CN116830487A - Vehicle-road cooperation time synchronization method, vehicle-road cooperation time synchronization device and system - Google Patents
Vehicle-road cooperation time synchronization method, vehicle-road cooperation time synchronization device and system Download PDFInfo
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- H04W4/00—Services specially adapted for wireless communication networks; Facilities therefor
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- H04W4/40—Services specially adapted for particular environments, situations or purposes for vehicles, e.g. vehicle-to-pedestrians [V2P]
- H04W4/44—Services specially adapted for particular environments, situations or purposes for vehicles, e.g. vehicle-to-pedestrians [V2P] for communication between vehicles and infrastructures, e.g. vehicle-to-cloud [V2C] or vehicle-to-home [V2H]
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Abstract
A vehicle-road cooperative time synchronization method, a vehicle-road cooperative time synchronization device and a system belong to the field of time synchronization. The vehicle-road cooperative time synchronization method comprises the following steps: judging whether the vehicle-mounted NTP server (20) receives a first GPS time service signal (S100); when the vehicle-mounted NTP server (20) does not receive the first GPS time service signal, simultaneously reading NTP level information of the vehicle-mounted cooperative NTP server (70) and NTP (50) level information of a first remote time server, and synchronizing the vehicle-mounted NTP server (20) with the lower level of the vehicle-mounted NTP server and the first remote time server (S200); after the synchronization is successful, a first synchronization instruction is sent to each in-vehicle sensor data processing unit (80) so that each in-vehicle sensor data processing unit (80) synchronizes the time of the in-vehicle NTP server (20) through the network time protocol (S300). The vehicle-road cooperative time synchronization method, the synchronization device and the system can meet the automatic driving requirement.
Description
The present 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 a system.
In the current system framework of vehicle-road collaborative driving, a vehicle-mounted sensing system and a road side sensing system are relatively independent, and it is very difficult to fully utilize sensing information of a vehicle and a road side to realize more comprehensive and accurate sensing. At present, the traditional scheme takes a vehicle-mounted sensing system as a main part and takes a road side sensing system as an auxiliary part, and in a low-level automatic driving function, the information provided by the road side sensing system is only used for reminding and warning a driver; the perception information actually participating in decision control in the high-level automatic driving function is still provided by the vehicle-mounted perception system, and only intersection traffic signal lamp information is used for decision planning in the perception information provided by the road side perception system. The perceived information provided by the road side perceived system has very low proportion and weight in the decision, and the reasons for the phenomenon are as follows: 1. the existing road side sensing system has few sensor types and small quantity, and the sensing range cannot cover the intersection in all directions; 2. the reason why the road side sensing cannot be subjected to data fusion with the vehicle sensing is that the road side sensing system is not subjected to time synchronization with the vehicle sensing system. Considering a common scenario, the vehicle-mounted sensing system and the road side sensing system are independent and respectively have a clock source, and the bias of a vehicle end and a road side time source is unknown. For the same target, the vehicle-mounted sensor is arranged on The target is perceived at the moment, and the time delay tau is processed and transmitted through an algorithm veh Then the data are transmitted to a perception fusion module; meanwhile, the road side sensor is arranged atThe same target is perceived at the moment, and the time delay tau is processed and transmitted through an algorithm road And then the data are transmitted to a perception fusion module. The fusion module can not fuse the two frames of target information, and the following reasons are: 1. the perception fusion module can not judge the actual sequence relation of the two frames of target information; 2. the actual time difference of the two frames of target information cannot be obtained by the perception fusion module. The practical effect is that for the same object there are multiple ghosts, i.e. a single object is perceived as multiple objects.
The traditional automatic driving time synchronization scheme only considers a vehicle-mounted sensor system, one master clock is selected from a plurality of vehicle-mounted CPU (Central processing Unit) computing units, other sensors serve as slave clocks to synchronize the master clock through an in-vehicle local area network, and no specific requirement is imposed on the selection of the master clock. This is possible in the case of bicycle intelligence, because the in-car local area network of bicycle is simple in structure, and the sensor does not need to pass through the route with CPU computing element communication, and transmission delay is little and stable. However, in the framework of vehicle-road coordination, the disadvantage of this solution is that the roadside sensor cannot be incorporated into the time synchronization system, because the communication link between the roadside sensor and the on-board CPU computing unit is complex and variable, and the wireless transmission is unstable. If the clocks of the sensors on the road side are synchronized by the same scheme, the time synchronization effect of the sensors on the road side and the vehicle-mounted CPU computing unit cannot reach the same time synchronization effect of the vehicle-mounted sensors and the vehicle-mounted CPU computing unit under the influence of the network environment, and the automatic driving requirement cannot be met.
Disclosure of Invention
In view of the foregoing, the present invention has been made to provide a vehicle-road cooperative time synchronization method, a vehicle-road cooperative time synchronization apparatus, and a system that overcome or at least partially solve the foregoing problems.
An object of the first aspect of the present invention is to provide a vehicle-road cooperation time synchronization method applied to a vehicle of a vehicle-road cooperation system, capable of meeting an automatic driving requirement.
Another object of the invention is to achieve time synchronization of the vehicle and the road side equipment, controlling the actual error on the order of microseconds.
An object of the second aspect of the present invention is to provide a vehicle-road cooperation time synchronization method applied to a road side device of a vehicle-road cooperation system, which can meet an automatic driving requirement.
An object of the third aspect of the present invention is to provide a vehicle-road cooperation time synchronization device for a vehicle of a vehicle-road cooperation system, capable of meeting an automatic driving requirement.
An object of the fourth aspect of the present invention is to provide a vehicle-road cooperation time synchronization device applied to a road side apparatus of a vehicle-road cooperation system, capable of meeting an automatic driving requirement.
An object of the fifth aspect of the present invention is to provide a vehicle-road collaborative time synchronization system, so as to solve the basic problem that the vehicle-road collaborative sensing fusion is plagued at present, and lay a solid foundation for propulsion of the vehicle-road collaborative sensing fusion.
Particularly, according to a first aspect of an embodiment of the present invention, there is provided a vehicle-road cooperative time synchronization method, applied to a vehicle of a vehicle-road cooperative system, where the vehicle includes a vehicle-mounted GPS time service unit, a vehicle-mounted NTP server, and a plurality of vehicle-mounted sensor data processing units, where the vehicle-mounted NTP server is connected to the vehicle-mounted GPS time service unit and a first remote time server, respectively, and the vehicle-mounted GPS time service unit is configured to provide a first GPS time service signal to the vehicle-mounted NTP server when a GPS signal is normally acquired; the vehicle-road cooperation system further comprises road side equipment, wherein the road side equipment comprises a vehicle-road cooperation NTP server;
the vehicle-road cooperative time synchronization method comprises the following steps:
judging whether the vehicle-mounted NTP server receives the first GPS time service signal or not;
when the vehicle-mounted NTP server does not receive the first GPS time service signal, NTP level information of the vehicle-mounted NTP server and NTP level information of the first remote time server are read at the same time, and the vehicle-mounted NTP server is synchronized with the lower level of the vehicle-mounted NTP server and the lower level of the vehicle-mounted NTP server;
after the synchronization is successful, a first synchronization instruction is sent to each vehicle-mounted sensor data processing unit, so that each vehicle-mounted sensor data processing unit synchronizes the time of the vehicle-mounted NTP server through a network time protocol.
Optionally, after the step of determining whether the vehicle-mounted NTP server receives the first GPS time service signal, the method further includes:
and enabling the vehicle-mounted NTP server to synchronize GPS hardware reference time when the vehicle-mounted NTP server receives the first GPS time service signal.
Optionally, the vehicle-mounted GPS time service unit includes a combined inertial navigation system and a signal expansion board, where the signal expansion board is connected to the vehicle-mounted NTP server, and the vehicle further includes a vehicle-end laser radar connected to the signal expansion board, so as to obtain the first GPS time service signal through the signal expansion board;
the vehicle-road cooperative time synchronization method further comprises the following steps:
judging whether the vehicle-end laser radar receives the first GPS time service signal or not;
and enabling the vehicle-end laser radar to synchronize GPS hardware reference time when the vehicle-end laser radar receives the first GPS time service signal.
Optionally, after the step of determining whether the vehicle-end laser radar receives the first GPS time service signal, the method further includes:
and enabling the vehicle-end laser radar to synchronize the time of the vehicle-mounted NTP server when the vehicle-end laser radar does not receive the first GPS time service signal.
Optionally, the step of synchronizing the time of the vehicle-end lidar with the vehicle-mounted NTP server when the vehicle-end lidar does not receive the first GPS time service signal includes:
detecting transmission delay when a test node in a local area network where the vehicle-end laser radar is positioned communicates with the vehicle-mounted NTP server, wherein the test node is connected with the vehicle-mounted NTP server through a switch;
and determining the local time of the vehicle-end laser radar according to the transmission time delay and the local time of the vehicle-mounted NTP server.
Optionally, the step of detecting a transmission delay when the test node in the local area network where the vehicle-end laser radar is located communicates with the vehicle-mounted NTP server includes:
transmitting a first data packet carrying the first transmission time from the vehicle-mounted NTP server to the test node at the first transmission time, recording a first receiving time when the test node receives the first data packet, and calculating a difference A2B between the first receiving time and the first transmission time;
transmitting a second data packet carrying the second transmission time from the test node to the vehicle-mounted NTP server at the second transmission time, recording a second receiving time when the vehicle-mounted NTP server receives the second data packet, and calculating a difference B2A between the second receiving time and the second transmission time;
The clock offset C is calculated according to the following equation (1):
C＝(A2B-B2A)/2 (1)；
the transmission delay DeltaT' is calculated according to the following formula (2):
ΔT^'＝A2B–C (2)。
optionally, the step of determining the local time of the vehicle-end laser radar according to the transmission delay and the local time of the vehicle-mounted NTP server includes:
a second synchronous instruction is sent to the vehicle-mounted laser radar from the vehicle-mounted NTP server at a third moment, and the second synchronous instruction carries the transmission delay;
and setting the local time of the vehicle-mounted laser radar as the sum of the third moment and the transmission delay when the vehicle-mounted laser radar receives the second synchronous command.
Optionally, the vehicle-road cooperation NTP server is time-stamped by a road side GPS time-stamping unit or the second remote time server;
when the vehicle-road cooperative NTP server is taught by the road side GPS time service unit, the NTP level of the vehicle-road cooperative NTP server is lower than that of the first remote time server;
the step of synchronizing the in-vehicle NTP server with the lower of the two levels includes:
and synchronizing the vehicle-mounted NTP server with the vehicle-road cooperative NTP server when the vehicle-road cooperative NTP server is taught by the road side GPS timing unit.
In particular, according to a second aspect of the embodiment of the present invention, there is provided a vehicle-road cooperation time synchronization method, which is applied to a road side device of a vehicle-road cooperation system, where the road side device includes a road side GPS time service unit, a vehicle-road cooperation NTP server, and a plurality of road side sensor data processing units, each of the road side sensor data processing units is connected to the vehicle-road cooperation NTP server, and the vehicle-road cooperation NTP server is provided with a second GPS authorization signal by the road side GPS time service unit or is time-serviced by a second remote time server; the vehicle-road cooperation system further comprises a vehicle, the vehicle comprises a vehicle-mounted GPS time service unit and a vehicle-mounted NTP server, the vehicle-mounted GPS time service unit is configured to provide a first GPS time service signal for the vehicle-mounted NTP server when a GPS signal is normally acquired, and the vehicle-mounted NTP server is connected with the vehicle-road cooperation NTP server;
the vehicle-road cooperative time synchronization method comprises the following steps:
the vehicle-road cooperative time synchronization method comprises the following steps:
judging whether the vehicle-road cooperative NTP server receives the second GPS time service signal or not;
when the vehicle-road cooperative NTP server receives the second GPS time service signal, enabling the vehicle-road cooperative NTP server to synchronize GPS hardware reference time;
Receiving a synchronization request sent by the vehicle-mounted NTP server, and providing reference time for the vehicle-mounted NTP server for synchronization in response to the synchronization request, wherein the synchronization request is sent by the vehicle-mounted NTP server when the first GPS time service signal is not received and the NTP level of the vehicle-mounted cooperative NTP server is lower than the NTP level of the first remote time server;
and sending a third synchronization instruction to each road side sensor data processing unit so that each road side sensor data processing unit synchronizes the time of the vehicle-road cooperative NTP server through a network time protocol.
Optionally, when the vehicle-road cooperative NTP server is taught by the road-side GPS time service unit, an NTP level of the vehicle-road cooperative NTP server is lower than an NTP level of the first remote time server.
Optionally, after determining whether the vehicle-road coordination NTP server receives the second GPS time service signal, the method further includes:
and synchronizing the time of the second remote time server by the vehicle-road cooperative NTP server when the vehicle-road cooperative NTP server does not receive the second GPS time service signal.
In particular, according to a third aspect of an embodiment of the present invention, there is provided a first vehicle-road cooperative time synchronization apparatus applied to a vehicle of a vehicle-road cooperative system, the vehicle-road cooperative time synchronization apparatus including a vehicle-mounted GPS time service unit, a vehicle-mounted NTP server, and a plurality of vehicle-mounted sensor data processing units, a memory, and a processor, the vehicle-mounted NTP server being respectively connected to the vehicle-mounted GPS time service unit and a first remote time server, the memory storing a control program, which when executed by the processor is used to implement a vehicle-road cooperative time synchronization method according to any one of the above-described vehicles applied to the vehicle-road cooperative system.
In particular, according to a fourth aspect of the embodiment of the present invention, there is provided a second vehicle-road cooperation time synchronization apparatus applied to a road side device of a vehicle-road cooperation system, where the vehicle-road cooperation time synchronization apparatus includes a road side GPS time service unit, a vehicle-road cooperation NTP server, a plurality of road side sensor data processing units, a memory, and a processor, each of the road side sensor data processing units is connected to the vehicle-road cooperation NTP server, the vehicle-road cooperation NTP server is provided with a second GPS authorization signal by the road side GPS time service unit or is time-shared by a second remote time server, and a control program is stored in the memory, where the control program is executed by the processor and is used to implement a vehicle-road cooperation time synchronization method according to the road side device applied to the vehicle-road cooperation system.
In particular, according to a fifth aspect of an embodiment of the present invention, there is provided a vehicle-road cooperative time synchronization system including a first vehicle-road cooperative time synchronization device and a second vehicle-road cooperative time synchronization device.
According to the vehicle-road cooperative time synchronization method, when the vehicle-mounted NTP server receives the first GPS time service signal, the vehicle-mounted NTP server synchronizes GPS hardware reference time, so that accurate UTC time is obtained. Under the condition that the vehicle-mounted NTP server does not receive the first GPS time service signal, the vehicle-mounted NTP server can obtain more accurate time by providing time for the lower-level one of the vehicle-mounted NTP server and the first remote time server, and the local time error of the vehicle-mounted NTP server is ensured not to be accumulated along with time. In particular, when the vehicle-mounted NTP server cannot acquire the first GPS time service signal, accurate time can be acquired from the vehicle-mounted cooperative NTP server capable of acquiring the second GPS authorization signal, so that the error between the time of the automatic driving system of the whole vehicle end and UTC time can be controlled at microsecond level, and the requirement of vehicle-mounted cooperative automatic driving is met.
Furthermore, in the method, GPS time service signals (UTC time and PPS signals) are expanded through the combination of the inertial navigation system and the signal expansion board and are provided for each laser radar and the vehicle-mounted NTP server, so that each laser radar and the vehicle-mounted NTP server can acquire accurate GPS time service signals.
Further, in the method, when the vehicle-mounted laser radar cannot receive accurate and reliable hardware reference time and supports a mode of configuring local time by sending instructions through an Ethernet port, the error of the vehicle-mounted laser radar and a time source can be kept by testing transmission time delay and further determining the local time of the vehicle-mounted laser radar according to the transmission time delay and the local time of the vehicle-mounted NTP server.
The foregoing description is only an overview of the present invention, and is intended to be implemented in accordance with the teachings of the present invention in order that the same may be more clearly understood and to make the same and other objects, features and advantages of the present invention more readily apparent.
The above, as well as additional objectives, advantages, and features of the present invention will become apparent to those skilled in the art from the following detailed description of a specific embodiment of the present invention when read in conjunction with the accompanying drawings.
Some specific embodiments of the invention will be described in detail hereinafter by way of example and not by way of limitation with reference to the accompanying drawings. The same reference numbers will be used throughout the drawings to refer to the same or like parts or portions. It will be appreciated by those skilled in the art that the drawings are not necessarily drawn to scale. In the accompanying drawings:
FIG. 1 is a flow chart of a vehicle-road cooperative time synchronization method applied to a vehicle of a vehicle-road cooperative system according to an embodiment of the present invention;
FIG. 2 is a connection block diagram of a vehicle applied to a vehicle road collaboration system according to one embodiment of the invention;
FIG. 3 is a flow chart of a vehicle-road cooperative time synchronization method applied to a vehicle of a vehicle-road cooperative system according to another embodiment of the present invention;
FIG. 4 is a flow chart of a vehicle-road cooperative time synchronization method applied to a road side device of a vehicle-road cooperative system according to an embodiment of the present invention;
FIG. 5 is a connection block diagram of a roadside device applied to a vehicle-road cooperative system according to one embodiment of the present invention;
fig. 6 is a schematic diagram of NTP timing between a client and a server;
fig. 7 is a connection block diagram of a vehicle-road cooperative time synchronization system according to an embodiment of the present invention.
Exemplary embodiments of the present disclosure will be described in more detail below 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 embodied 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.
Fig. 1 is a flowchart of a vehicle-road cooperation time synchronization method applied to a vehicle of a vehicle-road cooperation system according to an embodiment of the present invention. Fig. 2 is a connection block diagram of a vehicle applied to a road cooperation system according to an embodiment of the present invention. The vehicle-road cooperation time synchronization method is applied to a vehicle of a vehicle-road cooperation system, and the vehicle-road cooperation system comprises a vehicle and road side equipment. As shown in fig. 2, the vehicle includes a vehicle-mounted GPS time service unit 10, a vehicle-mounted NTP server 20, and a plurality of vehicle-mounted sensor data processing units 30, where the vehicle-mounted NTP server 20 is connected to the vehicle-mounted GPS time service unit 10 and a first remote time server 50, respectively, and the vehicle-mounted GPS time service unit 10 is configured to provide a first GPS time service signal to the vehicle-mounted NTP server 20 when a GPS signal is normally acquired. The lengths of the wires for transmitting the first GPS time service signal should be as short and the same as possible, so as to ensure that the time delay caused by the transmission of the wires is as small and the same as possible, thereby ensuring the accuracy of the first GPS time service signal, which is easy to realize at the vehicle end. The in-vehicle GPS time service unit 10 can provide a pulse per second signal (PPS) and a UTC time service signal, and the time in the UTC time service signal corresponds to the rising edge of the PPS signal, and the in-vehicle NTP server 20 is a device of the vehicle where the NTP service is deployed, and can update the time of the in-vehicle GPS time service unit to the UTC time at the timing of the rising edge of the PPS signal. Alternatively, the in-vehicle sensor data processing unit 30 includes a general-purpose processing unit 31 corresponding to millimeter wave radar, ultrasonic radar, chassis sensor, and the like, and a special-purpose processing unit 32 corresponding to a camera. The roadside devices include a vehicle-road cooperative NTP server 70. The vehicle-road cooperative NTP server 70 is time-stamped by the road-side GPS time stamping unit 60 or the second remote time stamping server 90. The roadside GPS time service unit 60 provides the vehicle-road cooperative NTP server 70 with a second GPS time service signal when the GPS signal is normally acquired.
As shown in fig. 1, the vehicle-road cooperative time synchronization method in this embodiment includes:
step S100, it is determined whether the vehicle-mounted NTP server 20 receives the first GPS time service signal, and if not, the process proceeds to step S200.
In step S200, the NTP hierarchy information of the vehicle-mounted NTP server 70 and the NTP hierarchy information of the first remote time server 50 are read simultaneously, and the vehicle-mounted NTP server 20 is synchronized with the lower hierarchy of the two. When the vehicle-mounted NTP server 70 is time-stamped by the roadside GPS time stamping unit 60, the NTP hierarchy of the vehicle-mounted NTP server 70 is lower than the NTP hierarchy of the first remote time server 50, and the vehicle-mounted NTP server 20 and the vehicle-mounted NTP server 70 are synchronized. When the vehicle-mounted NTP server 70 is taught by the second remote time server 90, then it is still necessary to determine the synchronization object of the vehicle-mounted NTP server 20 according to the NTP hierarchy in the first remote time server 50 and the vehicle-mounted NTP server 70. Since the hierarchy of the first remote time server 50 and the second remote time server 90 is determined by how far and near itself is from the GPS time node, i.e., the further from the GPS node, the higher the hierarchy is. Therefore, according to the determined hierarchy information of the first remote time server 50 and the second remote time server 90 in the actual situation, the NTP hierarchy sizes of the first remote time server 50 and the vehicle-mounted NTP server 70 can be determined, for example, the NTP hierarchy of the first remote time server 50 is 3, the NTP hierarchy of the second remote time server 90 is 3, the NTP hierarchy of the vehicle-mounted NTP server 20 is 4, and the first remote time server 50 with the lower NTP hierarchy is selected by the vehicle-mounted NTP server 20 for time synchronization.
In step S300, after the synchronization is successful, a first synchronization instruction is sent to each in-vehicle sensor data processing unit 30, so that each in-vehicle sensor data processing unit 30 synchronizes the time of the in-vehicle NTP server 20 through the network time protocol.
When the autonomous vehicle runs in an area such as a tunnel where satellite signals cannot be received, the vehicle-mounted GPS time service unit 10 cannot normally acquire GPS signals, the vehicle-mounted NTP server 20 cannot acquire accurate and reliable UTC time by receiving the first GPS time service signal, and an error between the local time of the vehicle-mounted NTP server 20 and the UTC time increases as the time when the vehicle-mounted GPS time service unit 10 cannot normally acquire GPS signals increases. The vehicle-mounted NTP server 20 of the present embodiment can access the vehicle-road cooperative NTP server 70 at the road side, and the vehicle-mounted NTP server 20 can be connected with the first remote time server 50, so that the time can be obtained from the vehicle-road cooperative NTP server 70 and the first remote time server 50, and one synchronization time with a lower hierarchy (i.e. more accurate) can be selected. Generally, the vehicle-road cooperative NTP server 70 can provide the second GPS authorization signal through the road-side GPS time service unit 60, and when the vehicle-mounted NTP server 20 cannot receive the first GPS time service signal through the vehicle-mounted GPS time service unit 10 of the vehicle, the vehicle-road cooperative NTP server 70 can provide accurate time, at this time, the NTP level of the vehicle-road cooperative 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, there may be situations where the vehicle-mounted NTP server 70 cannot provide accurate time, such as signal interruption, equipment failure, etc., at which time the vehicle-mounted NTP server 20 may also perform time synchronization through the first remote time server 50. Therefore, in the case that the vehicle-mounted NTP server 20 at the vehicle end does not receive the first GPS time service signal, the vehicle-mounted NTP server 20 can obtain more accurate time by providing time for the lower-level one of the vehicle-mounted NTP server 70 and the first remote time server 50, so as to ensure that the local time error of the vehicle-mounted NTP server 20 is not accumulated with time. In particular, when the vehicle-mounted NTP server 20 cannot acquire the first GPS time service signal, the vehicle-mounted NTP server 70 can still acquire accurate time from the vehicle-mounted cooperative NTP server capable of acquiring the second GPS authorization signal, so that the error between the time of the automatic driving system of the whole vehicle end and the UTC time can be controlled to be in the microsecond level, and the requirement of vehicle-mounted cooperative automatic driving is met.
Of course, when the on-board NTP server 20 cannot acquire the accurate time signal (i.e., when the on-board NTP server 20 cannot acquire the first GPS time signal from the on-board GPS time service unit 10 and the on-board cooperative NTP server 70 does not acquire the second GPS time signal), the on-board NTP server 20 can only acquire time from the first remote time server 50 or from the on-board cooperative NTP server 70 (when the on-board cooperative NTP server 70 synchronizes time from the second remote time server 90), although the time error of the on-board NTP server 20 can be maintained, the error level inevitably decreases from the microsecond level to the millisecond level, in which case the false detection introduced by the on-board cooperative sensing fusion increases substantially, so that the automatic driving mode is switched from on-board cooperative to single-board intelligent.
In one embodiment, as shown in fig. 1, step S100 further includes:
in step S400, the on-board NTP server 20 is synchronized with the GPS hardware reference time when the on-board NTP server 20 receives the first GPS time service signal. It is understood that the in-vehicle NTP server 20 preferentially synchronizes the time from the in-vehicle GPS timing unit 10 of the vehicle, thereby acquiring accurate UTC time.
Fig. 3 is a flowchart of a vehicle-road cooperation time synchronization method applied to a vehicle of a vehicle-road cooperation system according to another embodiment of the present invention. In another embodiment, as shown in fig. 2, the vehicle-mounted GPS time service unit 10 includes a combined inertial navigation system 11 and a signal expansion board 12, where the combined inertial navigation system 11 may be a combined inertial navigation system 11 of a vehicle and has a GPS receiving module. The signal expansion board 12 is connected to the on-board NTP server 20, and the vehicle further includes a vehicle-end lidar 40 connected to the signal expansion board 12 to obtain a first GPS time service signal through the signal expansion board 12.
As shown in fig. 3, in this embodiment, the vehicle-road collaboration time synchronization method further includes:
step S500, judging whether the vehicle-end laser radar 40 receives the first GPS time service signal, if yes, proceeding to step S600, otherwise proceeding to step S700.
Step S600, the vehicle-end lidar 40 is synchronized with the GPS hardware reference time.
In step S700, the vehicle-side lidar 40 synchronizes the time of the on-vehicle NTP server 20.
For the lidars generated by the mainstream lidar manufacturers at present, the GPS time service interface is provided, and the time synchronization can be realized by receiving hardware reference time, in this embodiment, the combined inertial navigation system 11 extends GPS time service signals (UTC time and PPS signals) through the signal extension board 12, and provides the GPS time service signals 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 time service signals.
In a further embodiment, as shown in fig. 3, step S700 includes:
in step S701, a transmission delay when a test node in the local area network where the vehicle-end lidar 40 is located communicates with the on-vehicle NTP server 20 is detected, and the test node is connected with the on-vehicle NTP server 20 through a switch.
In step S702, the local time of the vehicle-end lidar 40 is determined according to the transmission delay and the local time of the on-board NTP server 20.
Further, step S701 includes:
transmitting a first data packet carrying the first sending time from the vehicle-mounted NTP server 20 to the test node at the first sending time, recording the first receiving time of the test node for receiving the first data packet, and calculating a difference A2B between the first receiving time and the first sending time;
transmitting a second data packet carrying the second sending moment from the test node to the vehicle-mounted NTP server 20 at the second sending moment, recording a second receiving moment when the vehicle-mounted NTP server 20 receives the second data packet, and calculating a difference B2A between the second receiving moment and the second sending moment;
the clock offset C is calculated according to the following equation (1):
C＝(A2B-B2A)/2 (1)
the transmission delay deltat' is calculated according to the following equation (2):
ΔT′＝A2B–C (2)
step S702 includes: a second synchronization instruction is sent to the vehicle-mounted laser radar from the vehicle-mounted NTP server 20 at a third moment, and the second synchronization instruction carries transmission delay; when the vehicle-mounted laser radar receives the second synchronous command, setting the local time of the vehicle-mounted laser radar as the sum of the third moment and the transmission delay, namely
T sync ＝T+ΔT′ (3)
Wherein T is sync And the local time of the vehicle-mounted laser radar is T which is the third time.
On the premise that the vehicle-mounted communication network structure is not changed, the transmission delay of the vehicle-mounted laser radar is considered to be the same as the transmission delay of the test node, so that the calculated transmission delay of the test node is used as the transmission delay of the vehicle-mounted laser radar in the embodiment. Since the transmission protocol of the in-vehicle lidar is different from that of the in-vehicle network, the time of the in-vehicle NTP server 20 cannot be synchronized directly by the NTP protocol. When the vehicle-mounted laser radar cannot receive accurate and reliable hardware reference time and supports a mode of configuring local time by sending instructions through an Ethernet port, the error between the vehicle-mounted laser radar and a time source is kept through the method. The simple command transmission time in the vehicle-mounted local area network is generally in the microsecond level, and the error between the local time of the vehicle-mounted laser radar and UTC time can be controlled within microsecond when the satellite signal is absent through the method.
Fig. 4 is a flowchart of a vehicle-road cooperation time synchronization method applied to a road side device of a vehicle-road cooperation system according to an embodiment of the present invention. Fig. 5 is a connection block diagram of a roadside apparatus applied to a vehicle-road cooperation system according to one embodiment of the present invention. In one embodiment, as shown in fig. 5, the roadside device includes a roadside GPS time service unit 60, a vehicle-road cooperative NTP server 70, and a plurality of roadside sensor data processing units 80, where each roadside sensor data processing unit 80 is connected to the vehicle-road cooperative NTP server 70, and the vehicle-road cooperative NTP server 70 is provided with a second GPS authorization signal by the roadside GPS time service unit 60 or is time-serviced by a second remote time server 90. Alternatively, the plurality of roadside sensor data processing units 80 include a plurality of cameras and millimeter wave radar-corresponding general-purpose processing units 81 arranged on the roadside and a plurality of laser radar-corresponding special-purpose processing units 82 arranged on the roadside. The vehicle-road cooperation system further comprises a vehicle, the vehicle comprises a vehicle-mounted GPS time service unit 10 and a vehicle-mounted NTP server 20, the vehicle-mounted GPS time service unit 10 is configured to provide a first GPS time service signal for the vehicle-mounted NTP server 20 when the GPS signal is normally acquired, and the vehicle-mounted NTP server 20 is connected with the vehicle-road cooperation NTP server 70.
As shown in fig. 4, in this embodiment, a vehicle-road cooperation time synchronization method applied to a road side device of a vehicle-road cooperation system includes:
in step S110, it is determined whether the vehicle-road coordination NTP server 70 receives the second GPS time service signal. If yes, go to step S120; otherwise, the process advances to step S130.
In step S120, the vehicle-road cooperation NTP server 70 synchronizes the GPS hardware reference time. Step S140 is then performed.
In step S130, the vehicle-road cooperative NTP server 70 synchronizes the time of the second remote time server 90.
In step S140, a synchronization request sent by the on-board NTP server 20 is received, and a reference time is provided for the on-board NTP server 20 for synchronization in response to the synchronization request, wherein the synchronization request is sent by the on-board NTP server 20 when the first GPS time service signal is not received and the NTP level of the on-board cooperative NTP server 70 is lower than the NTP level of the first remote time server 50. When the vehicle-road cooperative NTP server 70 is time-stamped by the road-side GPS time stamping unit 60, the NTP hierarchy of the vehicle-road cooperative NTP server 70 is lower than that of the first remote time server 50. When the vehicle-road cooperative NTP server 70 is authorized by the second remote time server 90, the NTP hierarchy sizes in the first remote time server 50 and the vehicle-road cooperative NTP server 70 need to be determined according to the NTP hierarchy sizes of the first remote time server 50 and the second remote time server 90, and the determination of specific sizes is already described in detail in the foregoing step S200, which is not repeated herein.
In step S150, a third synchronization instruction is sent to each of the roadside sensor data processing units 80, so that each of the roadside sensor data processing units 80 synchronizes the time of the vehicle-road cooperation NTP server 70 through the network time protocol. The execution sequence of step S140 and step S150 is not sequential here.
The vehicle-road cooperation NTP server 70 in the present embodiment preferentially obtains time by the road-side GPS time service unit 60, and obtains time by the second remote time server 90 when the road-side GPS time service unit 60 cannot obtain time. Because the roadside GPS timing unit 60 is usually located in an open area, accurate satellite timing can be obtained with a high probability, and high accuracy of time in the vehicle-road cooperation NTP server 70 is ensured. In addition, the vehicle-road cooperation NTP server 70, which is time-stamped by the road-side GPS time-stamping unit 60, can also provide time for the vehicle-mounted NTP server 20, which cannot time-stamped by the vehicle-mounted GPS time-stamping unit 10, so that both the vehicle end and the road end can obtain accurate time, and the accurate synchronization of the clocks of the vehicle end and the road end can be ensured, so as to meet the requirement of automatic driving.
It should be noted that, since the vehicle-mounted lidar can freely set the test node in the ethernet, the time can be configured through the ethernet (step S701 and step S702), and the lidar in the roadside device is usually provided by a third party, so that the test node cannot be freely set, and a dedicated data processor of the lidar needs to be set to synchronize the vehicle-road cooperation NTP server 70.
Fig. 6 is a schematic diagram of NTP timing between a client and a server. As shown in fig. 6, a client (client) first sends an NTP message to a server (server), where the NTP message includes a timestamp T1 of the message leaving the client, and when the server receives the message, the timestamp T2 of the message arrival and the timestamp T3 of the message leaving are sequentially filled in, and then immediately returns the message to the client. When the client receives the response message, the time stamp T4 returned by the message is recorded. The client can calculate 2 key parameters using the 4 time parameters described above: the round trip delay d of NTP messages and the clock skew t between client and server. The client uses the clock bias to adjust the local clock so that its time coincides with the server time.
Now, based on T1, T2, T3, T4 that have been obtained, it is desirable to find T to adjust the client-side clock:
assuming that the NTP request and reply message transmission delays are equal, i.e., d1=d2, substitution into equation (4) can be solved:
according to formula (4), t may also be expressed as
t＝(T2-T1)+d1＝(T2-T1)+d/2 (6)
It can be seen that T, d are only related to the difference T2, T1 and the difference T3, T4, and not related to the difference T2, T3, i.e. the final result is not related to the time required by the server to process the request. Therefore, the client can calculate the time difference T through T1, T2, T3, T4 to adjust the local clock.
The time synchronization between any two devices requiring time synchronization in the present invention can be achieved according to the above principle.
As shown in fig. 2, the first vehicle-path cooperative time synchronization device 100 applied to the vehicle of the vehicle-path cooperative system in the present embodiment includes a vehicle-mounted GPS time service unit 10, a vehicle-mounted NTP server 20, and a plurality of vehicle-mounted sensor data processing units 30, a memory, and a processor, where the vehicle-mounted NTP server 20 is connected to the vehicle-mounted GPS time service unit 10 and the first remote time server 50, respectively. Further, the vehicle-mounted GPS time service unit 10 comprises a combined inertial navigation system 11 and a signal expansion board 12 which are connected, and the signal expansion board 12 is connected with a vehicle-mounted NTP server 20. The first vehicle-road cooperative time synchronization apparatus 100 further includes a vehicle-end lidar 40 connected to the signal expansion board 12, and a control program is stored in the memory, where the control program is used to implement the vehicle-road cooperative time synchronization method applied to the vehicle-road cooperative system when executed by the processor. The processor may be a central processing unit (central processing unit, CPU for short), or a digital processing unit or the like. The processor transmits and receives data through the communication interface. The memory is used for storing programs executed by the processor. The memory is any medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer, and can be a combination of multiple memories. The above-described computer program may be downloaded from a computer readable storage medium to a corresponding computing/processing device or downloaded to a computer or an external memory device via a network (e.g., the internet, a local area network, a wide area network, and/or a wireless network).
As shown in fig. 5, the second vehicle road cooperation time synchronization apparatus 200 applied to the road side device of the vehicle road cooperation system of the present embodiment includes a road side GPS time service unit 60, a vehicle road cooperation NTP server 70, a plurality of road side sensor data processing units 80, a memory and a processor. Each of the road side sensor data processing units 80 is connected to the vehicle-road cooperative NTP server 70, where the vehicle-road cooperative NTP server 70 is provided with a second GPS authorization signal by the road side GPS time service unit 60 or is time-service by the second remote time server 90, and a control program is stored in the memory, where the control program is used to implement the vehicle-road cooperative time synchronization method applied to the road side device according to any embodiment or combination of embodiments when the control program is executed by the processor. The processor may be a central processing unit (central processing unit, CPU for short), or a digital processing unit or the like. The processor transmits and receives data through the communication interface. The memory is used for storing programs executed by the processor. The memory is any medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer, and can be a combination of multiple memories. The above-described computer program may be downloaded from a computer readable storage medium to a corresponding computing/processing device or downloaded to a computer or an external memory device via a network (e.g., the internet, a local area network, a wide area network, and/or a wireless network).
Fig. 7 is a connection block diagram of a vehicle-road cooperative time synchronization system 300 according to an embodiment of the present invention. As shown in fig. 7, in the present embodiment, the vehicle-road cooperative time synchronization system 300 includes a first vehicle-road cooperative time synchronization device 100 applied to a vehicle of the vehicle-road cooperative system and a second vehicle-road cooperative time synchronization device 200 applied to a road side apparatus of the vehicle-road cooperative system.
In this embodiment, the local time of the first vehicle-road cooperation time synchronization device 100 applied to the vehicle of the vehicle-road cooperation system and the local time of the second vehicle-road cooperation time synchronization device 200 applied to the road side equipment of the vehicle-road cooperation system can be synchronized with UTC time when the vehicle end or the road side end can acquire a normal GPS signal, and the error can be controlled at microsecond level under the normal working condition. The deployment implementation of the scheme can solve the basic problem of the current trouble of vehicle-road collaborative perception fusion, and lays a solid foundation for the propulsion of vehicle-road collaborative perception fusion.
By now it should be appreciated by those skilled in the art that while exemplary embodiments of the invention have been shown and described in detail herein, many other variations or modifications that are consistent with the principles of the invention may be directly ascertained or derived from the teachings of the present disclosure without departing from the spirit and scope of the invention. Accordingly, the scope of the present invention should be understood and deemed to cover all such other variations or modifications.
Claims (14)
- The vehicle comprises a vehicle-mounted GPS time service unit, a vehicle-mounted NTP server and a plurality of vehicle-mounted sensor data processing units, wherein the vehicle-mounted NTP server is respectively connected with the vehicle-mounted GPS time service unit and a first remote time server, and the vehicle-mounted GPS time service unit is configured to provide a first GPS time service signal for the vehicle-mounted NTP server when a GPS signal is normally acquired; the vehicle-road cooperation system further comprises road side equipment, wherein the road side equipment comprises a vehicle-road cooperation NTP server;the vehicle-road cooperative time synchronization method comprises the following steps:judging whether the vehicle-mounted NTP server receives the first GPS time service signal or not;when the vehicle-mounted NTP server does not receive the first GPS time service signal, NTP level information of the vehicle-mounted NTP server and NTP level information of the first remote time server are read at the same time, and the vehicle-mounted NTP server is synchronized with the lower level of the vehicle-mounted NTP server and the lower level of the vehicle-mounted NTP server;after the synchronization is successful, a first synchronization instruction is sent to each vehicle-mounted sensor data processing unit, so that each vehicle-mounted sensor data processing unit synchronizes the time of the vehicle-mounted NTP server through a network time protocol.
- The vehicle-road cooperative time synchronization method of claim 1, wherein the step of determining whether the vehicle-mounted NTP server receives the first GPS time service signal further comprises:and enabling the vehicle-mounted NTP server to synchronize GPS hardware reference time when the vehicle-mounted NTP server receives the first GPS time service signal.
- The vehicle-road cooperative time synchronization method according to claim 1 or 2, wherein the vehicle-mounted GPS time service unit comprises a combined inertial navigation system and a signal expansion board connected with each other, the signal expansion board is connected with the vehicle-mounted NTP server, and the vehicle further comprises a vehicle-end laser radar connected with the signal expansion board so as to acquire the first GPS time service signal through the signal expansion board;the vehicle-road cooperative time synchronization method further comprises the following steps:judging whether the vehicle-end laser radar receives the first GPS time service signal or not;and enabling the vehicle-end laser radar to synchronize GPS hardware reference time when the vehicle-end laser radar receives the first GPS time service signal.
- The vehicle-road cooperative time synchronization method of claim 3, wherein the step of determining whether the vehicle-side lidar receives the first GPS time service signal further comprises:And enabling the vehicle-end laser radar to synchronize the time of the vehicle-mounted NTP server when the vehicle-end laser radar does not receive the first GPS time service signal.
- The vehicle-road cooperative time synchronization method according to claim 4, wherein the step of synchronizing the vehicle-side lidar with the time of the on-board NTP server when the vehicle-side lidar does not receive the first GPS timing signal comprises:detecting transmission delay when a test node in a local area network where the vehicle-end laser radar is positioned communicates with the vehicle-mounted NTP server, wherein the test node is connected with the vehicle-mounted NTP server through a switch;and determining the local time of the vehicle-end laser radar according to the transmission time delay and the local time of the vehicle-mounted NTP server.
- The vehicle-road cooperative time synchronization method of claim 5, wherein,the step of detecting the transmission delay when the test node in the local area network where the vehicle-end laser radar is located communicates with the vehicle-mounted NTP server comprises the following steps:transmitting a first data packet carrying the first transmission time from the vehicle-mounted NTP server to the test node at the first transmission time, recording a first receiving time when the test node receives the first data packet, and calculating a difference A2B between the first receiving time and the first transmission time;Transmitting a second data packet carrying the second transmission time from the test node to the vehicle-mounted NTP server at the second transmission time, recording a second receiving time when the vehicle-mounted NTP server receives the second data packet, and calculating a difference B2A between the second receiving time and the second transmission time;the clock offset C is calculated according to the following equation (1):C＝(A2B-B2A)/2 (1)；the transmission delay deltat' is calculated according to the following equation (2):ΔT′＝A2B–C (2)。
- the vehicle-road cooperative time synchronization method of claim 5, wherein,the step of determining the local time of the vehicle-end laser radar according to the transmission delay and the local time of the vehicle-mounted NTP server comprises the following steps:a second synchronous instruction is sent to the vehicle-mounted laser radar from the vehicle-mounted NTP server at a third moment, and the second synchronous instruction carries the transmission delay;and setting the local time of the vehicle-mounted laser radar as the sum of the third moment and the transmission delay when the vehicle-mounted laser radar receives the second synchronous command.
- The vehicle-road cooperative time synchronization method according to claim 1, wherein the vehicle-road cooperative NTP server is clocked by a road-side GPS time-supply unit or the second remote time server;When the vehicle-road cooperative NTP server is taught by the road side GPS time service unit, the NTP level of the vehicle-road cooperative NTP server is lower than that of the first remote time server;the step of synchronizing the in-vehicle NTP server with the lower of the two levels includes:and synchronizing the vehicle-mounted NTP server with the vehicle-road cooperative NTP server when the vehicle-road cooperative NTP server is taught by the road side GPS timing unit.
- The road side equipment comprises a road side GPS timing unit, a road cooperation NTP server and a plurality of road side sensor data processing units, wherein each road side sensor data processing unit is connected with the road cooperation NTP server, and the road cooperation NTP server is provided with a second GPS authorization signal by the road side GPS timing unit or is timing by a second remote time server; the vehicle-road cooperation system further comprises a vehicle, the vehicle comprises a vehicle-mounted GPS time service unit and a vehicle-mounted NTP server, the vehicle-mounted GPS time service unit is configured to provide a first GPS time service signal for the vehicle-mounted NTP server when a GPS signal is normally acquired, and the vehicle-mounted NTP server is connected with the vehicle-road cooperation NTP server;The vehicle-road cooperative time synchronization method comprises the following steps:judging whether the vehicle-road cooperative NTP server receives the second GPS time service signal or not;when the vehicle-road cooperative NTP server receives the second GPS time service signal, enabling the vehicle-road cooperative NTP server to synchronize GPS hardware reference time;receiving a synchronization request sent by the vehicle-mounted NTP server, and providing reference time for the vehicle-mounted NTP server for synchronization in response to the synchronization request, wherein the synchronization request is sent by the vehicle-mounted NTP server when the first GPS time service signal is not received and the NTP level of the vehicle-mounted cooperative NTP server is lower than the NTP level of the first remote time server;and sending a third synchronization instruction to each road side sensor data processing unit so that each road side sensor data processing unit synchronizes the time of the vehicle-road cooperative NTP server through a network time protocol.
- The vehicle-road cooperative time synchronization method of claim 9, wherein,when the vehicle-road cooperative NTP server is taught by the road side GPS timing unit, the NTP level of the vehicle-road cooperative NTP server is lower than that of the first remote time server.
- The vehicle-road cooperative time synchronization method according to claim 9, after determining whether the vehicle-road cooperative NTP server receives the second GPS time service signal, further comprising:and synchronizing the time of the second remote time server by the vehicle-road cooperative NTP server when the vehicle-road cooperative NTP server does not receive the second GPS time service signal.
- The first vehicle road cooperation time synchronization device is applied to a vehicle of a vehicle road cooperation system and comprises a vehicle-mounted GPS time service unit, a vehicle-mounted NTP server, a plurality of vehicle-mounted sensor data processing units, a memory and a processor, wherein the vehicle-mounted NTP server is respectively connected with the vehicle-mounted GPS time service unit and a first remote time server, and a control program is stored in the memory and is used for realizing the vehicle road cooperation time synchronization method according to any one of claims 1-8 when being executed by the processor.
- A second vehicle road cooperation time synchronization device applied to road side equipment of a vehicle road cooperation system, the vehicle road cooperation time synchronization device comprises a road side GPS time service unit, a vehicle road cooperation NTP server, a plurality of road side sensor data processing units, a memory and a processor, each road side sensor data processing unit is connected with the vehicle road cooperation NTP server, the vehicle road cooperation NTP server is provided with a second GPS authorization signal by the road side GPS time service unit or is time-service by a second remote time server, and a control program is stored in the memory, and when being executed by the processor, the control program is used for realizing the vehicle road cooperation time synchronization method according to any one of claims 9-11.
- A vehicle road cooperative time synchronization system comprising the first vehicle road cooperative time synchronization device of claim 12 and the second vehicle road cooperative time synchronization device of claim 13.
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