049] f2(t)=a1×t 2 +b1×t+c1;

[0050] the motion equation of the third longitudinal trajectory is:

[0051] f3(t)=a2×t 3 +b2×t 2+c2xt+d2;

[0052] The motion equation of the fourth longitudinal trajectory is:

[0053] f4(t) = a3t + b3;

[0054] wherein f1(t) is the displacement of the ego vehicle at the t-th moment in the first longitudinal trajectory, f2(t) is the displacement of the ego vehicle at the t-th moment in the second longitudinal trajectory, f3(t) is the displacement of the ego vehicle at the t-th moment in the third longitudinal trajectory, f4(t) is the displacement of the ego vehicle at the t-th moment in the fourth longitudinal trajectory, a0, b0, c0, d0, a1, b1, c1, a2, b2, c2, d2, a3 and b3 are all parameters to be solved.

[0055] In some preferred embodiments of the second aspect, the control module solves the car-following model to obtain a solution result, including:

[0056] The control module solves the car-following model under the preset constraint condition to obtain the solution result.

[0057] The preset constraint condition includes: the longitudinal displacement of the connection position of the first longitudinal trajectory and the second longitudinal trajectory is continuous, the longitudinal velocity of the connection position of the first longitudinal trajectory and the second longitudinal trajectory is continuous, the longitudinal acceleration of the connection position of the first longitudinal trajectory and the second longitudinal trajectory is equal, the longitudinal displacement of the connection position of the second longitudinal trajectory and the third longitudinal trajectory is continuous, the longitudinal velocity of the connection position of the second longitudinal trajectory and the third longitudinal trajectory is continuous, the longitudinal acceleration of the connection position of the second longitudinal trajectory and the third longitudinal trajectory is equal, the longitudinal velocity of the third longitudinal trajectory at the end is the target speed, the longitudinal acceleration of the third longitudinal trajectory at the end is zero, the longitudinal displacement of the connection position of the third longitudinal trajectory and the fourth longitudinal trajectory is continuous, the longitudinal velocity of the connection position of the third longitudinal trajectory and the fourth longitudinal trajectory is continuous, the longitudinal acceleration variation rate of the first longitudinal trajectory and the second longitudinal trajectory is constant, and the total planning trajectory time length of the first longitudinal trajectory, the second longitudinal trajectory, the third longitudinal trajectory and the fourth longitudinal trajectory is a preset value.

[0058] In some preferred embodiments of the second aspect, the control module solves the car-following model to obtain a solution result, including:

[0059] The control module samples the solution result of the car-following model in a preset sampling interval to obtain the plurality of analytical solutions, and determines the plurality of analytical solutions as the solution result; wherein the sampling interval is [0, T], and T represents the total planning trajectory time length of the first longitudinal trajectory, the second longitudinal trajectory, the third longitudinal trajectory and the fourth longitudinal trajectory.

[0060] In some preferred embodiments of the second aspect, the control module controls the speed of the ego vehicle based on the solution result, comprising:

[0061] The control module calculates the cost of each analytical solution by a preset cost function, and selects the analytical solution with the minimum cost, and controls the speed of the ego vehicle based on the analytical solution with the minimum cost;

[0062] The preset cost function comprises:

[0063] f cost = w1 x cost speed + w2 x cost comfort + w3 x cost collision + w4 x cost centerAcc +

[0064] w5 x cost follow ;

[0065] cost speed = |f4(T)' - V s2 |;

[0066] cost comfort = |f2(t a )”|;

[0067]

[0068]

[0069] cost2 = V t x V t x k;

[0070]

[0071] cost3 = max(0, X t - X safet );

[0072] wherein f cost is the cost function, cost speed is the speed cost, cost comfort is the comfort cost, cost collision is the collision cost, cost centerAcc is the centripetal acceleration cost, cost follow is the stable following cost, w1, w2, w3, w4 and w5 are weights corresponding to the cost function, the speed cost, the comfort cost, the collision cost, the centripetal acceleration cost and the stable following cost respectively, k represents the lane curvature at the position of the ego vehicle, V trepresents the longitudinal speed of the ego vehicle at time t, X t represents the longitudinal displacement of the ego vehicle at time t, X tfront represents the longitudinal displacement of the front vehicle at time t, f4(t)' represents the longitudinal speed of the ego vehicle at the end of the fourth segment of the longitudinal trajectory, f2(t a represents the longitudinal acceleration at the beginning of the second segment of the longitudinal trajectory, V s is a second preset speed value, X safet represents the safety distance at time t, cost1, cost2 and cost3 are intermediate variables.

[0073] In some preferred embodiments of the second aspect, when the distance between the ego vehicle and the front vehicle is less than or equal to a preset distance, the target speed is the current speed of the front vehicle; when the distance between the ego vehicle and the front vehicle is greater than the preset distance, the target speed is a first preset speed value.

[0074] In some preferred embodiments of the second aspect, the speed control device further comprises an updating module, which is configured to perform golden section on the target speed to obtain an updated target speed when the current speed of the ego vehicle is greater than a preset speed limit value or the current acceleration of the ego vehicle is greater than a preset acceleration limit value.

[0075] The third aspect of the present application provides a terminal device, which comprises a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, wherein the processor implements the speed control method when executing the computer program.

[0076] The fourth aspect of the present application provides a computer readable storage medium, which comprises a stored computer program, wherein the computer readable storage medium controls the device where the computer readable storage medium is located to execute the speed control method when the computer program runs. BRIEF DESCRIPTION OF DRAWINGS

[0077] Figure 1 : a flowchart of a first embodiment of the speed planning method provided by the present application.

[0078] Figure 2 : a schematic diagram of a following vehicle scenario provided by the present application.

[0079] Figure 3 : a position curve diagram of the first embodiment of the speed planning method provided by the present application.

[0080] Figure 4 : a speed curve diagram of the first embodiment of the speed planning method provided by the present application.

[0081] Figure 5 : A schematic diagram of the acceleration curve of the first embodiment of the velocity planning method provided in this application.

[0082] Figure 6 This is a schematic diagram of an acceleration curve for an acceleration scenario provided in this invention application.

[0083] Figure 7 This is a schematic diagram of an acceleration curve for a deceleration scenario provided in this invention application.

[0084] Figure 8 : A schematic diagram of the structure of the first embodiment of the speed planning device provided in this application. Detailed Implementation

[0085] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0086] Example 1

[0087] Please refer to Figure 1 , Figure 1 A speed control method provided in this application includes steps S101 to S102; wherein,

[0088] Step S101: Under the condition of satisfying the safe distance between the vehicle and the vehicle in front, obtain the following model. The following model includes motion equations describing multiple longitudinal trajectories. The motion equations describe the relationship between the displacement and time of the vehicle on the longitudinal trajectory.

[0089] In this embodiment, the formula for calculating the safe distance is as follows:

[0090] X safe =t safe× V0+X min_safe (1)

[0091] Among them, X safe For a safe distance, V0 represents the vehicle's speed, and X... min_safe t represents the minimum following distance. safe Indicates the time parameter.

[0092] like Figure 2As shown, vehicle A is a self-vehicle, and vehicle B is a front vehicle. The self-vehicle needs to maintain a distance from the front vehicle, which is less than the safety distance. In some embodiments, the safety distance can be 100 meters, the time parameter can be 1 to 3 seconds, and the minimum distance can be 1 to 5 meters, which can be set by the automobile manufacturer or the driver.

[0093] In some automatic driving or assisted driving following scenarios, the self-vehicle needs to keep the distance from the front vehicle as close to the safety distance as possible through the following function. Since the speed and position of the front vehicle are dynamically changing, and even can be suddenly stopped, the speed needs to be controlled during the following process to ensure the safety and comfort of the user driving.

[0094] The multi-segment longitudinal trajectory includes a first segment longitudinal trajectory, a second segment longitudinal trajectory, a third segment longitudinal trajectory, and a fourth segment longitudinal trajectory. The acceleration change rate of the first segment longitudinal trajectory is equal to the acceleration change rate of the third segment longitudinal trajectory, and the acceleration of the second segment longitudinal trajectory and the acceleration of the fourth segment longitudinal trajectory are constant values.

[0095] The multi-segment longitudinal trajectory described in the embodiment has multiple control segment points in the following process. Compared with the control scheme of the existing technology using a quintic polynomial or a quartic polynomial, the starting and ending states are not only constrained, but also the self-vehicle state of each control segment point is constrained, ensuring the controllability of the starting state, the ending state, and the intermediate state during the following driving process of the self-vehicle. In addition, the multi-segment longitudinal trajectory includes a first segment longitudinal trajectory, a second segment longitudinal trajectory, a third segment longitudinal trajectory, and a fourth segment longitudinal trajectory. The acceleration change rate of the first segment longitudinal trajectory is equal to the acceleration change rate of the third segment longitudinal trajectory, and the acceleration of the second segment longitudinal trajectory and the acceleration of the fourth segment longitudinal trajectory are constant values. The speed transformation of the self-vehicle during the whole following driving process is relatively smooth, which optimizes the user experience and ensures the stability of the following driving.

[0096] As shown, Figures 3 to 5 As shown, Figure 3 is a position diagram (the longitudinal coordinate is the position or displacement) of the speed control method of the embodiment, Figure 4 is a speed diagram (the longitudinal coordinate is the speed) of the speed control method of the embodiment, Figure 5 is a speed diagram (the longitudinal coordinate is the acceleration) of the speed control method of the embodiment, Figures 3 to 5 The horizontal coordinates of the above diagrams are all time. Figure 5 The first segment acceleration curve, the second segment acceleration curve, the third segment acceleration curve, and the fourth segment acceleration curve in the diagram correspond to the first segment longitudinal trajectory, the second segment longitudinal trajectory, the third segment longitudinal trajectory, and the fourth segment longitudinal trajectory of the embodiment, respectively.

[0097] In some preferred embodiments, the following model specifically includes:

[0098] The motion equation of the first longitudinal trajectory is:

[0099] f1(t) = a0 x t 3 +b0 x t 2 +c0 t + d0; (2)

[0100] The motion equation of the second longitudinal trajectory is:

[0101] f2(t) = a1 x t 2 +b1 x t + c1; (3)

[0102] The motion equation of the third longitudinal trajectory is:

[0103] f3(t) = a2 x t 3 +b2 x t 2 +c2 x t + d2; (4)

[0104] The motion equation of the fourth longitudinal trajectory is:

[0105] f4(t) = a3 t + b3; (5)

[0106] wherein f1(t) is the displacement of the ego vehicle at the t time in the first longitudinal trajectory, f2(t) is the displacement of the ego vehicle at the t time in the second longitudinal trajectory, f3(t) is the displacement of the ego vehicle at the t time in the third longitudinal trajectory, and f4(t) is the displacement of the ego vehicle at the t time in the fourth longitudinal trajectory, a0, b0, c0, d0, a1, b1, c1, a2, b2, c2, d2, a3 and b3 are all to-be-solved parameters.

[0107] The step S102 obtains the above to-be-solved parameters and is used for speed control of the ego vehicle, so that the further smoothing of the speed change of the ego vehicle in the process of following the preceding vehicle is ensured, the refinement of the speed control in the process of following the preceding vehicle is improved, and the driving experience of the user is further optimized.

[0108] In step S102, the following model is solved to obtain a solving result, and the speed of the ego vehicle is controlled based on the solving result.

[0109] In some implementations, several constraints can be pre-set during the solution process of the car-following model to obtain more accurate results. For example, the pre-set constraints include: continuous longitudinal displacement at the junction of the first and second longitudinal trajectories; continuous longitudinal velocity at the junction of the first and second longitudinal trajectories; equal longitudinal acceleration at the junction of the first and second longitudinal trajectories; continuous longitudinal displacement at the junction of the second and third longitudinal trajectories; continuous longitudinal velocity at the junction of the second and third longitudinal trajectories; equal longitudinal acceleration at the junction of the second and third longitudinal trajectories; the longitudinal velocity at the end of the third longitudinal trajectories is the target velocity; the longitudinal acceleration at the end of the third longitudinal trajectories is zero; continuous longitudinal displacement at the junction of the third and fourth longitudinal trajectories; continuous longitudinal velocity at the junction of the third and fourth longitudinal trajectories; a constant rate of change of longitudinal acceleration for the first and second longitudinal trajectories; and a pre-set total planned trajectory time length for the first, second, third, and fourth longitudinal trajectories.

[0110] Combining the above content and formulas (2) to (5), the specific expression can be represented by the formula:

[0111] f1(0)=0;(6)

[0112] f1(0)'=V0;(7)

[0113] f1(0)”=0;(8)

[0114] f1(t a )=f2(t a (9)

[0115] f1(t a )'=f2(t a )';(10)

[0116] f1(t a )”=f2(t a (11)

[0117] f2(t a +t b )=f3(t a +t b (12)

[0118] f2(t a +t b )'=f3(t a +t b )';(13)

[0119] f2(ta +t b )”=f3(t a +t b (14)

[0120] f3(t a +t b +t a )'=V p (15)

[0121] f3(T)”=0;(16)

[0122] 2t a +t b +t c =T; (17)

[0123] f3(t a +t b +t a )=f4(t a +t b +t a (18)

[0124] f3(t a +t b +t a )'=f4(t a +b+t a )';(19)

[0125] -f1(0)”'=f2(t a +t b )”’=J;(20)

[0126] Where T is the total planned trajectory time length of the first, second, third, and fourth longitudinal trajectories, and t is... a Let t be the time interval between the first and third longitudinal trajectories. b Let t be the time of the second longitudinal trajectory segment. c The time for the fourth longitudinal trajectory segment is given, V0 is the initial velocity of the vehicle, J is a constant, and V p f3(t) is the current speed of the vehicle in front (when the distance between the vehicle and the vehicle in front is less than or equal to a preset distance). a +t b +t a )'=V p f1(0) represents the displacement of the vehicle at the start of the first longitudinal trajectory segment.

[0127] As known from the above, formula (6) indicates that the longitudinal displacement of the ego vehicle at the start time of the first longitudinal trajectory is 0 at t = 0 in the local coordinate system with the starting position of the ego vehicle as the origin. Formula (7) indicates that the start speed of the longitudinal trajectory of the ego vehicle is the actual longitudinal speed V0 of the ego vehicle, and V0 is known. Formula (8) indicates that the longitudinal acceleration of the ego vehicle at the starting position is 0. Formula (9) indicates that the longitudinal displacement at the connection position of the first longitudinal trajectory and the second longitudinal trajectory is continuous. Formula (10) indicates that the longitudinal speed at the connection position of the first longitudinal trajectory and the second longitudinal trajectory is continuous. Formula (11) indicates that the longitudinal acceleration at the connection position of the first longitudinal trajectory and the second longitudinal trajectory is equal. Formula (12) indicates that the longitudinal displacement at the connection position of the second longitudinal trajectory and the third longitudinal trajectory is continuous. Formula (13) indicates that the longitudinal speed at the connection position of the second longitudinal trajectory and the third longitudinal trajectory is continuous. Formula (14) indicates that the longitudinal acceleration at the connection position of the second longitudinal trajectory and the third longitudinal trajectory is equal. Formula (15) indicates that the longitudinal speed at the end time of the third longitudinal trajectory can be equal to the current speed V p of the target front vehicle in front of the ego vehicle. p Formula (16) indicates that the longitudinal acceleration at the end time of the third longitudinal trajectory is 0. Formula (17) indicates that the total planning trajectory time length T is known, which can be 8 seconds in some examples. Formula (18) indicates that the longitudinal displacement at the connection position of the third longitudinal trajectory and the fourth longitudinal trajectory is continuous. Formula (19) indicates that the longitudinal speed at the connection position of the third longitudinal trajectory and the fourth longitudinal trajectory is continuous. Formula (20) indicates that the jerk of the first longitudinal trajectory and the third longitudinal trajectory is a constant value J, and J is known to be 4, which has a physical meaning of indicating that the ego vehicle accelerates or decelerates to the desired value at the maximum jerk.

[0128] According to the above formula (15), when the distance between the ego vehicle and the front vehicle is less than or equal to a preset distance (for example, 100 meters), the target speed is the current speed V p of the front vehicle. When the distance between the ego vehicle and the front vehicle is greater than the preset distance, the target speed can be a first preset speed value V s1 , which can be set by the driver.

[0129] In other embodiments, when the equation solution does not satisfy the constraint, for example, when the current speed of the ego vehicle is greater than a preset speed limit, or the current acceleration of the ego vehicle is greater than a preset acceleration limit, the speed V0 of the ego vehicle and the speed V p of the front vehicle, or the speed V0 of the ego vehicle and the first preset speed value V s1 are too different; the target speed can be golden sectioned to obtain an updated target speed.

[0130] Exemplarily, the updating is performed according to the following formula: V p = V0 + (V p -V0)×0.618. Wherein V0 is the speed of the ego vehicle.

[0131] The target speed is iteratively updated through one or more times of the golden section above until the target speed meets the requirement, and the finally required target speed can be obtained.

[0132] In some preferred embodiments, the solving of the car-following model to obtain the solving result comprises: sampling the solving result of the car-following model in a preset sampling interval to obtain the multiple analytical solutions, and determining the multiple analytical solutions as the solving result; wherein the sampling interval is [0, T], and T represents the total planning trajectory time length of the first longitudinal trajectory, the second longitudinal trajectory, the third longitudinal trajectory and the fourth longitudinal trajectory.

[0133] Exemplarily, it is assumed that t a +t b +t a =T s , T s is unknown, then T s is sampled, the sampling point number is 30, the sampling interval is [0, T], and the physical meaning is that the ideal state must be reached at the planning time. At this time, multiple analytical solutions can be obtained, for example, in the acceleration scenario, the acceleration curve is as shown in Figure 6 , and in the deceleration scenario, the acceleration curve is as shown in Figure 7 .

[0134] In some preferred embodiments, the cost of each analytical solution can be calculated through a preset cost function, and the analytical solution with the minimum cost is selected, and the speed of the ego vehicle is controlled based on the analytical solution with the minimum cost.

[0135] The preset cost function comprises:

[0136] f cost = w1×cost speed + w2×cost comfort + w3×cost collision + w4×cost centerAcc +

[0137] w5×cost follow ;

[0138] cost speed = |f4(T)'-V s2 |;

[0139] costcomfort = |f2(t a ) | ;

[0140]

[0141] cost2 = V t × V t × k;

[0142]

[0143] cost3 = max(0, X t - X safet );

[0144] wherein f cost is the cost function, cost speed is the speed cost, cost comfort is the comfort cost, cost collision is the collision cost, cost centerAcc is the centripetal acceleration cost, cost follow is the stable following cost, w1, w2, w3, w4 and w5 are weights corresponding to the cost function, the speed cost, the comfort cost, the collision cost, the centripetal acceleration cost and the stable following cost respectively, k represents the lane curvature at the position of the ego vehicle, V t represents the longitudinal speed of the ego vehicle at time t, X t represents the longitudinal displacement of the ego vehicle at time t, X tfront represents the longitudinal displacement of the front vehicle at time t (if there is no front vehicle, the value can be -1000 meters), f4(T)' represents the longitudinal speed of the ego vehicle at the end of the fourth longitudinal trajectory, f2(t a ) represents the longitudinal acceleration at the beginning of the second longitudinal trajectory, V s2 is a second preset speed value, X safet represents the safety distance at time t, cost1, cost2 and cost3 are intermediate variables.

[0145] The lane curvature k at the position of the ego vehicle can be obtained through map data. The speed cost can be represented by the absolute value of the difference between the longitudinal speed of the ego vehicle at the end of the fourth longitudinal trajectory and the second preset speed value, which represents the cost of reaching the set speed. The comfort cost can be represented by the acceleration at time t a of the second longitudinal trajectory as the comfort cost of the analytical solution, and the greater the acceleration represents the greater the discomfort.

[0146] The cost of each analytical solution is obtained by the preset cost function, so that the analytical solution with the minimum cost is selected for speed control of the ego vehicle, which can consider speed, comfort, collision, centripetal acceleration and stable following, and ensure comfort, stability and low risk during following of the user.

[0147] As shown in Figure 8 The application further provides a speed control device 800, which comprises an acquisition module 801 and a control module 802.

[0148] The acquisition module 801 is configured to acquire a following model under the condition that the safety distance between the ego vehicle and the preceding vehicle is met, wherein the following model comprises a motion equation describing a plurality of longitudinal trajectories, and the motion equation describes the relationship between the displacement of the ego vehicle on the longitudinal trajectory and time.

[0149] The control module 802 is configured to solve the following model to obtain a solution result, and control the speed of the ego vehicle based on the solution result.

[0150] The plurality of longitudinal trajectories comprise a first longitudinal trajectory, a second longitudinal trajectory, a third longitudinal trajectory and a fourth longitudinal trajectory, the acceleration change rate of the first longitudinal trajectory is equal to the acceleration change rate of the third longitudinal trajectory, and the acceleration of the second longitudinal trajectory and the acceleration of the fourth longitudinal trajectory are constant values.

[0151] In some preferred technical solutions, the motion equation of the first longitudinal trajectory is:

[0152] f1(t)=a0×t 3 +b0×t 2 +c0t+d0;

[0153] The motion equation of the second longitudinal trajectory is:

[0154] f2(t)=a1×t 2 +b1×t+c1;

[0155] The motion equation of the third longitudinal trajectory is:

[0156] f3(t)=a2×t 3 +b2×t 2 +c2×t+d2;

[0157] The motion equation of the fourth longitudinal trajectory is:

[0158] f4(t)=a3t+b3;

[0159] Wherein, f1(t) is the displacement of the ego vehicle at the t th moment in the first longitudinal trajectory, f2(t) is the displacement of the ego vehicle at the t th moment in the second longitudinal trajectory, f3(t) is the displacement of the ego vehicle at the t th moment in the third longitudinal trajectory, f4(t) is the displacement of the ego vehicle at the t th moment in the fourth longitudinal trajectory, a0, b0, c0, d0, a1, b1, c1, a2, b2, c2, d2, a3 and b3 are all parameters to be solved.

[0160] In some preferred technical solutions, the control module 802 solves the car-following model to obtain a solution result, including:

[0161] The control module 802 solves the car-following model under the preset constraint condition to obtain the solution result.

[0162] The preset constraint condition includes: the longitudinal displacement of the connection position of the first longitudinal trajectory and the second longitudinal trajectory is continuous, the longitudinal velocity of the connection position of the first longitudinal trajectory and the second longitudinal trajectory is continuous, the longitudinal acceleration of the connection position of the first longitudinal trajectory and the second longitudinal trajectory is equal, the longitudinal displacement of the connection position of the second longitudinal trajectory and the third longitudinal trajectory is continuous, the longitudinal velocity of the connection position of the second longitudinal trajectory and the third longitudinal trajectory is continuous, the longitudinal acceleration of the connection position of the second longitudinal trajectory and the third longitudinal trajectory is equal, the longitudinal velocity of the third longitudinal trajectory at the end is the target speed, the longitudinal acceleration of the third longitudinal trajectory at the end is zero, the longitudinal displacement of the connection position of the third longitudinal trajectory and the fourth longitudinal trajectory is continuous, the longitudinal velocity of the connection position of the third longitudinal trajectory and the fourth longitudinal trajectory is continuous, the longitudinal acceleration variation rate of the first longitudinal trajectory and the second longitudinal trajectory is constant, and the total planning trajectory time length of the first longitudinal trajectory, the second longitudinal trajectory, the third longitudinal trajectory and the fourth longitudinal trajectory is a preset value.

[0163] In some preferred technical solutions, the control module 802 solves the car-following model to obtain a solution result, including:

[0164] The control module 802 samples the solution result of the car-following model in a preset sampling interval to obtain the plurality of analytical solutions, and determines the plurality of analytical solutions as the solution result; wherein, the sampling interval is [0, T], and T represents the total planning trajectory time length of the first longitudinal trajectory, the second longitudinal trajectory, the third longitudinal trajectory and the fourth longitudinal trajectory.

[0165] In some preferred technical solutions, the control module 802 controls the speed of the ego vehicle based on the solution result, including:

[0166] The control module 802 calculates the cost of each analytical solution by a preset cost function, selects an analytical solution with minimum cost, and controls the speed of the ego vehicle based on the analytical solution with minimum cost.

[0167] The preset cost function includes:

[0168] f cost = w1 x cost speed + w2 x cost comfort + w3 x cost collision + w4 x cost centerAcc +

[0169] w5 x cost follow ;

[0170] cost speed = |f4(T)' - V s2 | ;

[0171] cost comfort = |f2(t a )”| ;

[0172]

[0173] cost2 = V t x V t x k ;

[0174]

[0175] cost3 = max(0, X t - X safet ) ;

[0176] wherein f cost is the cost function, cost speed is the speed cost, cost comfort is the comfort cost, cost collision is the collision cost, cost centerAcc is the centripetal acceleration cost, cost follow is the stable following cost, w1, w2, w3, w4 and w5 are weights corresponding to the cost function, the speed cost, the comfort cost, the collision cost, the centripetal acceleration cost and the stable following cost respectively, k represents the lane curvature at the position of the ego vehicle, V t represents the longitudinal speed of the ego vehicle at t, X t represents the longitudinal displacement of the ego vehicle at t, X tfront represents the longitudinal displacement of the preceding vehicle at t, f4(T)' represents the longitudinal speed of the ego vehicle at the end of the fourth longitudinal trajectory, f2(t a) represents the longitudinal acceleration of the second segment longitudinal trajectory at the initial time, V s is a second preset speed value, X safet represents the safety distance at the t time, cost1, cost2 and cost3 are intermediate variables.

[0177] In some preferred technical solutions, when the distance between the ego vehicle and the front vehicle is less than or equal to a preset distance, the target speed is the current speed of the front vehicle; when the distance between the ego vehicle and the front vehicle is greater than the preset distance, the target speed is a first preset speed value.

[0178] In some preferred technical solutions, the speed control device 800 further comprises an updating module, which is configured to: when the current speed of the ego vehicle is greater than a preset speed limit value, or the current acceleration of the ego vehicle is greater than a preset acceleration limit value, perform golden section on the target speed to obtain an updated target speed.

[0179] In addition, the present application further provides a terminal device comprising a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, wherein the processor implements the speed control method when executing the computer program.

[0180] The processor can be a central processing unit (CPU), and can also be other general-purpose processors, digital signal processors (DSP), application specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor or the processor can also be any conventional processor or the like. The processor is the control center of the terminal, and is connected with various parts of the terminal through various interfaces and lines.

[0181] The memory can be used to store the computer program, and the processor realizes various functions of the terminal by running or executing the computer program stored in the memory and calling data stored in the memory. The memory can mainly include a program storage area and a data storage area, wherein the program storage area can store an operating system, at least one application program required by a function (such as a sound playing function, an image playing function, etc.), and the like; and the data storage area can store data created according to use of the mobile phone (such as audio data, a phone book, etc.), and the like. In addition, the memory can include a high-speed random access memory, and can also include a nonvolatile memory, for example, a hard disk, a memory, a plug-in hard disk, a SmartMedia Card (SMC), a Secure Digital (SD) card, a Flash Card, at least one disk storage device, a flash memory device, or other volatile solid-state memory devices.

[0182] Correspondingly, the present application further provides a computer readable storage medium, comprising a stored computer program, wherein the computer program controls a device where the computer readable storage medium is located to perform the speed control method when the computer program is running.

[0183] The modules integrated in the speed control device can be stored in a computer readable storage medium if they are realized in the form of software function units and sold or used as independent products. Based on this understanding, all or part of the processes in the above-mentioned embodiment methods can also be completed by a computer program instructing related hardware, and the computer program can be stored in a computer readable storage medium. The computer program can implement the steps of each method embodiment when executed by a processor. The computer program includes computer program code, which can be in the form of source code, object code, an executable file, or some intermediate form, etc. The computer readable medium can include any entity or device capable of carrying the computer program code, a recording medium, a U disk, a mobile hard disk, a magnetic disk, an optical disk, a computer memory, a read-only memory (ROM), a random access memory (RAM), an electrical carrier signal, a telecommunication signal, and a software distribution medium, etc.

[0184] Compared with the prior art, the embodiments of the present application have at least the following beneficial effects:

[0185] The application provides a speed control method, device, equipment and computer readable storage medium, the method comprises: obtaining a following model under the condition that the safety distance of a host vehicle and a preceding vehicle is met, the following model comprises a motion equation describing a plurality of longitudinal trajectories, and the motion equation describes the relationship between the displacement of the host vehicle on the longitudinal trajectory and time; solving the following model to obtain a solution; and controlling the speed of the host vehicle based on the solution; wherein the plurality of longitudinal trajectories comprises a first longitudinal trajectory, a second longitudinal trajectory, a third longitudinal trajectory and a fourth longitudinal trajectory; the acceleration change rate of the first longitudinal trajectory is equal to the acceleration change rate of the third longitudinal trajectory, and the acceleration of the second longitudinal trajectory and the acceleration of the fourth longitudinal trajectory are constant values. The following model of the application comprises the motion equation of the plurality of longitudinal trajectories, the motion equation describes the relationship between the displacement of the host vehicle on the longitudinal trajectory and time, by designing the plurality of longitudinal trajectories in the following model, that is, there are a plurality of control segment points in the following process, compared with the control scheme of the quintic polynomial or the quartic polynomial in the prior art, not only the initial and final states are constrained, but also the host vehicle state of each control segment point is constrained, ensuring the controllability of the initial state, the final state and the intermediate state in the following driving process of the host vehicle; in addition, the plurality of longitudinal trajectories comprises the first longitudinal trajectory, the second longitudinal trajectory, the third longitudinal trajectory and the fourth longitudinal trajectory, the acceleration change rate of the first longitudinal trajectory is equal to the acceleration change rate of the third longitudinal trajectory, and the acceleration of the second longitudinal trajectory and the acceleration of the fourth longitudinal trajectory are constant values, so that the speed transformation of the host vehicle in the whole following driving process is relatively smooth, the experience of the user is optimized, and the stability of the following driving is ensured.

[0186] The above-described specific embodiments further illustrate the purpose, technical solutions and advantages of the application, and it should be understood that the above-described specific embodiments are only specific embodiments of the application and are not used to limit the protection scope of the application. It should be particularly pointed out that any modification, equivalent replacement, improvement, etc. made by those skilled in the art within the spirit and principle of the application should be included in the protection scope of the application.

Claims

1. A speed control method characterized by, Comprise: Under the condition of meeting the safety distance of the ego vehicle and the front vehicle, a following vehicle model is obtained, the following vehicle model comprising a motion equation describing a multi-section longitudinal trajectory, the motion equation describing the relationship between the displacement of the ego vehicle on the longitudinal trajectory and time; The following vehicle model is solved to obtain a solution result; and the speed of the ego vehicle is controlled based on the solution result; Wherein, the multi-section longitudinal trajectory comprises a first section longitudinal trajectory, a second section longitudinal trajectory, a third section longitudinal trajectory and a fourth section longitudinal trajectory; the acceleration change rate of the first section longitudinal trajectory and the acceleration change rate of the third section longitudinal trajectory are equal, and the acceleration of the second section longitudinal trajectory and the acceleration of the fourth section longitudinal trajectory are constant values.

2. A speed control method as claimed in claim 1, characterized in that The motion equation of the first section longitudinal trajectory is: f1(t) = a0 x t 3 + b0 x t 2 + c0 t + d0; The motion equation of the second section longitudinal trajectory is: f2(t) = a1 x t 2 + b1 x t + c1; The motion equation of the third section longitudinal trajectory is: f3(t) = a2 x t 3 + b2 x t 2 + c2 x t + d2; The motion equation of the fourth section longitudinal trajectory is: f4(t)=a3t+b3; Wherein, f1(t) is the displacement of the ego vehicle at t time in the first section longitudinal trajectory, f2(t) is the displacement of the ego vehicle at t time in the second section longitudinal trajectory, f3(t) is the displacement of the ego vehicle at t time in the third section longitudinal trajectory, f4(t) is the displacement of the ego vehicle at t time in the fourth section longitudinal trajectory, a0, b0, c0, d0, a1, b1, c1, a2, b2, c2, d2, a3 and b3 are all to-be-solved parameters.

3. A speed control method as claimed in claim 2, characterized in that The following vehicle model is solved to obtain a solution result, comprising: Under a preset constraint condition, the following vehicle model is solved to obtain the solution result; The preset constraint condition comprises: the longitudinal displacement at the connection position of the first section longitudinal trajectory and the second section longitudinal trajectory is continuous, the longitudinal velocity at the connection position of the first section longitudinal trajectory and the second section longitudinal trajectory is continuous, the longitudinal acceleration at the connection position of the first section longitudinal trajectory and the second section longitudinal trajectory is equal, the longitudinal displacement at the connection position of the second section longitudinal trajectory and the third section longitudinal trajectory is continuous, the longitudinal velocity at the connection position of the second section longitudinal trajectory and the third section longitudinal trajectory is continuous, the longitudinal acceleration at the connection position of the second section longitudinal trajectory and the third section longitudinal trajectory is equal, the longitudinal velocity at the end of the third section longitudinal trajectory is the target speed, the longitudinal acceleration at the end of the third section longitudinal trajectory is zero, the longitudinal displacement at the connection position of the third section longitudinal trajectory and the fourth section longitudinal trajectory is continuous, the longitudinal velocity at the connection position of the third section longitudinal trajectory and the fourth section longitudinal trajectory is continuous, the longitudinal acceleration change rate of the first section longitudinal trajectory and the second section longitudinal trajectory is a constant value, and the total planning trajectory time length of the first section longitudinal trajectory, the second section longitudinal trajectory, the third section longitudinal trajectory and the fourth section longitudinal trajectory is a preset value.

4. A speed control method as claimed in claim 1, characterized in that The following vehicle model is solved to obtain a solution result, comprising: The solution result of the following vehicle model is sampled in a preset sampling interval to obtain a plurality of analytical solutions, and the plurality of analytical solutions are determined as the solution result; wherein, the sampling interval is [0, T], and T represents the total planning trajectory time length of the first section longitudinal trajectory, the second section longitudinal trajectory, the third section longitudinal trajectory and the fourth section longitudinal trajectory.

5. A speed control method as claimed in claim 4, characterized in that The speed of the ego vehicle is controlled based on the solving result, including: The cost of each analytical solution is calculated by a preset cost function, and the analytical solution with the minimum cost is selected, and the speed of the ego vehicle is controlled based on the analytical solution with the minimum cost; The preset cost function includes: f cost = w1 x cos t speed + w2 x cos t comfort + w3 x cos t collision + w4 x cos t centerAcc + w5 x cost follow ; cost speed = |f4(T)' - V s2 |; cost comfort = |f2(t a )”|; cost2 = V t × V t × k; cost3 = max(0, X t - X safet ) ; wherein f cost is the cost function, cost speed is the speed cost, cost comfort is the comfort cost, cost collision is the collision cost, cost centerAcc is the centripetal acceleration cost, cost follow is the stable following cost, w1, w2, w3, w4 and w5 are weights corresponding to the cost function, the speed cost, the comfort cost, the collision cost, the centripetal acceleration cost and the stable following cost respectively, k represents the lane curvature at the position of the ego vehicle, V t represents the longitudinal speed of the ego vehicle at time t, X t represents the longitudinal displacement of the ego vehicle at time t, X tfront represents the longitudinal displacement of the preceding vehicle at time t, f4(T)' represents the longitudinal speed of the ego vehicle at the end of the fourth longitudinal trajectory, f2(t a ) represents the longitudinal acceleration at the beginning of the second longitudinal trajectory, V s is a second preset speed value, X safet represents the safety distance at time t, cost1, cost2 and cost3 are intermediate variables.

6. A speed control method as claimed in claim 3, characterized in that The speed control method further includes: When the distance between the ego vehicle and the preceding vehicle is less than or equal to a preset distance, the target speed is the current speed of the preceding vehicle; When the distance between the ego vehicle and the preceding vehicle is greater than the preset distance, the target speed is a first preset speed value.

7. A speed control method as claimed in claim 3, characterized in that, The speed control method further includes: When the current speed of the ego vehicle is greater than a preset speed limit value, or the current acceleration of the ego vehicle is greater than a preset acceleration limit value; the target speed is golden sectioned to obtain an updated target speed.

8. A speed control device characterized by comprising: The speed control device includes an acquisition module and a control module; wherein, The acquisition module is configured to acquire a car-following model under the condition that the safety distance between the ego vehicle and the preceding vehicle is met, the car-following model including a motion equation describing a plurality of longitudinal trajectories, the motion equation describing the relationship between the displacement of the ego vehicle on the longitudinal trajectory and time; The control module is configured to solve the car-following model to obtain a solving result, and control the speed of the ego vehicle based on the solving result; The plurality of longitudinal trajectories include a first longitudinal trajectory, a second longitudinal trajectory, a third longitudinal trajectory, and a fourth longitudinal trajectory; the acceleration change rate of the first longitudinal trajectory is equal to the acceleration change rate of the third longitudinal trajectory, and the acceleration of the second longitudinal trajectory and the acceleration of the fourth longitudinal trajectory are constant values.

9. A terminal device, comprising: The computer readable storage medium includes a stored computer program, wherein when the computer program runs, the device where the computer readable storage medium is located executes the speed control method as claimed in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that, The computer readable storage medium includes a stored computer program, wherein when the computer program runs, the device where the computer readable storage medium is located executes the speed control method as claimed in any one of claims 1 to 7.

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