An event-triggered communication and control method for platooning

Abstract

The present invention relates to an event-triggered communication and control method for platoon driving, comprising the following steps: S1, setting a convoy consisting of N vehicles, installing an event-triggered communication module and an event-triggered control module on each vehicle; S2, checking whether the communication of the self-vehicle meets the triggering condition at a fixed sampling period, if so, executing step S3; if not, executing step S4; S3, the self-vehicle sends status information to the neighboring vehicle; S4, the neighboring vehicle uses the self-vehicle status information at the previous sending moment to predict the self-vehicle status at the current moment; S5, checking whether the self-vehicle control meets the triggering condition at a fixed sampling period, if so, executing step S6; if not, executing step S7; S6, the self-vehicle sends a new control signal to the engine and executes it; S7, the control signal of the self-vehicle remains unchanged. Compared with the prior art, the present invention can synchronize the speed and acceleration of all vehicles in different initial states and arrange them in sequence at a preset vehicle spacing.

Description

Technical Field

[0001] The present invention relates to the field of vehicle networking and vehicle-mounted control technology, and in particular to an event-triggered communication and control method for platoon driving. Background Art

[0002] On December 30, 2019, the First Launch Group collaborated with TuSimple, Huawei and other partners to conduct a platoon demonstration on the Beijing-Li Expressway Smart Highway, combining autonomous driving with C-V2X vehicle-road collaboration technology. The test results show that the vehicle platoon can achieve the technical indicator of maintaining a distance of 10m between vehicles at a speed of 80km / h, which is highly competitive in saving fuel, reducing road occupancy, and reducing transportation costs. Vehicle platooning is a key technology for the next generation of intelligent transportation systems. The use of C-V2X wireless communication technology to complete real-time dynamic information interaction and fully realize efficient collaboration between vehicles is of great significance to ensuring driving safety and improving traffic efficiency. In the face of the high reliability, low latency, and high mobility requirements of the dedicated vehicle-road collaboration communication system, radio waves need to have good transmission characteristics and achieve continuous wide-area coverage. Such application scenarios often require the use of radio waves in the frequency band below 3GHz to complete. Due to the slow generational upgrade of communication networks, the frequency band below 3GHz includes the spectrum of 2G, 3G, and 4G currently used in the current network, and the continuous spectrum that can be allocated to 5G is in short supply. Moreover, the power consumption of a single 5G station is 2.5 to 3.5 times that of a single 4G station, and the energy consumption cost of the communication network accounts for about 20% of the network maintenance cost. With the deployment and application of 5G mobile communication systems, the demand for spectrum resources in the Internet of Vehicles will increase significantly. As a non-renewable basic strategic resource, spectrum resources are facing huge gaps and pressures. The event trigger mechanism can effectively save the network bandwidth of the Internet of Vehicles and the energy consumption of terminal devices, avoiding the waste of spectrum resources caused by continuous communication. It is of great significance to improve the utilization of spectrum and reduce communication costs, and has good application prospects in bandwidth-constrained scenarios.

[0003] The event trigger mechanism refers to a communication strategy that triggers data transmission based on the occurrence of an event. It has become a hot topic in the field of multi-agent systems. For example, relevant literature applies the dynamic event trigger mechanism to vehicle platoon driving and analyzes the string stability of the fleet. However, the dynamic event trigger mechanism is complex to design and has many parameters. It is difficult for engineers to quickly master its debugging method, which is limited in practical application. Or by calculating the state difference between the current moment and the adjacent trigger moment and the state difference between the previous trigger moment and the adjacent trigger moment, it is determined whether the current moment is the sending moment, and by solving the LMI problem, sufficient conditions are given to ensure the global stability of the fleet. However, when new vehicles join the fleet and when the communication topology of the fleet is disturbed and changed, the above methods all need to adjust the controller gains of all vehicles in the fleet to adapt to these changes. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and to provide an efficient and easy-to-implement event-triggered communication and control method for platoon driving.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] An event-triggered communication and control method for platoon driving, comprising the following steps:

[0007] S1. Set up a connected fleet consisting of N vehicles, and install an event-triggered communication module and an event-triggered control module on each vehicle;

[0008] S2, the vehicle's event-triggered communication module checks whether the vehicle communication meets the triggering condition at a fixed sampling period, if so, execute step S3; if not, execute step S4;

[0009] S3, the vehicle sends status information to the neighboring vehicle;

[0010] S4, the neighboring vehicle uses the vehicle state information at the previous sending time to predict the vehicle state at the current time;

[0011] S5, the vehicle event trigger control module uses the state information to construct an adaptive control law, and checks whether the vehicle control meets the trigger condition at a fixed sampling period. If so, execute step S6; if not, execute step S7;

[0012] S6, the vehicle sends a new control signal to the engine and executes it;

[0013] S7. The control signal of the vehicle remains unchanged.

[0014] Furthermore, in step S2, the event-triggered communication module of the vehicle constructs a longitudinal dynamics model of the vehicle, sets an evolution model and motion state of the virtual navigator, and checks whether the self-vehicle communication meets the triggering conditions at a fixed sampling period.

[0015] Furthermore, the longitudinal dynamics model of the ith vehicle in the event-triggered communication module is expressed as:

[0016]

[0017] Among them, x i (t) = [p i ,v i ,a i ] T is the state vector, p i is the position, v i is the speed, a i is the acceleration, u i(t) is the control signal, A is the system matrix, b is the vector, and Where τ>0 is the engine time constant;

[0018] Vehicle i (i = 1…N) controls input u i (t), the state x of vehicle i i (t) Following the state x of the virtual navigator 0 (t) changes, x 0 (t) In the lead vehicle i=1, according to the set initial condition x 0 (0) is calculated, and its evolution model is expressed as:

[0019]

[0020] Among them, x 0 (t) is the state of the virtual navigator, u 0 (t) is the control input of the virtual navigator, which is adjusted by u 0 (t) to control x 0 (t), the virtual navigator is the object to be tracked by all vehicles in the convoy. The goal of all vehicles is to keep the speed and acceleration consistent with the virtual navigator, and to keep a certain formation with the navigator;

[0021] For vehicle i in the fleet, check the current time t and its previous sending time Poor exercise status Whether the norm of exceeds a time-decayed dynamic threshold, if not, vehicle i does not send a signal to its neighbor vehicle j∈Ω at the current time t i Send status information x i (t); if it exceeds, the vehicle sends the current motion state information to its neighboring vehicles. If there is a communication channel connecting the starting vehicle to the destination vehicle, the destination vehicle is the neighbor of the starting vehicle, and the neighboring vehicle j∈Ω of vehicle i i ,Ω i is the set of neighbors of the i-th vehicle, if

[0022]

[0023] Then the neighboring car j uses the open loop system model The state transition matrix To predict the current state of the vehicle, λ>0 is an adjustable parameter used to adjust the distribution of sending time. Reducing the value of λ can reduce the communication time; increasing the value of λ can increase the communication time.

[0024] Furthermore, when the difference between the control signal at the current moment and the control signal at the previous sending moment is greater than a set threshold, the event-triggered communication module sends and executes the current control signal to adjust the throttle opening.

[0025] Furthermore, the event-triggered control module of the vehicle in step S5 constructs an adaptive control law using the state information received from the neighboring vehicle and the state information of the vehicle itself to suppress the state difference x between the neighboring vehicles. i (t)-x j (t)-d ij , then the adaptive dynamic coupling coefficient is calculated at each moment, and the control signal is designed through the system matrix A and the constant vector b to check whether the ego-vehicle control meets the triggering conditions.

[0026] Furthermore, the adaptive dynamic coupling coefficient formula is:

[0027]

[0028] Among them, d ij =[L ij 0 0] T , k ij It is an adjustable parameter used to control the growth rate of the coupling coefficient.

[0029] Furthermore, the control signal is designed by the system matrix A and the constant vector b, and the matrix Riccati equation is first solved:

[0030] PA+A T P-Pbb T P+I=0

[0031] A positive definite matrix P is obtained, where I is the identity matrix, and the control signal is expressed as:

[0032]

[0033] Among them, c ij (t) is the dynamic coupling coefficient of the controller, and the initial value c ij (0)≥0;

[0034] Check the current time t of vehicle i and the previous sending time The difference between the controller outputs Whether the norm of exceeds a time decay threshold; if not, no control signal is sent to the vehicle engine, and the engine throttle opening remains unchanged; otherwise, the engine executes u i (t), if

[0035]

[0036] but in, It is an adjustable parameter used to adjust the distribution and total number of sending times and reduce value, the number of actuator actions will decrease accordingly; if it increases value, the number of actuator actions increases accordingly.

[0037] Furthermore, the connected vehicle fleet refers to a passage consisting of multiple one-way channels at any time, pointing from the head vehicle i=1 to the tail vehicle i=N.

[0038] Furthermore, the triggering conditions in the event-triggered communication module and the event-triggered control module are of a decentralized structure, which is only related to the vehicle status information and has nothing to do with the neighboring vehicle information.

[0039] Furthermore, the adaptive control law is a distributed structure, that is, the control law is related to the state information of the own vehicle and the neighboring vehicles.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] 1. The present invention provides an event-triggered communication and control method for platooning. Compared with other similar technologies, the form of event trigger conditions and the structure of adaptive control law are more concise. The event trigger condition only needs to adjust the value of λ and change the distribution of sending time. Reducing the value of λ can reduce the communication time; increasing the value of λ can increase the communication time; the adaptive control law only needs to adjust value, reduce value, the number of actuator actions will decrease accordingly; if it increases value, the number of actuator actions increases accordingly. Both have only one adjustable parameter, which is convenient for agile design and beneficial for engineering implementation.

[0042] 2. The event triggering condition adopted by the present invention is a decentralized structure. The event triggering condition is only related to the vehicle status information and has nothing to do with the neighboring vehicle information. Poor exercise status Whether the norm of exceeds a dynamic threshold of time decay is used to determine whether to send status information, which effectively saves the network bandwidth of the Internet of Vehicles and the energy consumption of terminal devices, avoids the waste of spectrum resources caused by continuous communication, and is of great significance to improving spectrum utilization and reducing communication costs.

[0043] 3. The adaptive control law adopted in the present invention has a distributed structure and is only related to the state information of the vehicle and neighboring vehicles. By checking the current time t of vehicle i and the previous sending time The difference between the controller outputs Whether to send a control signal to the vehicle engine is determined by whether a time decay threshold is exceeded, and the controller gain can be automatically adjusted to adapt to various communication topologies with connectivity. This can increase the reliability of large-scale intelligent connected vehicle platooning and reduce the frequency of network induced phenomena caused by limited communication bandwidth. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 It is a schematic diagram of the process of the present invention;

[0045] Figure 2 This is an example diagram of the vehicle fleet communication topology of the present invention;

[0046] Figure 3 It is a schematic diagram of the displacement of each vehicle under the event triggering strategy of the present invention;

[0047] Figure 4 It is a schematic diagram of the speed of each vehicle under the event triggering strategy of the present invention;

[0048] Figure 5 It is a schematic diagram of the acceleration of each vehicle under the event triggering strategy of the present invention;

[0049] Figure 6 It is a schematic diagram of the communication time of each vehicle under the event triggering strategy of the present invention;

[0050] Figure 7 It is a schematic diagram of the execution time of each vehicle under the event triggering strategy of the present invention;

[0051] Figure 8 It is a schematic diagram of the speed of each vehicle under the periodic sending strategy of the present invention;

[0052] Fig. 9 It is a schematic diagram of the acceleration of each vehicle under the periodic sending strategy of the present invention. DETAILED DESCRIPTION

[0053] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0054] like Figure 1 As shown, an event-triggered communication and control method for platoon driving includes the following steps:

[0055] S1. Set up a connected fleet consisting of N vehicles, and install an event-triggered communication module and an event-triggered control module on each vehicle;

[0056] S2, the vehicle's event-triggered communication module checks whether the vehicle communication meets the triggering condition at a fixed sampling period, if so, execute step S3; if not, execute step S4;

[0057] S3, the vehicle sends status information to the neighboring vehicle;

[0058] S4, the neighboring vehicle uses the vehicle state information at the previous sending time to predict the vehicle state at the current time;

[0059] S5, the vehicle event trigger control module uses the state information to construct an adaptive control law, and checks whether the vehicle control meets the trigger condition at a fixed sampling period. If so, execute step S6; if not, execute step S7;

[0060] S6, the vehicle sends a new control signal to the engine and executes it;

[0061] S7. The control signal of the vehicle remains unchanged.

[0062] In step S2, the event-triggered communication module of the vehicle constructs the longitudinal dynamics model of the vehicle, sets the evolution model and motion state of the virtual navigator, and checks whether the self-vehicle communication meets the triggering conditions at a fixed sampling period.

[0063] The longitudinal dynamics model of the i-th vehicle in the event-triggered communication module is expressed as:

[0064]

[0065] Among them, x i (t) = [p i ,v i ,a i ] T is the state vector, p i is the position, v i is the speed, a i is the acceleration, u i (t) is the control signal, A is the system matrix, b is the vector, and Where τ>0 is the engine time constant;

[0066] Vehicle i (i = 1…N) controls input u i (t), the state x of vehicle i i (t) Following the state x of the virtual navigator 0 (t) changes, x 0 (t) In the lead vehicle i=1, according to the set initial condition x 0 (0) is calculated, and its evolution model is expressed as:

[0067]

[0068] Among them, x 0 (t) is the state of the virtual navigator, u 0 (t) is the control input of the virtual navigator, which is adjusted by u 0 (t) to control x 0 (t), the virtual navigator is the object to be tracked by all vehicles in the convoy. The goal of all vehicles is to keep the speed and acceleration consistent with the virtual navigator, and to keep a certain formation with the navigator;

[0069] For vehicle i in the fleet, check the current time t and its previous sending time Poor exercise status Whether the norm of exceeds a time-decayed dynamic threshold, if not, vehicle i does not send a signal to its neighbor vehicle j∈Ω at the current time t i Send status information x i (t); if it exceeds, the vehicle sends the current motion state information to its neighboring vehicles. If there is a communication channel connecting the starting vehicle to the destination vehicle, the destination vehicle is the neighbor of the starting vehicle, and the neighboring vehicle j∈Ω of vehicle i i ,Ω i is the set of neighbors of the i-th vehicle, if

[0070]

[0071] Then the neighboring car j uses the open loop system model The state transition matrix To predict the current state of the vehicle, λ>0 is an adjustable parameter used to adjust the distribution of sending time. Reducing the value of λ can reduce the communication time; increasing the value of λ can increase the communication time.

[0072] When the difference between the control signal at the current moment and the control signal at the previous sending moment is greater than a set threshold, the event-triggered communication module sends and executes the current control signal to adjust the throttle opening.

[0073] In step S5, the event-triggered control module of the vehicle constructs an adaptive control law using the state information received from the neighboring vehicle and the state information of the vehicle itself to suppress the state difference x between the neighboring vehicles. i (t)-x j (t)-d ij , then the adaptive dynamic coupling coefficient is calculated at each moment, and the control signal is designed through the system matrix A and the constant vector b to check whether the ego-vehicle control meets the triggering conditions.

[0074] The formula for the adaptive dynamic coupling coefficient is:

[0075]

[0076] Among them, d ij =[L ij 0 0] T , k ij It is an adjustable parameter used to control the growth rate of the coupling coefficient.

[0077] The control signal is designed by the system matrix A and the constant vector b. First, the matrix Riccati equation is solved:

[0078] PA+A TP-Pbb T P+I=0

[0079] A positive definite matrix P is obtained, where I is the identity matrix, and the control signal is expressed as:

[0080]

[0081] Among them, c ij (t) is the dynamic coupling coefficient of the controller, and the initial value c ij (0)≥0;

[0082] Check the current time t of vehicle i and the previous sending time The difference between the controller outputs Whether the norm of exceeds a time decay threshold; if not, no control signal is sent to the vehicle engine, and the engine throttle opening remains unchanged; otherwise, the engine executes u i (t), if

[0083]

[0084] but in, It is an adjustable parameter used to adjust the distribution and total number of sending times and reduce value, the number of actuator actions will decrease accordingly; if it increases value, the number of actuator actions increases accordingly.

[0085] A connected convoy means that at any time, there are multiple one-way channels, from the first car i=1 to the last car i=N.

[0086] The trigger conditions in the event-triggered communication module and the event-triggered control module are decentralized structures, which are only related to the vehicle status information and have nothing to do with the neighboring vehicle information.

[0087] The adaptive control law is a distributed structure, that is, the control law is related to the state information of the vehicle and neighboring vehicles.

[0088] use Figure 2 The convoy communication topology shown in Figure 2 is selected with τ = 0.5, N = 4, and x 1 =[20 2 0] T , x 2 =[150.5 0.6] T , x 3 =[8 0.3 0.3] T , x 4 =[2 0.5 0.2] T , L ij =7, c ij (0) = 2, k 21=0.1, k 32 =0.01, k 43 =0.01, λ=20, k=50, u 1 = -1;

[0089] Solving the matrix Riccati equation yields:

[0090]

[0091] The sampling period T is set to 0.05s, and the total number of times vehicles 1-3 send to the vehicles they follow is 33, 34, and 37 respectively. The number of executions of vehicles 2-4 is 76, 71, and 90 respectively. The traditional periodic sending strategy requires 200 data transmissions and 200 executions within 10s to complete the task of multi-vehicle state synchronization. Therefore, compared with the periodic sending strategy, this method can save more than 80% of the number of transmissions and more than 50% of the number of executions.

[0092] from Figure 3-Figure 9 It can be seen that the speed and acceleration curves of each vehicle under the periodic sending strategy are smoother than those under the event triggering strategy. The main reason is that when the event triggering condition is not met, the state information predicted by the vehicle to the neighboring vehicle is inaccurate. Although the control performance of the event triggering strategy is slightly reduced, the number of communications and executions is greatly reduced. If the number of communications and executions is increased, the state curve of the event triggering strategy will be closer and closer to the state curve of the periodic sending strategy. In practical applications, the total number of sending and execution can be changed by adjusting parameters according to the requirements of the actual system for control performance.

[0093] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. An event-triggered communication and control method for platooning, characterized in that: The following steps are involved: S1. Set up a connected fleet consisting of N vehicles, and install an event-triggered communication module and an event-triggered control module on each vehicle; S2, the vehicle's event-triggered communication module checks whether the vehicle communication meets the triggering condition at a fixed sampling period, if so, execute step S3; if not, execute step S4; S3, the vehicle sends status information to the neighboring vehicle; S4, the neighboring vehicle uses the vehicle state information at the previous sending time to predict the vehicle state at the current time; S5, the vehicle event trigger control module uses the state information to construct an adaptive control law, and checks whether the vehicle control meets the trigger condition at a fixed sampling period. If so, execute step S6; if not, execute step S7; S6, the vehicle sends a new control signal to the engine and executes it; S7, the control signal of the vehicle remains unchanged; In step S2, the vehicle's event-triggered communication module constructs a longitudinal dynamics model of the vehicle, sets an evolution model and motion state of the virtual navigator, and checks whether the vehicle communication meets the triggering conditions at a fixed sampling period; The longitudinal dynamics model of the ith vehicle in the event-triggered communication module is expressed as: Among them, x i (t) = [p i ,v i ,a i ] T is the state vector, p i is the position, v i is the speed, a i is the acceleration, u i (t) is the control signal, A is the system matrix, b is the vector, and Where τ>0 is the engine time constant; Vehicle i (i = 1…N) controls input u i (t), the state x of vehicle i i (t) follows the state x0(t) of the virtual navigator. x0(t) is calculated in the lead vehicle i=1 according to the set initial condition x0(0). Its evolution model is expressed as: Among them, x0(t) is the state of the virtual navigator, u0(t) is the control input of the virtual navigator, and x0(t) is controlled by adjusting u0(t). The virtual navigator is the object to be tracked by all vehicles in the convoy. The goal of all vehicles is to keep the speed and acceleration consistent with the virtual navigator, and to keep a certain formation with the navigator. For vehicle i in the fleet, check the current time t and its previous sending time Poor exercise status Whether the norm of exceeds a time-decayed dynamic threshold, if not, vehicle i does not send a signal to its neighbor vehicle j∈Ω at the current time t i Send status information x i (t); if it exceeds, the vehicle sends the current motion state information to its neighboring vehicles. If there is a communication channel connecting the starting vehicle to the destination vehicle, the destination vehicle is the neighbor of the starting vehicle, and the neighboring vehicle j∈Ω of vehicle i i ,Ω i is the set of neighbors of the i-th vehicle, if Then the neighboring car j uses the open loop system model The state transition matrix To predict the current state of the vehicle, λ>0 is an adjustable parameter used to adjust the distribution of sending time. Reducing the value of λ can reduce the communication time; increasing the value of λ can increase the communication time; In step S5, the event-triggered control module of the vehicle constructs an adaptive control law using the state information received from the neighboring vehicle and the state information of the vehicle itself to suppress the state difference x between the neighboring vehicles. i (t)-x j (t)-d ij , then the adaptive dynamic coupling coefficient is calculated at each moment, and the control signal is designed through the system matrix A and the constant vector b to check whether the ego-vehicle control meets the triggering conditions; The formula for the adaptive dynamic coupling coefficient is: Among them, d ij =[L ij 0 0] T , k ij is an adjustable parameter used to control the growth rate of the coupling coefficient; The control signal is designed by the system matrix A and the constant vector b, and the matrix Riccati equation is first solved: PA+A T P-Pbb T P+I=0 A positive definite matrix P is obtained, where I is the identity matrix, and the control signal is expressed as: Among them, c ij (t) is the dynamic coupling coefficient of the controller, and the initial value c ij (0)≥0; Check the current time t of vehicle i and the previous sending time The difference between the controller outputs Whether the norm of exceeds a time decay threshold; if not, no control signal is sent to the vehicle engine, and the engine throttle opening remains unchanged; otherwise, the engine executes u i (t), if but in, It is an adjustable parameter used to adjust the distribution and total number of sending times and reduce value, the number of actuator actions will decrease accordingly; if it increases value, the number of actuator actions increases accordingly.

2. The event-triggered communication and control method for platooning according to claim 1, characterized in that: When the difference between the control signal at the current moment and the control signal at the previous sending moment is greater than a set threshold, the event-triggered communication module sends and executes the current control signal to adjust the throttle opening.

3. The event-triggered communication and control method for platooning according to claim 1, characterized in that: The connected vehicle fleet refers to a passage consisting of multiple one-way channels at any time, pointing from the head vehicle i=1 to the tail vehicle i=N.

4. The event-triggered communication and control method for platooning according to claim 1, characterized in that: The triggering conditions in the event-triggered communication module and the event-triggered control module are decentralized structures, which are only related to the vehicle status information and have nothing to do with the neighboring vehicle information.

5. The event-triggered communication and control method for platooning according to claim 1, characterized in that: The adaptive control law is a distributed structure, that is, the control law is related to the state information of the own vehicle and the neighboring vehicles.

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