Cooperative vehicle infrastructure time synchronization method, cooperative vehicle infrastructure time synchronization device and system

Abstract

A vehicle-road cooperation time synchronization method, a vehicle-road cooperation time synchronization device and a system belong to the field of time synchronization. The vehicle-road cooperation time synchronization method comprises: judging whether a vehicle-mounted NTP server (20) receives a first GPS time signal (S100); when the vehicle-mounted NTP server (20) does not receive the first GPS time signal, simultaneously reading NTP hierarchical information of a vehicle-road cooperation NTP server (70) and NTP (50) hierarchical information of a first remote time server, and synchronizing the vehicle-mounted NTP server (20) with the one with lower level among the two (S200); after synchronization is successful, sending a first synchronization instruction to each vehicle-mounted sensor data processing unit (80) to make each vehicle-mounted sensor data processing unit (80) synchronize the time of the vehicle-mounted NTP server (20) through a network time protocol (S300). The vehicle-road cooperation time synchronization method, the synchronization device and the system can meet the requirements of automatic driving.

Description

Technical Field

[0001] This invention relates to the field of time synchronization, and in particular to a vehicle-road cooperative time synchronization method, a vehicle-road cooperative time synchronization device and system. Background Technology

[0002] Currently, in the system framework of vehicle-road cooperative driving, the onboard perception system and the roadside perception system are relatively independent, making it very difficult to fully utilize the perception information from both to achieve more comprehensive and accurate perception. At present, the traditional approach is to use the onboard perception system as the primary system and the roadside perception system as a supplement. In low-level autonomous driving functions, the information provided by the roadside perception system is only used to remind and warn the driver; in high-level autonomous driving functions, the perception information actually involved in decision-making and control is still provided by the onboard perception system, with the roadside perception system only providing traffic light information at intersections for decision-making and planning. The proportion and weight of the perception information provided by the roadside perception system in decision-making are very low. Several factors contribute to this: 1. The types and quantities of sensors used in current roadside perception systems are limited, and the perception range cannot fully cover intersections; 2. Roadside perception cannot be fused with onboard perception data because the roadside perception system is not time-synchronized with the onboard perception system. Consider a common scenario where the onboard perception system and the roadside perception system are independent, each with its own clock source, and the offset between the vehicle's time source and the roadside time source is unknown. For the same target, the onboard sensors... The latency of constantly sensing the target, processing it through algorithms, and transmitting it. The data is then transmitted to the perception fusion module; simultaneously, the roadside sensors... The latency of constantly sensing the same target, processing it through algorithms, and transmitting it. The data is then transmitted to the perception fusion module. The fusion module cannot fuse these two frames of target information for the following reasons: 1. The perception fusion module cannot determine the actual sequence of events between the two frames; 2. The perception fusion module cannot determine the actual time difference between the two frames. Therefore, the actual effect is that for the same object, there will be multiple ghost images, meaning a single object is perceived as multiple objects.

[0003] Traditional autonomous driving time synchronization solutions only consider the onboard sensor system. They select a master clock from multiple onboard CPU computing units, with other sensors acting as slave clocks, synchronizing with the master clock via the vehicle's local area network (LAN). There are no specific requirements for the selection of the master clock. This is feasible for single-vehicle intelligence because the inboard LAN structure is simple, and communication between sensors and the CPU does not require routing, resulting in low and stable transmission latency. However, within the framework of vehicle-to-infrastructure (V2I) communication, this solution is insufficient because it cannot incorporate roadside sensors into the time synchronization system. This is because the communication link between roadside sensors and the onboard CPU is complex and variable, and its wireless transmission is unstable. If the same method is used to synchronize the clocks of roadside sensors, the synchronization effect between roadside sensors and the onboard CPU cannot be as good as that between onboard sensors and the onboard CPU due to network environment limitations, thus failing to meet the requirements of autonomous driving. Summary of the Invention

[0004] In view of the above problems, the present invention is proposed to provide a vehicle-road cooperative time synchronization method, vehicle-road cooperative time synchronization device and system to overcome the above problems or at least partially solve the above problems.

[0005] One objective of the first aspect of this invention is to provide a vehicle-road cooperative time synchronization method for vehicles applied to a vehicle-road cooperative system, which can meet the requirements of autonomous driving.

[0006] Another objective of this invention is to achieve time synchronization between vehicles and roadside equipment, controlling the actual error to the microsecond level.

[0007] A second aspect of the present invention aims to provide a vehicle-road cooperative time synchronization method for roadside equipment applied to a vehicle-road cooperative system, which can meet the requirements of autonomous driving.

[0008] A third aspect of the present invention aims to provide a vehicle-road cooperative time synchronization device for use in a vehicle-road cooperative system, which can meet the requirements of autonomous driving.

[0009] A fourth aspect of the present invention aims to provide a vehicle-road cooperative time synchronization device for roadside equipment in a vehicle-road cooperative system, which can meet the requirements of autonomous driving.

[0010] One objective of the fifth aspect of this invention is to provide a vehicle-road cooperative time synchronization system to solve the fundamental problems currently hindering vehicle-road cooperative perception fusion, and to lay a solid foundation for promoting vehicle-road cooperative perception fusion.

[0011] In particular, according to a first aspect of the present invention, a vehicle-road cooperative time synchronization method is provided, applied to a vehicle in a vehicle-road cooperative system. The vehicle includes an onboard GPS timing unit, an onboard NTP server, and multiple onboard sensor data processing units. The onboard NTP server is connected to the onboard GPS timing unit and a first remote time server, respectively. The onboard GPS timing unit is configured to provide a first GPS timing signal to the onboard NTP server when a GPS signal is normally acquired. The vehicle-road cooperative system also includes roadside equipment, which includes a vehicle-road cooperative NTP server. The vehicle-road cooperative time synchronization method includes: Determine whether the vehicle-mounted NTP server has received the first GPS timing signal; When the vehicle-mounted NTP server does not receive the first GPS timing signal, it simultaneously reads the NTP level information of the vehicle-road cooperative NTP server and the NTP level information of the first remote time server, and synchronizes the vehicle-mounted NTP server with the one with the lower level. After successful synchronization, a first synchronization command is sent to each of the vehicle-mounted sensor data processing units so that each of the vehicle-mounted sensor data processing units synchronizes the time of the vehicle-mounted NTP server via Network Time Protocol.

[0012] Optionally, after determining whether the vehicle-mounted NTP server has received the first GPS timing signal, the method further includes: When the vehicle-mounted NTP server receives the first GPS timing signal, it synchronizes the GPS hardware reference time.

[0013] Optionally, the vehicle-mounted GPS timing unit includes a connected integrated inertial navigation system and a signal expansion board. The signal expansion board is connected to the vehicle-mounted NTP server. The vehicle also includes a vehicle-mounted lidar connected to the signal expansion board to obtain the first GPS timing signal through the signal expansion board. The vehicle-road cooperative time synchronization method also includes: Determine whether the vehicle-mounted lidar has received the first GPS timing signal; When the vehicle-mounted lidar receives the first GPS timing signal, it synchronizes the vehicle-mounted lidar with the GPS hardware reference time.

[0014] Optionally, after determining whether the vehicle-mounted lidar has received the first GPS timing signal, the method further includes: When the vehicle-mounted lidar does not receive the first GPS timing signal, the vehicle-mounted lidar synchronizes with the time of the onboard NTP server.

[0015] Optionally, the step of synchronizing the vehicle-mounted LiDAR with the time of the onboard NTP server when the vehicle-mounted LiDAR does not receive the first GPS timing signal includes: The transmission latency of the test node in the local area network where the vehicle-mounted lidar is located is detected when communicating with the vehicle-mounted NTP server. The test node is connected to the vehicle-mounted NTP server through a switch. The local time of the vehicle-mounted LiDAR is determined based on the transmission delay and the local time of the vehicle-mounted NTP server.

[0016] Optionally, the step of detecting the transmission delay when the test node in the local area network where the vehicle-mounted LiDAR is located communicates with the vehicle-mounted NTP server includes: The vehicle-mounted NTP server transmits a first data packet carrying the first transmission time to the test node at the first transmission time, records the first reception time of the test node receiving the first data packet, and calculates the difference A2B between the first reception time and the first transmission time. The test node transmits a second data packet carrying the second transmission time to the vehicle-mounted NTP server at the second transmission time, records the second reception time of the vehicle-mounted NTP server receiving the second data packet, and calculates the difference B2A between the second reception time and the second transmission time. The clock offset C is calculated according to the following formula (1): C = (A2B - B2A) / 2 (1); The transmission delay ΔT^' is calculated according to the following formula (2): ΔT^'=A2B –C (2).

[0017] Optionally, the step of determining the local time of the vehicle-mounted LiDAR based on the transmission delay and the local time of the vehicle-mounted NTP server includes: The vehicle-mounted NTP server sends a second synchronization command to the vehicle-mounted lidar at a third moment, and the second synchronization command carries the transmission delay. When the vehicle-mounted lidar receives the second synchronization command, the local time of the vehicle-mounted lidar is set to the sum of the third time point and the transmission delay.

[0018] Optionally, the vehicle-road cooperative NTP server is timed by a roadside GPS timing unit or a second remote time server; When the vehicle-road cooperative NTP server is synchronized with the roadside GPS timing unit, the NTP level of the vehicle-road cooperative NTP server is lower than the NTP level of the first remote time server. The steps to synchronize the onboard NTP server with the lower-level of the two include: When the vehicle-road cooperative NTP server is timed by the roadside GPS timing unit, the vehicle-mounted NTP server is synchronized with the vehicle-road cooperative NTP server.

[0019] In particular, according to a second aspect of the present invention, a vehicle-road cooperative time synchronization method is provided, applied to roadside equipment in a vehicle-road cooperative system. The roadside equipment includes a roadside GPS timing unit, a vehicle-road cooperative NTP server, and multiple roadside sensor data processing units. Each roadside sensor data processing unit is connected to the vehicle-road cooperative NTP server. The vehicle-road cooperative NTP server receives a second GPS timing signal from the roadside GPS timing unit or receives timing from a second remote time server. The vehicle-road cooperative system further includes a vehicle, which includes an onboard GPS timing unit and an onboard NTP server connected to both the onboard GPS timing unit and a first remote time server. The onboard GPS timing unit is configured to provide a first GPS timing signal to the onboard NTP server when a GPS signal is normally acquired. The onboard NTP server is connected to the vehicle-road cooperative NTP server. The vehicle-road cooperative time synchronization method includes: The vehicle-road cooperative time synchronization method includes: Determine whether the vehicle-road cooperative NTP server has received the second GPS timing signal; When the vehicle-road cooperative NTP server receives the second GPS timing signal, the vehicle-road cooperative NTP server synchronizes the GPS hardware reference time. The system receives a synchronization request sent by the vehicle-mounted NTP server and responds to the synchronization request by providing a reference time to the vehicle-mounted NTP server for synchronization. The synchronization request is sent by the vehicle-mounted NTP server when it has not received the first GPS timing signal and the NTP level of the vehicle-road cooperative NTP server is lower than the NTP level of the first remote time server. A third synchronization command is sent to each of the roadside sensor data processing units so that each of the roadside sensor data processing units synchronizes the time of the vehicle-road cooperative NTP server via Network Time Protocol.

[0020] Optionally, when the vehicle-road cooperative NTP server is timed by the roadside GPS timing unit, the NTP level of the vehicle-road cooperative NTP server is lower than the NTP level of the first remote time server.

[0021] Optionally, after determining whether the vehicle-to-infrastructure (V2I) cooperative NTP server has received the second GPS timing signal, the method further includes: When the vehicle-road cooperative NTP server does not receive the second GPS timing signal, the vehicle-road cooperative NTP server synchronizes its time with the second remote time server.

[0022] In particular, according to a third aspect of the present invention, a first vehicle-road cooperative time synchronization device is provided, applied to a vehicle in a vehicle-road cooperative system. The first vehicle-road cooperative time synchronization device includes an on-board GPS timing unit, an on-board NTP server, a plurality of on-board sensor data processing units, a memory, and a processor. The on-board NTP server is connected to the on-board GPS timing unit and a first remote time server, respectively. The memory stores a control program, which, when executed by the processor, is used to implement the vehicle-road cooperative time synchronization method for a vehicle applied to a vehicle-road cooperative system according to any of the above-described embodiments.

[0023] In particular, according to a fourth aspect of the present invention, a second vehicle-road cooperative time synchronization device is provided, applied to roadside equipment in a vehicle-road cooperative system. The second vehicle-road cooperative time synchronization device includes a roadside GPS timing unit, a vehicle-road cooperative NTP server, multiple roadside sensor data processing units, a memory, and a processor. Each of the roadside sensor data processing units is connected to the vehicle-road cooperative NTP server. The vehicle-road cooperative NTP server is provided with a second GPS timing signal by the roadside GPS timing unit or with timing signal from a second remote time server. The memory stores a control program, which, when executed by the processor, is used to implement a vehicle-road cooperative time synchronization method for roadside equipment applied to a vehicle-road cooperative system.

[0024] In particular, according to a fifth aspect of the present invention, a vehicle-road cooperative time synchronization system is provided, including a first vehicle-road cooperative time synchronization device and a second vehicle-road cooperative time synchronization device.

[0025] In the vehicle-to-infrastructure (V2I) time synchronization method of the present invention, when the onboard NTP server receives the first GPS timing signal, it synchronizes with the GPS hardware reference time to obtain accurate UTC time. If the onboard NTP server does not receive the first GPS timing signal, it can obtain a relatively accurate time by obtaining time from the lower-level V2I NTP server or the first remote time server, ensuring that the local time error of the onboard NTP server does not accumulate over time. In particular, even when the onboard NTP server cannot obtain the first GPS timing signal, it can still obtain accurate time from the V2I NTP server that can obtain the second GPS timing signal. This allows the time error between the entire vehicle-side autonomous driving system and UTC time to be controlled at the microsecond level, meeting the requirements of V2I autonomous driving.

[0026] Furthermore, in the method of the present invention, the GPS timing signal (UTC time and PPS signal) is extended by combining an inertial navigation system and a signal extension board and provided to each lidar and vehicle-mounted NTP server, so that each lidar and vehicle-mounted NTP server can obtain an accurate GPS timing signal.

[0027] Furthermore, in the method of the present invention, when the vehicle-mounted LiDAR cannot receive an accurate and reliable hardware reference time, and it supports the method of configuring the local time by sending instructions via the Ethernet port, the local time of the vehicle-mounted LiDAR is determined by testing the transmission delay and then based on the transmission delay and the local time of the vehicle-mounted NTP server, so as to maintain the error between the vehicle-mounted LiDAR and the time source.

[0028] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and in order to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below.

[0029] The above and other objects, advantages and features of the present invention will become more apparent to those skilled in the art from the following detailed description of specific embodiments of the invention in conjunction with the accompanying drawings. Attached Figure Description

[0030] The following sections will describe some specific embodiments of the invention in detail by way of example and not limitation, with reference to the accompanying drawings. The same reference numerals in the drawings denote the same or similar parts or portions. Those skilled in the art should understand that these drawings are not necessarily drawn to scale. In the drawings: Figure 1 This is a flowchart of a vehicle-road cooperative time synchronization method for vehicles applied to a vehicle-road cooperative system according to an embodiment of the present invention; Figure 2 This is a connection block diagram of a vehicle applied to a vehicle-road cooperative system according to an embodiment of the present invention; Figure 3 This is a flowchart of a vehicle-road cooperative time synchronization method for vehicles applied to a vehicle-road cooperative system according to another embodiment of the present invention; Figure 4 This is a flowchart of a vehicle-road cooperative time synchronization method for roadside equipment applied to a vehicle-road cooperative system according to an embodiment of the present invention; Figure 5 This is a connection block diagram of a roadside device applied to a vehicle-road cooperative system according to an embodiment of the present invention; Figure 6 This is a diagram illustrating the NTP time synchronization principle between the client and the server. Figure 7This is a connection block diagram of a vehicle-road cooperative time synchronization system according to an embodiment of the present invention. Detailed Implementation

[0031] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0032] Figure 1 This is a flowchart of a vehicle-road cooperative time synchronization method for vehicles applied to a vehicle-road cooperative system according to an embodiment of the present invention. Figure 2 This is a connection block diagram of a vehicle applied to a vehicle-road cooperative system according to an embodiment of the present invention. The vehicle-road cooperative time synchronization method of this embodiment is applied to vehicles in the vehicle-road cooperative system, which includes vehicles and roadside equipment. Figure 2 As shown, the vehicle includes an onboard GPS timing unit 10, an onboard NTP server 20, and multiple onboard sensor data processing units 30. The onboard NTP server 20 is connected to both the onboard GPS timing unit 10 and a first remote time server 50. The onboard GPS timing unit 10 is configured to provide a first GPS timing signal to the onboard NTP server 20 when a GPS signal is normally acquired. The lengths of the wires transmitting the first GPS timing signal should be as short and uniform as possible to ensure that the time delay caused by wire transmission is minimized and consistent, thereby ensuring the accuracy of the first GPS timing signal. This is easily achieved at the vehicle end. The onboard GPS timing unit 10 can provide a pulse-second signal (PPS) and a UTC time synchronization signal. The time in the UTC time synchronization signal corresponds to the rising edge of the PPS signal. The onboard NTP server 20 is a device in the vehicle deployed with NTP service, capable of updating its own time to UTC time at the rising edge of the PPS signal. Optionally, the onboard sensor data processing unit 30 includes a general-purpose processing unit 31 corresponding to millimeter-wave radar, ultrasonic radar, and chassis sensors, as well as a dedicated processing unit 32 corresponding to the camera. The roadside equipment includes a vehicle-to-infrastructure (V2I) cooperative NTP server 70. The V2I cooperative NTP server 70 is synchronized with the roadside GPS timing unit 60 or a second remote time server 90. When the roadside GPS timing unit 60 obtains a normal GPS signal, it provides a second GPS timing signal to the V2I cooperative NTP server 70.

[0033] like Figure 1 As shown, the vehicle-road cooperative time synchronization method in this embodiment includes: Step S100: Determine whether the vehicle-mounted NTP server 20 has received the first GPS timing signal. If not, proceed to step S200.

[0034] In step S200, the NTP level information of the vehicle-to-infrastructure (V2I) cooperative NTP server 70 and the NTP level information of the first remote time server 50 are read simultaneously, and the vehicle-mounted NTP server 20 is synchronized with the one with the lower level. When the V2I cooperative NTP server 70 is synchronized by the roadside GPS timing unit 60, the NTP level of the V2I cooperative NTP server 70 is lower than that of the first remote time server 50. In this case, the vehicle-mounted NTP server 20 is synchronized with the V2I cooperative NTP server 70. When the V2I cooperative NTP server 70 is synchronized by the second remote time server 90, the synchronization target of the vehicle-mounted NTP server 20 still needs to be determined according to the NTP level of the first remote time server 50 and the V2I cooperative NTP server 70. Since the levels of the first remote time server 50 and the second remote time server 90 are determined by their distance from the GPS time node, the farther away from the GPS node, the higher the level. Therefore, based on the hierarchical information of the first remote time server 50 and the second remote time server 90 determined in the actual situation, the NTP level of the first remote time server 50 and the vehicle-road cooperative NTP server 70 can be determined. For example, if the NTP level of the first remote time server 50 is 3 and the NTP level of the second remote time server 90 is 3, then the NTP level of the vehicle-road cooperative NTP server 70, which is timed by the second remote time server 90, is 4. At this time, the vehicle-mounted NTP server 20 selects the first remote time server 50 with the lower NTP level for time synchronization.

[0035] In step S300, after successful synchronization, a first synchronization command is sent to each vehicle sensor data processing unit 30 so that each vehicle sensor data processing unit 30 synchronizes the time of the vehicle NTP server 20 via the Network Time Protocol.

[0036] When an autonomous vehicle is driving in an area where satellite signals cannot be received, such as a tunnel, the onboard GPS timing unit 10 cannot obtain GPS signals normally. Consequently, the onboard NTP server 20 cannot obtain accurate and reliable UTC time by receiving the first GPS timing signal. The error between the local time and UTC time of the onboard NTP server 20 increases as the time the onboard GPS timing unit 10 cannot obtain GPS signals normally increases. In this embodiment, the onboard NTP server 20 can access the roadside vehicle-to-infrastructure (V2I) cooperative NTP server 70, and it can also connect to the first remote time server 50. Therefore, it can obtain time from both the V2I cooperative NTP server 70 and the first remote time server 50, selecting the lower-level (i.e., more accurate) server to synchronize the time. Generally, the vehicle-to-infrastructure (V2I) NTP server 70 can provide a second GPS timing signal through the roadside GPS timing unit 60. When the vehicle-mounted NTP server 20 cannot receive the first GPS timing signal through the vehicle's onboard GPS timing unit 10, the V2I NTP server 70 can still provide accurate time. In this case, the NTP level of the V2I NTP server 70 is 1, the NTP level of the vehicle-mounted NTP server 20 is 2, and the NTP level of the vehicle-mounted sensor data processing unit 30 is 3. Of course, the V2I NTP server 70 may also fail to provide accurate time due to signal interruption, equipment failure, etc. In this case, the vehicle-mounted NTP server 20 can also synchronize time through the first remote time server 50. Therefore, in this embodiment, when the vehicle-mounted NTP server 20 does not receive the first GPS timing signal, it can obtain a more accurate time by obtaining time from the lower-level vehicle-to-infrastructure (V2I) NTP server 70 or the first remote time server 50, ensuring that the local time error of the vehicle-mounted NTP server 20 does not accumulate over time. In particular, even when the on-board NTP server 20 cannot obtain the first GPS timing signal, it can still obtain the accurate time from the vehicle-road cooperative NTP server 70, which is able to obtain the second GPS timing signal. This allows the error between the time of the entire vehicle-side autonomous driving system and the UTC time to be controlled at the microsecond level, thus meeting the requirements of vehicle-road cooperative autonomous driving.

[0037] Of course, when the vehicle-mounted NTP server 20 cannot obtain an accurate time signal (i.e., the vehicle-mounted NTP server 20 cannot obtain the first GPS timing signal from the vehicle-mounted GPS timing unit 10, and the vehicle-road cooperative NTP server 70 does not obtain the second GPS timing signal), the vehicle-mounted NTP server 20 can only synchronize time from the first remote time server 50 or from the vehicle-road cooperative NTP server 70 (at this time, the vehicle-road cooperative NTP server 70 synchronizes time from the second remote time server 90). Although the time error of the vehicle-mounted NTP server 20 can be maintained, the error level inevitably decreases from the microsecond level to the millisecond level. In this case, the false detection introduced by vehicle-road cooperative perception fusion increases significantly, so the autonomous driving mode switches from vehicle-road cooperative to single-vehicle intelligence.

[0038] In one embodiment, such as Figure 1 As shown, after step S100, the following steps are also included: In step S400, when the vehicle-mounted NTP server 20 receives the first GPS timing signal, it synchronizes the GPS hardware reference time. Therefore, the vehicle-mounted NTP server 20 preferentially synchronizes time from the vehicle's onboard GPS timing unit 10 to obtain accurate UTC time.

[0039] Figure 3 This is a flowchart of a vehicle-to-infrastructure (V2I) time synchronization method for vehicles applied to a V2I system according to another embodiment of the present invention. In another embodiment, such as... Figure 2 As shown, the vehicle-mounted GPS timing unit 10 includes a connected integrated inertial navigation system 11 and a signal extension board 12. The integrated inertial navigation system 11 can be a vehicle-mounted integrated inertial navigation system 11 with a built-in GPS receiver module. The signal extension board 12 is connected to the vehicle-mounted NTP server 20. The vehicle also includes a vehicle-mounted LiDAR 40 connected to the signal extension board 12 to obtain the first GPS timing signal through the signal extension board 12.

[0040] like Figure 3 As shown, in this embodiment, the vehicle-road cooperative time synchronization method further includes: Step S500: Determine whether the vehicle-mounted LiDAR 40 has received the first GPS timing signal. If yes, proceed to step S600; otherwise, proceed to step S700.

[0041] Step S600: Synchronize the vehicle-mounted LiDAR 40 with the GPS hardware reference time.

[0042] Step S700: Synchronize the time of the vehicle-mounted LiDAR 40 with that of the vehicle-mounted NTP server 20.

[0043] Most LiDARs manufactured by mainstream LiDAR manufacturers now come with a built-in GPS timing interface, which can receive hardware reference time to achieve time synchronization. In this embodiment, the combined inertial navigation system 11 extends the GPS timing signal (UTC time and PPS signal) through the signal extension board 12 and provides it to each LiDAR and the vehicle-mounted NTP server 20, so that each LiDAR and the vehicle-mounted NTP server 20 can obtain accurate GPS timing signals.

[0044] In a further embodiment, such as Figure 3 As shown, step S700 includes: Step S701: Detect the transmission latency when the test node in the local area network where the vehicle-mounted LiDAR 40 is located communicates with the vehicle-mounted NTP server 20. The test node is connected to the vehicle-mounted NTP server 20 through a switch.

[0045] Step S702: Determine the local time of the vehicle-mounted LiDAR 40 based on the transmission delay and the local time of the vehicle-mounted NTP server 20.

[0046] Furthermore, step S701 includes: The vehicle-mounted NTP server 20 transmits a first data packet carrying the first transmission time to the test node at the first transmission time, records the first reception time of the test node receiving the first data packet, and calculates the difference A2B between the first reception time and the first transmission time. The test node transmits a second data packet carrying the second transmission time to the vehicle-mounted NTP server 20 at the second transmission time, records the second reception time of the vehicle-mounted NTP server 20 receiving the second data packet, and calculates the difference B2A between the second reception time and the second transmission time. The clock offset C is calculated according to the following formula (1): C = (A2B - B2A) / 2 (1) The transmission delay is calculated according to the following formula (2). : A2B –C (2) Step S702 includes: sending a second synchronization command from the vehicle-mounted NTP server 20 to the vehicle-mounted LiDAR at a third time, the second synchronization command carrying a transmission delay; and setting the local time of the vehicle-mounted LiDAR to the sum of the third time and the transmission delay when the vehicle-mounted LiDAR receives the second synchronization command. (3) in, For the local time of the vehicle-mounted LiDAR, This is the third moment.

[0047] Assuming the vehicle-mounted communication network structure remains unchanged, the transmission delay of the vehicle-mounted LiDAR can be considered the same as that of the test node. Therefore, in this embodiment, the calculated transmission delay of the test node is used as the transmission delay of the vehicle-mounted LiDAR. Since the transmission protocol of the vehicle-mounted LiDAR differs from that of the in-vehicle network, it is impossible to directly synchronize the time of the in-vehicle NTP server 20 via the NTP protocol. In this embodiment, when the vehicle-mounted LiDAR cannot receive an accurate and reliable hardware reference time, and it supports configuring its local time via Ethernet port commands, the above method is used to maintain the error between the vehicle-mounted LiDAR and the time source. The simple command transmission time within the in-vehicle local area network is generally at the microsecond level. The above method can control the error between the local time and UTC time of the vehicle-mounted LiDAR within microseconds when satellite signals are missing.

[0048] Figure 4 This is a flowchart of a vehicle-road cooperative time synchronization method for roadside equipment applied to a vehicle-road cooperative system according to an embodiment of the present invention. Figure 5 This is a connection block diagram of a roadside device applied to a vehicle-road cooperative system according to an embodiment of the present invention. In one embodiment, as shown... Figure 5 As shown, the roadside equipment includes a roadside GPS timing unit 60, a vehicle-to-infrastructure (V2I) cooperative NTP server 70, and multiple roadside sensor data processing units 80. Each roadside sensor data processing unit 80 is connected to the V2I cooperative NTP server 70. The V2I cooperative NTP server 70 receives a second GPS timing signal from the roadside GPS timing unit 60 or receives timing from a second remote time server 90. Optionally, the multiple roadside sensor data processing units 80 include general-purpose processing units 81 corresponding to multiple cameras and millimeter-wave radars deployed on the roadside, and dedicated processing units 82 corresponding to multiple lidars deployed on the roadside. The V2I cooperative system also includes a vehicle, which includes an onboard GPS timing unit 10 and an onboard NTP server 20. The onboard GPS timing unit 10 is configured to provide a first GPS timing signal to the onboard NTP server 20 when a GPS signal is normally acquired. The onboard NTP server 20 is connected to the V2I cooperative NTP server 70.

[0049] like Figure 4 As shown, in this embodiment, the vehicle-road cooperative time synchronization method applied to roadside equipment in the vehicle-road cooperative system includes: Step S110: Determine whether the vehicle-to-infrastructure (V2I) NTP server 70 has received the second GPS timing signal. If yes, proceed to step S120; otherwise, proceed to step S130.

[0050] Step S120: Synchronize the vehicle-to-infrastructure (V2I) NTP server 70 with the GPS hardware reference time. Then proceed to step S140.

[0051] Step S130: The vehicle-road cooperative NTP server 70 synchronizes its time with the second remote time server 90.

[0052] Step S140: Receive a synchronization request from the vehicle-mounted NTP server 20 and respond to the synchronization request by providing a reference time for synchronization. The synchronization request is issued by the vehicle-mounted NTP server 20 when it has not received the first GPS timing signal and the NTP level of the vehicle-to-infrastructure (V2I) cooperative NTP server 70 is lower than the NTP level of the first remote time server 50. When the V2I cooperative NTP server 70 is synchronized by the roadside GPS timing unit 60, the NTP level of the V2I cooperative NTP server 70 is lower than the NTP level of the first remote time server 50. When the V2I cooperative NTP server 70 is synchronized by the second remote time server 90, the NTP level of the first remote time server 50 and the V2I cooperative NTP server 70 needs to be determined based on the NTP level of the second remote time server 90. The specific determination of the NTP level has been detailed in step S200 above and will not be repeated here.

[0053] In step S150, a third synchronization command is sent to each roadside sensor data processing unit 80 so that each roadside sensor data processing unit 80 synchronizes its time with the vehicle-to-infrastructure (NTP) server 70 via Network Time Protocol (NTP). The execution order of steps S140 and S150 is not important.

[0054] In this embodiment, the vehicle-to-infrastructure (V2I) cooperative NTP server 70 preferentially obtains time through the roadside GPS timing unit 60. When time cannot be obtained through the roadside GPS timing unit 60, it obtains time through the second remote time server 90. Since the roadside GPS timing unit 60 is usually located in an open area, it is highly likely to obtain accurate satellite time synchronization, ensuring high time accuracy in the V2I cooperative NTP server 70. Furthermore, the V2I cooperative NTP server 70, which obtains time through the roadside GPS timing unit 60, can also provide time to the onboard NTP server 20, which cannot obtain time synchronization through the onboard GPS timing unit 10. This ensures that both the vehicle and the roadside obtain accurate time, guaranteeing precise synchronization of clocks between the vehicle and the roadside to meet the requirements of autonomous driving.

[0055] It should be noted that since the test nodes of the vehicle-mounted LiDAR can be freely set in the Ethernet, the time can be configured via Ethernet (steps S701 and S702). However, the LiDAR in the roadside equipment is usually provided by a third party, so the test nodes cannot be freely set. It is necessary to set up a dedicated data processor for the LiDAR to synchronize with the vehicle-road cooperative NTP server 70.

[0056] Figure 6This is a diagram illustrating the NTP time synchronization principle between the client and server. (Example) Figure 6 As shown, the client first sends an NTP message to the server, which includes the timestamp T1 of the message leaving the client. When the server receives the message, it sequentially fills in the timestamps T2 (arrival) and T3 (departure), and then immediately returns the message to the client. Upon receiving the response message, the client records the timestamp T4 of the returned message. Using these four time parameters, the client can calculate two key parameters: the round-trip time d of the NTP message and the clock skew t between the client and the server. The client uses the clock skew to adjust its local clock to match the server's time.

[0057] Given the values ​​T1, T2, T3, and T4, we want to determine t to adjust the customer's clock: (4) Assuming the NTP request and reply message transmission delays are equal, i.e., d1=d2, substituting into equation (4) yields the following solution: (5) According to equation (4), t can also be expressed as t=(T2-T1)+d1=(T2-T1)+d⁄2 (6) It can be seen that t and d are only related to the differences between T2 and T1 and the differences between T3 and T4, but not to the difference between T2 and T3. That is, the final result is independent of the time required for the server to process the request. Therefore, the client can calculate the time difference t using T1, T2, T3, and T4 to adjust its local clock.

[0058] Based on the above principle, time synchronization between any two devices that need to be synchronized in this invention can be achieved.

[0059] like Figure 2As shown, the first vehicle-to-infrastructure (V2I) cooperative time synchronization device 100 for vehicles in this embodiment, applied to a vehicle-to-infrastructure (V2I) cooperative system, includes an onboard GPS timing unit 10, an onboard NTP server 20, multiple onboard sensor data processing units 30, a memory, and a processor. The onboard NTP server 20 is connected to both the onboard GPS timing unit 10 and a first remote time server 50. Further, the onboard GPS timing unit 10 includes a connected integrated inertial navigation system 11 and a signal expansion board 12, with the signal expansion board 12 connected to the onboard NTP server 20. The first V2I cooperative time synchronization device 100 also includes a vehicle-end lidar 40 connected to the signal expansion board 12. The memory stores a control program, which, when executed by the processor, is used to implement the aforementioned V2I cooperative time synchronization method for vehicles in a V2I cooperative system. The processor can be a central processing unit (CPU) or a digital processing unit, etc. The processor sends and receives data via a communication interface. The memory stores the program executed by the processor. Memory is any medium capable of carrying or storing desired program code in the form of instructions or data structures, and accessible by a computer; it can also be a combination of multiple memories. The aforementioned computational program can be downloaded from a computer-readable storage medium to a corresponding computing / processing device or via a network (e.g., the Internet, local area network, wide area network, and / or wireless network) to a computer or external storage device.

[0060] like Figure 5 As shown, the second vehicle-road cooperative time synchronization device 200 for roadside equipment in this embodiment, applied to a vehicle-road cooperative system, includes a roadside GPS timing unit 60, a vehicle-road cooperative NTP server 70, multiple roadside sensor data processing units 80, a memory, and a processor. Each roadside sensor data processing unit 80 is connected to the vehicle-road cooperative NTP server 70. The vehicle-road cooperative NTP server 70 receives a second GPS timing signal from the roadside GPS timing unit 60 or is timed by a second remote time server 90. The memory stores a control program, which, when executed by the processor, is used to implement the vehicle-road cooperative time synchronization method for roadside equipment as described in any of the preceding embodiments or combinations thereof. The processor can be a central processing unit (CPU), a digital processing unit, etc. The processor sends and receives data through a communication interface. The memory stores the program executed by the processor. The memory is any medium capable of carrying or storing desired program code in the form of instructions or data structures and accessible by a computer; it can also be a combination of multiple memories. The aforementioned calculation program can be downloaded from a computer-readable storage medium to the corresponding computing / processing device or via a network (e.g., the Internet, local area network, wide area network, and / or wireless network) to a computer or external storage device.

[0061] Figure 7 This is a connection block diagram of a vehicle-road cooperative time synchronization system 300 according to an embodiment of the present invention. Figure 7 As shown, in this embodiment, the vehicle-road cooperative time synchronization system 300 includes a first vehicle-road cooperative time synchronization device 100 applied to vehicles in the vehicle-road cooperative system and a second vehicle-road cooperative time synchronization device 200 applied to roadside equipment in the vehicle-road cooperative system.

[0062] In this embodiment, the local time of the first vehicle-road cooperative time synchronization device 100 used in the vehicle-road cooperative system and the local time of the second vehicle-road cooperative time synchronization device 200 used in the roadside equipment of the vehicle-road cooperative system can be synchronized with UTC time when normal GPS signals can be obtained at the vehicle end or the roadside end. The error can be controlled within microseconds under normal operating conditions. Furthermore, there is a supporting solution to ensure that the local time of the vehicle-side perception system can be maintained even in special road sections without GPS signals, such as tunnels, preventing the continuous accumulation and expansion of errors. The deployment and implementation of this solution can solve the fundamental problems currently hindering vehicle-road cooperative perception fusion, laying a solid foundation for promoting vehicle-road cooperative perception fusion.

[0063] Therefore, those skilled in the art should recognize that although exemplary embodiments of the present invention have been shown and described in detail herein, many other variations or modifications conforming to the principles of the present invention can be directly determined or derived from the disclosure of the present invention without departing from the spirit and scope of the invention. Thus, the scope of the present invention should be understood and recognized as covering all such other variations or modifications.

Claims

1. A vehicle-road cooperative time synchronization method, applied to a vehicle in a vehicle-road cooperative system, the vehicle comprising an onboard GPS timing unit, an onboard NTP server, and multiple onboard sensor data processing units, wherein the onboard NTP server is connected to the onboard GPS timing unit and a first remote time server respectively, the onboard GPS timing unit being configured to provide a first GPS timing signal to the onboard NTP server when a GPS signal is normally acquired; the vehicle-road cooperative system further comprises roadside equipment, the roadside equipment including a vehicle-road cooperative NTP server; The vehicle-road cooperative time synchronization method includes: Determine whether the vehicle-mounted NTP server has received the first GPS timing signal; When the vehicle-mounted NTP server does not receive the first GPS timing signal, it simultaneously reads the NTP level information of the vehicle-road cooperative NTP server and the NTP level information of the first remote time server, and synchronizes the vehicle-mounted NTP server with the one with the lower level. After successful synchronization, a first synchronization command is sent to each of the vehicle-mounted sensor data processing units so that each of the vehicle-mounted sensor data processing units synchronizes the time of the vehicle-mounted NTP server via Network Time Protocol.

2. The vehicle-road cooperative time synchronization method according to claim 1, wherein, After determining whether the vehicle-mounted NTP server has received the first GPS timing signal, the method further includes: When the vehicle-mounted NTP server receives the first GPS timing signal, it synchronizes the GPS hardware reference time.

3. The vehicle-road cooperative time synchronization method according to claim 1 or 2, wherein, The vehicle-mounted GPS timing unit includes a connected integrated inertial navigation system and a signal expansion board. The signal expansion board is connected to the vehicle-mounted NTP server. The vehicle also includes a vehicle-mounted lidar connected to the signal expansion board to obtain the first GPS timing signal through the signal expansion board. The vehicle-road cooperative time synchronization method also includes: Determine whether the vehicle-mounted lidar has received the first GPS timing signal; When the vehicle-mounted lidar receives the first GPS timing signal, it synchronizes the vehicle-mounted lidar with the GPS hardware reference time.

4. The vehicle-road cooperative time synchronization method according to claim 3, wherein, After determining whether the vehicle-mounted lidar has received the first GPS timing signal, the method further includes: When the vehicle-mounted lidar does not receive the first GPS timing signal, the vehicle-mounted lidar synchronizes with the time of the onboard NTP server.

5. The vehicle-road cooperative time synchronization method according to claim 4, wherein, The step of synchronizing the time of the vehicle-mounted lidar with the time of the onboard NTP server when the vehicle-mounted lidar does not receive the first GPS timing signal includes: The transmission latency of the test node in the local area network where the vehicle-mounted lidar is located is detected when communicating with the vehicle-mounted NTP server. The test node is connected to the vehicle-mounted NTP server through a switch. The local time of the vehicle-mounted LiDAR is determined based on the transmission delay and the local time of the vehicle-mounted NTP server.

6. The vehicle-road cooperative time synchronization method according to claim 5, wherein, The steps for detecting the transmission delay when the test node in the local area network where the vehicle-mounted LiDAR is located communicates with the vehicle-mounted NTP server include: The vehicle-mounted NTP server transmits a first data packet carrying the first transmission time to the test node at the first transmission time, records the first reception time of the test node receiving the first data packet, and calculates the difference A2B between the first reception time and the first transmission time. The test node transmits a second data packet carrying the second transmission time to the vehicle-mounted NTP server at the second transmission time, records the second reception time of the vehicle-mounted NTP server receiving the second data packet, and calculates the difference B2A between the second reception time and the second transmission time. The clock offset C is calculated according to the following formula (1): C = (A2B - B2A) / 2 (1); The transmission delay is calculated according to the following formula (2). : =A2B –C (2)。 7. The vehicle-road cooperative time synchronization method according to claim 5, wherein, The steps for determining the local time of the vehicle-mounted LiDAR based on the transmission delay and the local time of the vehicle-mounted NTP server include: The vehicle-mounted NTP server sends a second synchronization command to the vehicle-mounted lidar at a third moment, and the second synchronization command carries the transmission delay. When the vehicle-mounted lidar receives the second synchronization command, the local time of the vehicle-mounted lidar is set to the sum of the third time point and the transmission delay.

8. The vehicle-road cooperative time synchronization method according to claim 1, wherein, The vehicle-road cooperative NTP server is timed by a roadside GPS timing unit or a second remote time server. When the vehicle-road cooperative NTP server is synchronized with the roadside GPS timing unit, the NTP level of the vehicle-road cooperative NTP server is lower than the NTP level of the first remote time server. The steps to synchronize the onboard NTP server with the lower-level of the two include: When the vehicle-road cooperative NTP server is timed by the roadside GPS timing unit, the vehicle-mounted NTP server is synchronized with the vehicle-road cooperative NTP server.

9. A vehicle-road cooperative time synchronization method, applied to roadside equipment in a vehicle-road cooperative system, the roadside equipment comprising a roadside GPS timing unit, a vehicle-road cooperative NTP server, and multiple roadside sensor data processing units, each of the roadside sensor data processing units being connected to the vehicle-road cooperative NTP server, the vehicle-road cooperative NTP server being provided with a second GPS timing signal by the roadside GPS timing unit or with timing from a second remote time server; the vehicle-road cooperative system further comprising a vehicle, the vehicle comprising an onboard GPS timing unit and an onboard NTP server respectively connected to the onboard GPS timing unit and a first remote time server, the onboard GPS timing unit being configured to provide a first GPS timing signal to the onboard NTP server when a GPS signal is normally acquired, the onboard NTP server being connected to the vehicle-road cooperative NTP server; The vehicle-road cooperative time synchronization method includes: Determine whether the vehicle-road cooperative NTP server has received the second GPS timing signal; When the vehicle-road cooperative NTP server receives the second GPS timing signal, the vehicle-road cooperative NTP server synchronizes the GPS hardware reference time. The system receives a synchronization request sent by the vehicle-mounted NTP server and responds to the synchronization request by providing a reference time to the vehicle-mounted NTP server for synchronization. The synchronization request is sent by the vehicle-mounted NTP server when it has not received the first GPS timing signal and the NTP level of the vehicle-road cooperative NTP server is lower than the NTP level of the first remote time server. A third synchronization command is sent to each of the roadside sensor data processing units so that each of the roadside sensor data processing units synchronizes the time of the vehicle-road cooperative NTP server via Network Time Protocol.

10. The vehicle-road cooperative time synchronization method according to claim 9, wherein, When the vehicle-road cooperative NTP server is timed by the roadside GPS timing unit, the NTP level of the vehicle-road cooperative NTP server is lower than the NTP level of the first remote time server.

11. The vehicle-road cooperative time synchronization method according to claim 9, further comprising, after determining whether the vehicle-road cooperative NTP server has received the second GPS timing signal: When the vehicle-road cooperative NTP server does not receive the second GPS timing signal, the vehicle-road cooperative NTP server synchronizes its time with the second remote time server.

12. A first vehicle-road cooperative time synchronization device, applied to a vehicle in a vehicle-road cooperative system, the first vehicle-road cooperative time synchronization device comprising an on-board GPS timing unit, an on-board NTP server, and multiple on-board sensor data processing units, a memory, and a processor, wherein the on-board NTP server is connected to the on-board GPS timing unit and a first remote time server respectively, and the memory stores a control program, which, when executed by the processor, is used to implement the vehicle-road cooperative time synchronization method according to any one of claims 1-8.

13. A second vehicle-road cooperative time synchronization device, applied to roadside equipment in a vehicle-road cooperative system, the second vehicle-road cooperative time synchronization device comprising a roadside GPS timing unit, a vehicle-road cooperative NTP server, multiple roadside sensor data processing units, a memory, and a processor, each of the roadside sensor data processing units being connected to the vehicle-road cooperative NTP server, the vehicle-road cooperative NTP server being provided with a second GPS timing signal by the roadside GPS timing unit or by a second remote time server, the memory storing a control program, the control program being executed by the processor to implement the vehicle-road cooperative time synchronization method according to any one of claims 9-11.

14. A vehicle-road cooperative time synchronization system, comprising the first vehicle-road cooperative time synchronization device as described in claim 12 and the second vehicle-road cooperative time synchronization device as described in claim 13.

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