Control method for reverse driving of vehicle formation on obstructed road

Abstract

The present invention relates to a control method for a vehicle formation traveling in reverse on an obstructed road, and the method is characterized in that: on the basis of a pilot-follower formation model, a formation reverse driving control strategy based on the pilot vehicle trajectory is designed with the pilot vehicle gear position as a condition, and the front wheel steering angle control amount and speed control amount of the formation vehicles are calculated based on the geometric tracking method and the LQR theory respectively, to ensure consistency with the original trajectory of the pilot vehicle, and the distance between vehicles in the formation is within a reasonable range, so that the vehicle formation can achieve reverse driving under obstructed road conditions. Beneficial effects: The present invention takes into account the obstructed road conditions of vehicle formation driving, and proposes a reverse control method for formation driving, which has universal applicability. It can ensure the safety of the formation under the condition that the pilot vehicle enters an invalid road and needs to return to the original route, realize the overall reverse driving control of the formation, and improve the adaptability and practicality of the vehicle formation.

Description

Technical Field

[0001] The present invention belongs to the technical field of vehicle networking, and in particular relates to a control method for a vehicle formation traveling in the opposite direction on an obstructed road. Background Art

[0002] In recent years, the relevant technologies of cooperative vehicle infrastructure system (CVIS) have developed rapidly. Vehicles can sense and communicate with each other, and vehicles and roads, as well as roads and facilities on both sides, can also sense and communicate with each other. Under CVIS, combined with unmanned driving technology, it will surely promote the rapid development of unmanned vehicles and the transformation of traditional traffic flow. Unmanned vehicle platoon control has become one of the research focuses in this field. Vehicle platoon driving can improve the capacity and safety of road traffic, among which vehicle following control is the key issue of platoon driving.

[0003] Existing research mainly focuses on the control method of vehicle platoon forward driving, and there is less research on the control method of vehicle platoon reverse driving on obstructed roads. As an important part of the vehicle platoon driving function, the reverse driving of the vehicle platoon directly determines the practicality of the vehicle platoon driving technology. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the above-mentioned technology and provide a control method for the reverse driving of a vehicle formation on an obstructed road. The control strategy of the reverse driving of the formation based on the trajectory of the pilot vehicle is adopted to realize the overall reverse driving of the formation and improve the adaptability and practicality of the vehicle formation.

[0005] To achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a vehicle formation driving control method on an obstructed road, based on a pilot-follower formation model, taking the gear position of a pilot vehicle as a condition, a formation reverse driving control strategy based on the trajectory of the pilot vehicle is designed, and the front wheel steering angle control amount and speed control amount of the formation vehicles are calculated based on the geometric tracking method and the LQR theory respectively, to ensure that they are consistent with the original trajectory of the pilot vehicle and the distance between vehicles in the formation is within a reasonable range, so that the vehicle formation can achieve reverse driving under obstructed road conditions; the specific steps are as follows:

[0006] Step 1): The vehicle formation is completed, the pilot vehicle is numbered 0, and the remaining follower vehicles are numbered 1 to N. The formation has the function of autonomous forward driving;

[0007] Step 2): Use the vehicle-to-vehicle communication system to broadcast the position, heading angle, gear position, and speed of the formation vehicles;

[0008] Step 3): When the pilot car's gear position is not R, the following car records the driving status of the pilot car and returns to step 2); when the pilot car's gear position is R, execute step 4;

[0009] Step 4): Calculate the trajectory point with the smallest distance between the lead vehicle and the i-th following vehicle, and broadcast the sequence number of the trajectory point using the inter-vehicle communication system;

[0010] Step 5): Calculate the distance between the i-th following vehicle and the i+1-th following vehicle on the trajectory of the leading vehicle;

[0011] Step 6): Calculate the expected speed of the i-th following vehicle based on the LQR theory;

[0012] Step 7): Calculate the expected front wheel turning angle of the i-th following vehicle based on the geometric tracking method;

[0013] Step 8): Enter the vehicle driving status broadcast cycle, starting from step 2).

[0014] Further, in step 3), the following vehicle records the driving status of the pilot vehicle, specifically:

[0015] S21: The pilot vehicle trajectory is stored in a sequence, numbered starting from 1. The pilot vehicle trajectory is as follows:

[0016] T=[p1 p2 … p j ]

[0017] Among them, p j represents the jth trajectory point of the pilot vehicle;

[0018] S22: The single trajectory point of the pilot vehicle is as follows:

[0019] p j =[x j y j θ j ]

[0020] Among them, x j Represents the horizontal axis, y j represents the ordinate, θ j Indicates the heading angle;

[0021] Furthermore, in step 4), the trajectory point at which the distance between the pilot vehicle trajectory and the i-th following vehicle is the smallest is specifically:

[0022] S31: Calculation of the distance between the trajectory point of the leading vehicle and the i-th following vehicle:

[0023]

[0024] The meanings of the parameters in the formula are consistent with those in the S22 formula. i represents the horizontal coordinate of the i-th following vehicle, Y i represents the ordinate of the i-th following vehicle;

[0025] S32: Calculation of the minimum distance between the leading vehicle's trajectory and the i-th following vehicle:

[0026]

[0027] Among them, the meanings represented by the parameters in the formula are the same as those in the formula of S31. m i represents the serial number of the minimum distance trajectory point of the i-th following vehicle, and the serial number of this trajectory point is broadcast using the vehicle-to-vehicle communication system;

[0028] S33: The trajectory point with the minimum distance between the leading vehicle's trajectory and the i-th following vehicle is:

[0029]

[0030] Among them, the meanings represented by the parameters in the formula are the same as those in the formulas of S22 and S32.

[0031] Furthermore, in step 5), the distance between the i-th following vehicle and the (i + 1)-th following vehicle on the leading vehicle's trajectory is specifically:

[0032] S41: Calculation of the distance between the i-th following vehicle and the (i + 1)-th following vehicle on the leading vehicle's trajectory:

[0033]

[0034] Among them, the meanings represented by the parameters in the formula are the same as those in the formulas of S22 and S32;

[0035] Furthermore, in step 6), the calculation steps for the expected speed of the i-th following vehicle based on the LQR theory are as follows:

[0036] S51: When i = N, calculation of the expected speed:

[0037]

[0038] Among them, represents the speed threshold when reversing;

[0039] S52: When i < N, the states of the i-th following vehicle and the (i + 1)-th following vehicle are linearized as follows:

[0040]

[0041] Among them, u = [a i , A and B represent the Jacobian matrix, l d represents the expected distance between vehicles when reversing, V i and V i+1 respectively represent the speeds of the i-th following vehicle and the (i + 1)-th following vehicle, a irepresents the acceleration of the i-th following vehicle;

[0042] S53: The objective function of the optimal control is as follows:

[0043]

[0044] The meanings of the parameters in the formula are consistent with those in the S52 formula, and Q and R are weighted matrices in the optimization objective;

[0045] S54: Calculation of the expected speed of the i-th following vehicle:

[0046]

[0047] The meanings of the parameters in the formula are consistent with those in formulas S51 and S52;

[0048] Furthermore, in step 7), the expected front wheel turning angle of the i-th following vehicle is calculated as follows:

[0049] S61: Accumulate the length of the pilot vehicle's track:

[0050]

[0051] The meanings of the parameters in the formula are consistent with those in the formulas S22 and S32. i Indicates the upper limit of the accumulated sequence number;

[0052] S62: Comparison between accumulated length and preview length:

[0053]

[0054] The meanings of the parameters in the formula are consistent with those in the S61 formula. represents the preview length of the i-th following vehicle;

[0055] S63: Determine the desired target point:

[0056]

[0057] The meanings of the parameters in the formula are consistent with those in formulas S22 and S62;

[0058] S64: The expected front wheel turning angle of the i-th following vehicle is calculated by the following formula:

[0059]

[0060] The meanings of the parameters in the formula are consistent with those in formulas S63 and S52. i represents the wheelbase of the i-th following vehicle, X i and Yi Respectively represent the horizontal and vertical coordinates of the i-th following vehicle, Θ i represents the heading angle of the i-th following vehicle, k1 and k2 represent the control parameters respectively.

[0061] Beneficial effects: The present invention takes into account the obstructed road conditions of vehicle formation driving, and proposes a reverse driving control method for the obstructed road conditions of vehicle formation driving, which is universal. It can ensure the safety of the formation when the pilot vehicle enters an invalid road and needs to return to the original route, realize the overall reverse driving control of the formation, and improve the adaptability and practicality of the vehicle formation. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 It is a flow chart of the formation system implementation;

[0063] Figure 2 This is a schematic diagram of a vehicle formation traveling in reverse;

[0064] Figure 3 It is a schematic diagram of the global path of the leading vehicle and the following vehicle traveling in reverse;

[0065] Figure 4 It is a schematic diagram of a local enlarged portion 1 of the global path;

[0066] Figure 5 It is a schematic diagram of a local enlargement of the global path 2;

[0067] Figure 6 It is a schematic diagram of the path deviation between the following vehicle and the leading vehicle. DETAILED DESCRIPTION

[0068] In order to be able to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that, in the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other. In the following description, many specific details are set forth in order to fully understand the present invention, and the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the art without making creative work are within the scope of protection of the present invention. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by technicians in the technical field of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0069] See the attached drawings for details. This embodiment provides a control method for a vehicle formation to travel in the reverse direction on an obstructed road. Based on the pilot-follower formation model, a formation reverse travel control strategy based on the pilot vehicle trajectory is designed with the pilot vehicle gear position as a condition. The front wheel steering angle control amount and speed control amount of the formation vehicles are calculated based on the geometric tracking method and the LQR theory respectively to ensure that they are consistent with the original trajectory of the pilot vehicle and that the distance between vehicles in the formation is within a reasonable range, so that the vehicle formation can travel in the reverse direction under obstructed road conditions. The implementation process of the formation system is as follows: Figure 1 shown.

[0070] The specific implementation steps are as follows:

[0071] Step 1) The vehicle formation is completed, the lead vehicle is numbered 0, and the remaining follower vehicles are numbered 1 to N in sequence, and the formation has the function of autonomous forward driving;

[0072] Step 2) using the vehicle-to-vehicle communication system to broadcast the position, heading angle, gear position, and speed of the formation vehicles;

[0073] Step 3) When the pilot car's gear position is not R, the following car records the driving status of the pilot car and returns to step 2); when the pilot car's gear position is R, execute step 4;

[0074] Step 4) Calculate the trajectory point with the smallest distance between the lead vehicle and the i-th following vehicle, and broadcast the sequence number of the trajectory point using the inter-vehicle communication system;

[0075] Step 5) Calculate the distance between the ith following vehicle and the (i+1)th following vehicle on the trajectory of the pilot vehicle;

[0076] Step 6) Calculate the expected speed of the i-th following vehicle based on the LQR theory;

[0077] Step 7) calculating the expected front wheel turning angle of the i-th following vehicle based on the geometric tracking method;

[0078] Step 8) Enter the vehicle driving status broadcast cycle, starting gradually from step 2).

[0079] The preferred solution of this embodiment is that the step 3) is specifically:

[0080] S21: The driving status of the pilot car is stored in a sequence, starting from 1, and gradually forming a set T, which is the pilot car trajectory. The following car receives the driving status information of the pilot car through the inter-vehicle communication system and stores it at intervals of 0.1 seconds. The pilot car trajectory is as follows:

[0081] T=[p1 p2 ... p j ]

[0082] Among them, p j represents the jth trajectory point of the pilot vehicle;

[0083] S22: The single trajectory point of the pilot vehicle is as follows:

[0084] p j =[x j y j θ j ]

[0085] Among them, x j Represents the horizontal axis, y j represents the ordinate, θ j Indicates the heading angle;

[0086] The preferred solution of this embodiment is that in step 4), the trajectory point with the smallest distance between the pilot vehicle and the i-th following vehicle is traversed through all trajectory points of the pilot vehicle, the distance between each trajectory point and the i-th following vehicle is calculated, the minimum distance is obtained by comparison, and m is used i Indicates the sequence number of the minimum distance trajectory point, specifically:

[0087] S31: Calculation of the distance between the trajectory point of the leading vehicle and the i-th following vehicle:

[0088]

[0089] The meanings of the parameters in the formula are consistent with those in the S22 formula. i represents the horizontal coordinate of the i-th following vehicle, Y i represents the ordinate of the i-th following vehicle;

[0090] S32: Calculation of the minimum distance between the leader vehicle trajectory and the i-th following vehicle:

[0091]

[0092] The meanings of the parameters in the formula are consistent with those in the S31 formula, m i Indicates the minimum distance trajectory point number of the i-th following vehicle, and the trajectory point number is broadcasted by the vehicle-to-vehicle communication system;

[0093] S33: The trajectory point with the minimum distance between the leader vehicle and the i-th following vehicle is:

[0094]

[0095] The meanings of the parameters in the formula are consistent with those in formulas S22 and S32.

[0096] In the preferred solution of this embodiment, in step 5), the distance between adjacent following vehicles in the formation is represented by the cumulative distance of the trajectory points closest to the two following vehicles, which can accurately reflect the states of the two following vehicles relative to the leading vehicle; calculating the distance directly using the positions of the two following vehicles only reflects the relative distance between the two vehicles and cannot reflect their states in the formation. m i and m i+1 respectively represent the sequence numbers of the points with the minimum distance of the i-th following vehicle and the (i + 1)-th following vehicle on the leading vehicle's trajectory. By accumulating the distances between adjacent points between the two sequence numbers, the distance between the two following vehicles on the leading vehicle's trajectory can be obtained; the larger the number of the vehicle in the formation, the smaller the sequence number of the corresponding point on the leading vehicle's trajectory with the minimum distance. The distance between the i-th following vehicle and the (i + 1)-th following vehicle on the leading vehicle's trajectory is specifically:

[0097] S41: Calculation of the distance between the i-th following vehicle and the (i + 1)-th following vehicle on the leading vehicle's trajectory:

[0098]

[0099] where the meanings of the parameters in the formula are the same as those in the formulas of S22 and S32;

[0100] In the preferred solution of this embodiment, in step 6), the LQR theory is a widely used modern control method. When the formation is reversing, the present invention linearizes the distance and speed states of adjacent following vehicles, designs an optimal control objective function, and obtains the optimal linear negative feedback K by adjusting the weights of the distance and speed, and then obtains the desired acceleration and desired speed. The calculation steps for calculating the desired speed of the i-th following vehicle based on the LQR theory are as follows:

[0101] S51: When i = N, calculation of the desired speed:

[0102]

[0103] where, represents the speed threshold when reversing;

[0104] S52: When i < N, the states of the i-th following vehicle and the (i + 1)-th following vehicle are linearized as follows:

[0105]

[0106] where, u = [a i , A and B represent the Jacobian matrices, B = [0 1] T , l d represents the desired spacing between vehicles when reversing, V i and V i+1They represent the speeds of the i-th following car and the i+1-th following car, respectively. i represents the acceleration of the i-th following vehicle;

[0107] S53: The objective function of the optimal control is as follows:

[0108]

[0109] The parameters in the formula have the same meaning as those in the S52 formula. Q and R are weighted matrices in the optimization objective. The optimization objective is to stabilize the system state to the desired distance and the speed of the i+1th following vehicle, and obtain the control rate u=-Kx of LQR, which is the desired acceleration of the following vehicle.

[0110] Where K = R -1 B -1 P, solution of matrix P: A T P+PA-PBR -1 B T P+Q=0.

[0111] S54: Calculation of the expected speed of the i-th following vehicle:

[0112]

[0113] The meanings of the parameters in the formula are consistent with those in formulas S51 and S52;

[0114] The preferred solution of this embodiment is that in step 7), the front wheel angle controller is designed based on the geometric tracking method. The geometric tracking method is a nonlinear feedback function based on the lateral tracking error, and can achieve the lateral tracking error exponential convergence to 0. The control amount of the vehicle's front wheel angle can be intuitively obtained based on the relative geometric relationship between the vehicle posture and the desired target point. The desired target point is determined based on the preview length, starting from the i-th follower vehicle at the minimum point of the pilot vehicle's track, and accumulating the distance between adjacent track points. When the accumulated length is greater than or equal to the preview distance, the accumulated last track point is the desired target point.

[0115] The calculation steps for the i-th following expected front wheel turning angle are as follows:

[0116] S61: Accumulate the length of the pilot vehicle's track:

[0117]

[0118] The meanings of the parameters in the formula are consistent with those in the formulas S22 and S32. i Indicates the upper limit of the accumulated sequence number;

[0119] S62: Comparison between accumulated length and preview length:

[0120]

[0121] The meanings of the parameters in the formula are consistent with those in the S61 formula. represents the preview length of the i-th following vehicle;

[0122] S63: Determine the desired target point:

[0123]

[0124] The meanings of the parameters in the formula are consistent with those in formulas S22 and S62;

[0125] S64: The expected front wheel turning angle of the i-th following vehicle is calculated by the following formula:

[0126]

[0127] The meanings of the parameters in the formula are consistent with those in formulas S63 and S52. i represents the wheelbase of the i-th following vehicle, X i and Y i Respectively represent the horizontal and vertical coordinates of the i-th following vehicle, Θ i represents the heading angle of the i-th following vehicle, k1 and k2 represent the control parameters respectively.

[0128] Example 1

[0129] The control method process of the vehicle formation driving in the opposite direction on the obstructed road is described in detail:

[0130] Based on the pilot-follower formation model, this embodiment designs a reverse driving control strategy for the formation based on the pilot vehicle trajectory, taking the pilot vehicle gear position as a condition. The front wheel steering angle control amount and speed control amount of the formation vehicles are calculated based on the geometric tracking method and LQR theory respectively, ensuring that they are consistent with the original trajectory of the pilot vehicle, and the distance between vehicles in the formation is within a reasonable range, so that the vehicle formation can achieve reverse driving under obstructed road conditions. This embodiment uses Matlab / Simulink to build a simulation platform, the simulation test environment is Inter Corei7, 2.30GHz processor, Windows 10 operating system, and the simulation software is MatlabR2018b. The vehicle formation consists of 1 pilot vehicle I and 3 follower vehicles II, with a step size of 0.1s.

[0131] 1. Experimental design and parameter setting

[0132] The function expression of the pilot vehicle's driving trajectory is as follows:

[0133]

[0134] Where ω represents the yaw rate of the pilot vehicle and t represents the time.

[0135] Assume that a pilot car and three follower cars form a formation to achieve the following driving of the formation. The initial position of the pilot car is (0,0) and the initial heading is 0. Assume that the pilot car drives at a variable speed for 150 seconds, and at the moment of 150 seconds, the speed of the pilot car is reduced to zero, and the driver switches the gear of the pilot car to R gear. When the first follower car starts to reverse, the driver operates the pilot car to reverse.

[0136] 2. Instantaneous Calculation Process

[0137] The vehicle platooning system is as follows: Figure 1 As shown, taking the following vehicle 1 as an example, the calculation process at the moment of 150s is described to implement the steps of the present invention.

[0138] S21: The driving status of the pilot car is stored in a sequence, starting from 1, and gradually forming a set T, which is the pilot car trajectory. The following car receives the driving status information of the pilot car through the inter-vehicle communication system and stores it at intervals of 0.1 seconds. The pilot car trajectory is as follows:

[0139] T=[p1 p2 ... p j ]

[0140] Among them, p j represents the jth trajectory point of the pilot car, with a total of 1500 trajectory points recorded;

[0141] S22: The single trajectory point of the pilot vehicle is as follows:

[0142] p j =[x j y j θ j ]

[0143] Among them, x j Represents the horizontal axis, y j represents the ordinate, θ j Indicates the heading angle, the 1500th trajectory point is p 1500 =[-19.21 -58.65 2.51];

[0144] The trajectory of the pilot car is the point with the smallest distance from the i-th following car. All the trajectory points of the pilot car are traversed, and the distance between each trajectory point and the i-th following car is calculated. The minimum distance is obtained by comparison, and m i Indicates the sequence number of the minimum distance trajectory point, specifically:

[0145] S31: Calculation of the distance between the lead vehicle's trajectory point and the first following vehicle:

[0146]

[0147] The meanings of the parameters in the formula are consistent with those in the S22 formula. i represents the horizontal coordinate of the i-th following vehicle, Y i represents the ordinate of the i-th following vehicle, X i and Y i The values ​​are -15.17 and -61.59 respectively, p 1500 =[-19.21 -58.65 2.51], The value is 4.996;

[0148] S32: Calculation of the minimum distance between the lead vehicle trajectory and the first following vehicle:

[0149]

[0150] The meanings of the parameters in the formula are consistent with those in the S31 formula, m i represents the minimum distance trajectory point number of the i-th following vehicle. The trajectory point number is broadcasted by the vehicle-to-vehicle communication system. By traversing all the trajectory points of the pilot vehicle, the 1480th trajectory point p is obtained. 1480 =[-15.09 -61.63 2.51], the distance to the first following vehicle is 0.089, which is the closest track point, then m 1 =1480;

[0151] S33: The trajectory point where the distance between the leading vehicle and the first following vehicle is the smallest is:

[0152]

[0153] The meanings of the parameters in the formula are consistent with those in the formulas S22 and S32, so p 1480 =[-15.09-61.63 2.51].

[0154] The distance between adjacent following vehicles in the formation is expressed by the cumulative distance of the closest trajectory points to the two following vehicles, which can accurately reflect the status of the two following vehicles relative to the lead vehicle; directly calculating the distance using the positions of the two following vehicles only reflects the relative distance between the two vehicles, but cannot reflect their status in the formation. i and m i+1 They represent the sequence numbers of the minimum distance points between the i-th following vehicle and the i+1-th following vehicle on the leader vehicle's track. By accumulating the distances between the adjacent points of the two sequence numbers, the distance between the two following vehicles on the leader vehicle's track can be obtained. The larger the number of the vehicle in the formation, the smaller the sequence number of the minimum distance point on the leader vehicle's track. The distance between the i-th following vehicle and the i+1-th following vehicle on the leader vehicle's track is specifically:

[0155] S41: Calculation of the distance between the first following vehicle and the second following vehicle on the lead vehicle's trajectory:

[0156]

[0157] Among them, the meanings represented by the parameters in the formula are the same as those in the formulas of S22 and S32. From step 4), the serial number of the trajectory point with the minimum distance between the lead vehicle's trajectory and the second following vehicle is m 2 = 1461, that is, p 1461 = [-11.15 -64.45 2.52], and the value obtained through cumulative calculation is 4.81;

[0158] The LQR theory is a widely applied modern control method. In the present invention, when performing formation reverse driving, the distance and speed states between adjacent following vehicles are linearized, and an optimal control objective function is designed. By adjusting the weights of the distance and speed, the optimal linear negative feedback K is obtained, and then the expected acceleration and expected speed are obtained. The calculation steps for the expected speed of the i-th following vehicle based on the LQR theory are as follows. Since i = 1 and N = 3, S52 is performed:

[0159] S52: When i < N, the states of the first following vehicle and the second following vehicle are linearized as follows:

[0160]

[0161] Among them, u = [a i , A and B represent the Jacobian matrix, B = [0 1] T , l d represents the expected spacing between vehicles during reverse driving, with a value of 4.5, V i and V i+1 respectively represent the speeds of the i-th following vehicle and the (i + 1)-th following vehicle, both with a value of zero, and a i represents the acceleration of the i-th following vehicle, then x = [0.31 0].

[0162] S53: The objective function of the optimal control is as follows:

[0163]

[0164] Among them, the meanings represented by the parameters in the formula are the same as those in the formula of S52. Q and R are the weighting matrices in the optimization objective, R = [1]. The optimization objective stabilizes the system state to the expected distance and the speed of the (i + 1)-th following vehicle, and the control rate u = -Kx of the LQR is obtained, which is the expected acceleration of the following vehicle, then u = 3.1, that is, the numerical value of the expected acceleration is 3.1;

[0165] S54: Calculation of the expected speed of the first following vehicle:

[0166] V i d =u+V i

[0167] The meanings of the parameters in the formula are consistent with those in formulas S51 and S52, that is, V i d =3.1;

[0168] The front wheel steering controller is designed based on the geometric tracking method. The geometric tracking method is a nonlinear feedback function based on the lateral tracking error, and can achieve the exponential convergence of the lateral tracking error to 0. The control amount of the vehicle's front wheel steering angle can be intuitively obtained based on the relative geometric relationship between the vehicle posture and the desired target point. The desired target point is determined based on the preview length. Starting from the point where the i-th follower vehicle has the minimum distance from the leader vehicle's track, the distance between adjacent track points is accumulated. When the accumulated length is greater than or equal to the preview distance, the accumulated last track point is the desired target point.

[0169] The calculation steps for the first following desired front wheel turning angle are as follows:

[0170] S61: Accumulate the length of the pilot vehicle's track:

[0171]

[0172] The meanings of the parameters in the formula are consistent with those in the formulas S22 and S32. i Indicates the upper limit of the accumulated sequence number, where m 1 =1480;

[0173] S62: Comparison between accumulated length and preview length:

[0174]

[0175] The meanings of the parameters in the formula are consistent with those in the S61 formula. represents the preview length of the i-th following vehicle, and its value is 6.0. Then, by accumulating and comparing, we can get r 1 =1456;

[0176] S63: Determine the desired target point:

[0177]

[0178] The meanings of the parameters in the formula are consistent with those in the formulas S22 and S62. 1456 =[-10.11 -65.19 2.52];

[0179] S64: The expected front wheel turning angle of the first following vehicle is calculated by the following formula:

[0180]

[0181] The meanings of the parameters in the formula are consistent with those in formulas S63 and S52. i Indicates the wheelbase of the i-th following vehicle, the value is 2, X i and Y i They represent the horizontal and vertical coordinates of the i-th following vehicle, and their values ​​are -15.17 and -61.59 respectively. i represents the heading angle of the i-th following vehicle, with a value of 2.51. k1 and k2 represent control parameters, with values ​​of 1 and 0.25 respectively. The expected front wheel steering angle is -0.3994 rad.

[0182] The global path of a platoon consisting of a leader vehicle and three follower vehicles traveling in reverse is as follows: Figure 3 As shown, the local enlargement is as follows Figure 4 and Figure 5 As shown in the figure, the lead vehicle turns right from (0,0) to (-19.21,-58.65). There is no passable road ahead, so the vehicle formation needs to drive in the opposite direction to the starting point (0,0). During the reverse driving process, the maximum lateral deviations of the trajectories of the three following vehicles and the lead vehicle are 0.08m, 0.26m, and 0.56m, respectively. Figure 6 shown.

[0183] The above reference embodiment provides a detailed description of the control method for a vehicle formation traveling in the opposite direction on an obstructed road, which is illustrative rather than restrictive, and several embodiments may be listed according to the limited scope. Therefore, changes and modifications without departing from the overall concept of the present invention should fall within the scope of protection of the present invention.

Claims

1. A control method for a vehicle formation traveling in the opposite direction on an obstructed road, characterized in that: Based on the leader-follower formation model, with the gear of the leader vehicle as a condition, a formation reverse driving control strategy based on the leader vehicle's trajectory is proposed. The front-wheel steering angle control amount and speed control amount of the formation vehicles are calculated respectively based on the geometric tracking method and LQR theory to ensure consistency with the original trajectory of the leader vehicle, enabling the vehicle formation to reverse under blocked road conditions. The specific steps are as follows: Step 1): The vehicle formation is completed. The leader vehicle is numbered 0, and the remaining follower vehicles are numbered 1 to N in sequence. The formation has the function of autonomous forward driving. Step 2): Use the vehicle-to-vehicle communication system to broadcast the positions, heading angles, gears, and speeds of the formation vehicles. Step 3): When the gear of the leader vehicle is not R, the follower vehicles record the driving state of the leader vehicle and return to Step 2); when the gear of the leader vehicle is R, execute Step 4). Step 4): Calculate the trajectory point on the leader vehicle's trajectory that is closest to the i-th follower vehicle, and broadcast the serial number of this trajectory point. Step 5): Calculate the distance between the i-th follower vehicle and the (i + 1)-th follower vehicle on the leader vehicle's trajectory. Step 6): Calculate the expected speed of the i-th follower vehicle based on LQR theory. Step 7): Calculate the expected front-wheel steering angle of the i-th follower vehicle based on the geometric tracking method. Step 8): Enter the vehicle driving state broadcast period, starting from Step 2 gradually. The calculation steps for the expected speed of the i-th follower vehicle in Step 6) based on LQR theory are as follows: S51: When i = N, calculate the expected speed: in, Indicates the speed threshold when driving in reverse; S52: When i < N, linearize the states of the i-th follower vehicle and the (i + 1)-th follower vehicle as follows: in, u=[a i ], A and B represent Jacobian matrices, l d Represents the expected distance between vehicles when reversing, V i and V i+1 They represent the speeds of the i-th following car and the i+1-th following car, respectively. i represents the acceleration of the i-th following vehicle; S53: The objective function of the optimal control is as follows: Among them, the meanings of the parameters in the formula are the same as those in the formula of S52, and Q and R are the weighting matrices in the optimization objective. S54: Calculate the expected speed of the i-th follower vehicle: Among them, the meanings of the parameters in the formula are the same as those in the formulas of S51 and S52. The calculation steps for the expected front-wheel steering angle of the i-th follower vehicle in Step 7) are as follows: S61: Accumulate the length of the leader vehicle's trajectory: The meanings of the parameters in the formula are consistent with those in the formulas S22 and S32. i Indicates the upper limit of the accumulated sequence number; S62: Compare the accumulated length with the preview length: The meanings of the parameters in the formula are consistent with those in the S61 formula. represents the preview length of the i-th following vehicle; S63: Determine the expected target point: Among them, the meanings of the parameters in the formula are the same as those in the formulas of S22 and S62. S64: Calculate the expected front-wheel steering angle of the i-th follower vehicle by the following formula: The meanings of the parameters in the formula are consistent with those in formulas S63 and S52. i represents the wheelbase of the i-th following vehicle, X i and Y i Respectively represent the horizontal and vertical coordinates of the i-th following vehicle, Θ i represents the heading angle of the i-th following vehicle, k1 and k2 represent the control parameters respectively.

2. The control method according to claim 1 is characterized in that: What the follower vehicle in Step 3) records about the driving state of the leader vehicle is specifically: S21: The leader vehicle's trajectory is stored in sequence, starting from number 1. The leader vehicle's trajectory is as follows: T=[p1 p2…p j ] Among them, p j represents the jth trajectory point of the pilot vehicle; S22: A single trajectory point of the leader vehicle is as follows: p j [x j y j θ j ] Among them, x j Represents the horizontal axis, y j represents the ordinate, θ j Indicates the heading angle.

3. The control method according to claim 2 is characterized in that: What the trajectory point on the leader vehicle's trajectory closest to the i-th follower vehicle in Step 4) is specifically: S31: Calculate the distance between the leader vehicle's trajectory point and the i-th follower vehicle: The meanings of the parameters in the formula are consistent with those in the S22 formula. i represents the horizontal coordinate of the i-th following vehicle, Y i represents the ordinate of the i-th following vehicle; S32: Calculate the minimum distance between the leader vehicle's trajectory and the i-th follower vehicle: The meanings of the parameters in the formula are consistent with those in the S31 formula, m i Indicates the sequence number of the minimum distance trajectory point of the i-th following vehicle, and the sequence number of the trajectory point is broadcasted by the vehicle-to-vehicle communication system; S33: The trajectory point on the leader vehicle's trajectory with the minimum distance from the i-th follower vehicle is: Among them, the meanings of the parameters in the formula are the same as those in the formulas of S22 and S32.

4. The control method according to claim 3 is characterized in that: What the distance between the i-th follower vehicle and the (i + 1)-th follower vehicle on the leader vehicle's trajectory in Step 5) is specifically: S41: Calculate the distance between the i-th follower vehicle and the (i + 1)-th follower vehicle on the leader vehicle's trajectory: The meanings of the parameters in the formula are consistent with those in formulas S22 and S32.

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