CN112383675B - Time synchronization method and device and terminal equipment - Google Patents
Time synchronization method and device and terminal equipment Download PDFInfo
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Abstract
The invention discloses a time synchronization method, a device and terminal equipment, wherein the method comprises the following steps: the POS positioning and orientation system obtains GPS time service data output by a GPS and sends the GPS time service data to the airborne computer, and then the airborne computer receives and analyzes the GPS time service data to obtain a time signal and a pulse per second signal output by the GPS; and then introducing the time signal and the second pulse signal into a synchronous controller, and synchronizing the synchronous controller to obtain time synchronous data. According to the invention, the synchronous recording of the data of each sensor is realized through the time service type GPS, the second pulse signal and the synchronous controller, the synchronous data acquisition is completed while the time reference is determined with high precision, the task load of the onboard industrial control computer is reduced, and the robustness of the system is ensured.
Description
Technical Field
The present invention relates to the field of time synchronization technologies, and in particular, to a time synchronization method, apparatus, and terminal device.
Background
The sensors are often utilized to conduct intelligent inspection in the power system, but time precision of the sensors is not uniform, and errors are easy to generate. The traditional multi-sensor independent control data acquisition method is very few in application, and particularly, the unification of time and space references of multi-sensor data acquisition is realized. For example, the existing time synchronization methods, such as chinese patent publication number CN110599570a and publication date 2019.12.20, are a map generation method and system based on crowdsourcing data open scene, which performs time synchronization on the extracted semantic information and gps track information through ID and timestamp of the vehicle. However, such methods are equally unsuitable for multi-data source systems consisting of uv cameras, laser scanners, visible light cameras, thermal infrared imagers, which do not guarantee that the individual multi-data source systems establish high precision and uniform time synchronization.
Disclosure of Invention
The invention provides a time synchronization method, a time synchronization device and terminal equipment. The invention is suitable for multiple data source systems consisting of an ultraviolet camera, a laser scanner, a visible light camera, a thermal infrared imager and the like, and ensures that each multiple data source system establishes high precision and uniform time synchronization.
The specific technical scheme is as follows:
a method of time synchronization, comprising:
the POS positioning and orientation system obtains GPS time service data output by a GPS and sends the GPS time service data to the airborne computer, and then the airborne computer receives and analyzes the GPS time service data to obtain a time signal and a pulse per second signal output by the GPS; then introducing the time signal and the second pulse signal into a synchronous controller, and synchronizing the synchronous controller to obtain time synchronous data; wherein, the second pulse signal is PPS signal; the time synchronization data comprises time information and a corresponding second pulse signal;
the synchronous controller simultaneously sends time synchronization data after time service to the ultraviolet camera, the laser scanner, the visible light camera and the thermal infrared imager; meanwhile, the ultraviolet camera, the laser scanner, the visible light camera and the thermal infrared imager respectively clear the second count after receiving the second pulse signal;
triggering the ultraviolet camera by the synchronous controller in a hard triggering mode, sending the exposure time of the ultraviolet camera to an onboard computer for recording, and taking the exposure time in the acquired image information as an initial exposure time so as to conveniently and sequentially identify the time of the image information shot by the ultraviolet camera; the synchronous controller simultaneously utilizes an API interface to trigger the exposure time of the visible light camera in a soft triggering mode, so that the exposure time which is the same as that of the ultraviolet camera is obtained, and the exposure time is taken as the initial exposure time, so that the image information shot by the visible light camera can be identified in time later;
after the time references are unified, a high-frequency is preset in the POS positioning and orientation system, the spatial position and posture data corresponding to the acquisition time of each frame of data in the original data acquired by the multi-data source system consisting of the ultraviolet camera, the laser scanner, the visible light camera and the thermal infrared imager are acquired, and then the unified operation of spatial reference calibration of each frame of data of the multi-data source system is realized by a reference object.
Preferably, as an embodiment; the airborne computer comprises a GPS time service receiving module, and the time service receiving module is a GPS time service receiver.
Preferably, as an embodiment; the preset high-frequency range of the POS positioning and orientation system is 100-200 Hz.
Preferably, as an embodiment; before the synchronous controller simultaneously sends time synchronization data after time service to the ultraviolet camera, the laser scanner, the visible light camera and the thermal infrared imager, further time calibration early warning operation is implemented on time information in the current time synchronization data by using Beidou satellite time service signals through a ground assistance system.
Preferably, as an embodiment; the ground assistance system utilizes Beidou satellite time service signals to implement further time calibration early warning operation on time information in the current time synchronization data, and the method specifically comprises the following operation steps:
the ground assistance system receives a downlink signal from a Beidou satellite time service through a Beidou satellite time service antenna, obtains an asynchronous serial code stream signal, completes a time stamp generation process for the asynchronous serial code stream signal, and then analyzes time information in the time stamp to be used as reference time information for calibration;
transmitting the reference time information to a synchronous controller;
the synchronous controller performs time value subtraction on the reference time information and the time information recorded by the time synchronous data to obtain a time delay measured value; and judging the relation between the time delay measured value and a preset standard time delay measured value, and if the time delay measured value is larger than the standard time delay measured value, judging that the time information error in the current time synchronization data exceeds the limit, and prompting early warning information.
Preferably, as an embodiment; after the ultraviolet camera, the laser scanner, the visible light camera and the thermal infrared imager respectively receive the second pulse signals, resetting the second count, so as to obtain time information accurate to mu s, and simultaneously the ultraviolet camera and the visible light camera also receive local clock signals from a ground assistance system as detection frame pulse signals, so that the remote calibration operation steps of the local clock are realized; wherein the ground assistance system comprises a ground assistance server.
Preferably, as an embodiment; the steps of remotely calibrating the local clock are as follows:
receiving a GPS pulse-per-second signal, and performing frequency multiplication operation on the GPS pulse-per-second signal according to a signal frame period to generate a frame synchronization sequence signal to be detected;
receiving a local clock signal from a ground assistance system as a preliminary detection frame pulse signal;
performing frequency multiplication operation on the prepared detection frame pulse signals to generate detection frame pulse signals;
obtaining clock deviation between a local clock signal and a GPS second pulse signal according to deviation between a clock analyzed by a frame synchronization sequence signal to be detected and a clock analyzed by a detection frame pulse signal;
the local clock is calibrated according to the clock bias.
Preferably, as an embodiment; the synchronous controller triggers the ultraviolet camera in a hard triggering mode, and specifically comprises the following operation steps:
the ultraviolet camera receives the hard trigger of the synchronous controller, and then the ultraviolet camera sends a Strobe signal to the synchronous controller;
the synchronous controller simultaneously utilizes an API interface to trigger the exposure time of the visible light camera in a soft triggering mode so as to obtain the exposure time same as that of the ultraviolet camera, and the method specifically comprises the following operation steps:
the synchronous controller analyzes the time moment in the Strobe signal of the external trigger signal, obtains the time difference between the emission and the exposure of the Strobe signal of the ultraviolet camera, and obtains the first exposure moment of the ultraviolet camera by utilizing the time moment in the Strobe signal of the external trigger signal plus the time difference between the emission and the exposure of the Strobe signal; wherein the time difference between the emission and exposure of the Strobe signal is the first time difference belonging to the ultraviolet camera;
and directly calling a second time difference from the soft triggering time of the visible light camera to the exposure time by using an API interface of the synchronous controller, so as to calculate the soft triggering time required by the soft triggering of the ultraviolet camera, and sending the soft triggering time to the visible light camera for soft triggering by using the API interface of the synchronous controller after the synchronous controller detects the time when the current time reaches the soft triggering time, thereby ensuring that the visible light camera is exposed at the first exposure time after the soft triggering.
Correspondingly, the invention also provides a time synchronization device which comprises a POS positioning and orientation system, an onboard computer and a synchronization controller, wherein the POS positioning and orientation system comprises a GPS; the POS positioning and orientation system is electrically connected with the onboard computer, and the onboard computer is also electrically connected with the synchronous controller; the synchronous controller is electrically connected with the ultraviolet camera, the laser scanner, the visible light camera and the thermal infrared imager at the same time.
The invention also provides a terminal device, comprising: a processor and a memory, the memory storing a computer program, the processor being configured to execute the computer program to implement the multi-sensor based time synchronization method described above.
The technical scheme of the invention has the following beneficial effects:
the time synchronization method based on the multisensor is different from the traditional data acquisition method controlled independently by the multisensor, the time and the space reference of the multisensor data acquisition can be unified by the multisensor synchronization control method provided by the design of the invention, and each data frame of the acquired laser point cloud data, optical image data, infrared video data and ultraviolet image data is synchronous observation data, so that a data basis is laid for realizing fault diagnosis of multisource data comparison analysis. According to the invention, the synchronous recording of the data of each sensor is realized through the time service type GPS, the second pulse signal and the synchronous controller, the synchronous data acquisition is completed while the time reference is determined with high precision, the task load of the onboard industrial control computer is reduced, and the robustness of the system is ensured.
The invention realizes high-precision synchronous triggering by combining the improved camera triggering mode with the second pulse signal, and ensures the subsequent execution effect of time synchronization.
Drawings
FIG. 1 is a flow chart of a time synchronization method of the present invention;
FIG. 2 is a flow chart of a further time alignment early warning operation performed on time information in the current time synchronization data;
FIG. 3 is a flowchart illustrating the operation steps of remotely calibrating a local clock;
FIG. 4 is a schematic diagram of a process for hard triggering an ultraviolet camera and soft triggering a visible light camera according to the present invention;
fig. 5 is a schematic structural diagram of a time synchronization device according to the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments.
The components of the embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the invention, as presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be made by a person skilled in the art without making any inventive effort, are intended to be within the scope of the present invention.
The terms "comprises," "comprising," "including," or any other variation thereof, are intended to cover a specific feature, number, step, operation, element, component, or combination of the foregoing, which may be used in various embodiments of the present invention, and are not intended to first exclude the presence of or increase the likelihood of one or more other features, numbers, steps, operations, elements, components, or combinations of the foregoing.
Furthermore, the terms "first," "second," "third," and the like are used merely to distinguish between descriptions and should not be construed as indicating or implying relative importance.
Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which various embodiments of the invention belong. The terms (such as those defined in commonly used dictionaries) will be interpreted as having a meaning that is the same as the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein in connection with the various embodiments of the invention.
Example 1
The embodiment provides a time synchronization method which can be applied to an application platform of an unmanned aerial vehicle.
The unmanned aerial vehicle multi-sensor data acquisition system used in the embodiment can acquire massive high-precision airborne laser scanning (light detection and ranging, li DAR) point cloud data of a power line corridor, high-resolution aviation digital images, thermal infrared images, ultraviolet images and the like. The data acquisition system mainly comprises an ultraviolet camera, a laser scanner, a visible light camera, a thermal infrared imager, a receiver, a global positioning system (global positioning system, GPS), a POS positioning and orientation system (position and orientation system, POS), a flight planning and management system, a data storage system and the like.
The ultraviolet camera, the laser scanner, the visible light camera and the infrared thermal imager are respectively associated with the POS positioning and orientation system, so that the time coordinates of the ultraviolet camera, the laser scanner, the visible light camera and the infrared thermal imager on the machine are unified, and the unification of the data time and the space reference acquired by each sensor is realized.
As shown in fig. 1, a time synchronization method includes the following operation procedures:
the POS positioning and orientation system obtains GPS time service data output by a GPS and sends the GPS time service data to the airborne computer, and then the airborne computer receives and analyzes the GPS time service data to obtain a time signal and a pulse per second signal output by the GPS; then introducing the time signal and the second pulse signal into a synchronous controller, and synchronizing the synchronous controller to obtain time synchronous data; wherein, pulse Per Second (PPS) signal is PPS signal; the time synchronization data comprises time information and a corresponding second pulse signal;
the synchronous controller simultaneously sends time synchronization data after time service to the ultraviolet camera, the laser scanner, the visible light camera and the thermal infrared imager; meanwhile, the ultraviolet camera, the laser scanner, the visible light camera and the thermal infrared imager respectively clear the second count after receiving the second pulse signal;
triggering the ultraviolet camera by the synchronous controller in a hard triggering mode, sending the exposure time of the ultraviolet camera to an onboard computer for recording, and taking the exposure time in the acquired image information as an initial exposure time so as to conveniently and sequentially identify the time of the image information shot by the ultraviolet camera; the synchronous controller simultaneously utilizes an API interface to trigger the exposure time of the visible light camera in a soft triggering mode, so that the exposure time which is the same as that of the ultraviolet camera is obtained, and the exposure time is taken as the initial exposure time, so that the image information shot by the visible light camera can be identified in time later; by the operation, the time of the POS positioning and orientation system, the visible light camera, the laser scanner, the thermal infrared imager and the ultraviolet camera is uniform GPS time, and the aim of unifying time references of multiple data sources is fulfilled.
After the time references are unified, presetting a high-frequency in a POS positioning and orientation system, acquiring spatial position and posture data corresponding to the acquisition time of each frame of data in the original data acquired by a multi-data source system consisting of an ultraviolet camera, a laser scanner, a visible light camera and an infrared thermal imager, and then realizing the spatial reference calibration unified operation of each frame of data of the multi-data source system by a reference object; the spatial position and posture data corresponding to each frame data acquisition moment of each sensor can be obtained from the original data recorded by high frequency (100-200 Hz), and the unification of the spatial references is completed.
Because the mu s or ns time cannot be recorded with high precision by using a computer high-level language programming program, the synchronous recording of the data of each sensor is realized through the time service type GPS and the synchronous controller, the synchronous data acquisition is completed while the time reference is determined with high precision, the task load of an onboard industrial control computer is reduced, and the robustness of the system is ensured.
In addition, the POS positioning and orientation system provided by the invention is a time-frequency server with high precision and high precision frequency, which is developed and designed, adopts standard 2U design, and can externally output a plurality of time-frequency signals such as PTP, NTP, IRIG-B code, 1PPS, 10MHz frequency standard and the like, and a receiver and a rubidium clock (constant temperature crystal oscillator) are adopted. And a disciplined frequency mechanism supporting a rubidium clock and crystal oscillator mixed mode is provided. The POS positioning and orientation system is a comprehensive frequency source with high precision time keeping, high performance stability and low phase noise. The POS positioning and orientation system is internally provided with a mixed time keeping strategy of a rubidium clock and a bottom phase noise constant temperature crystal oscillator. The signal has the advantages of good long-term stability, no accumulated error, high time synchronism with the international standard, low phase noise and better stability.
In this embodiment, the airborne computer includes a GPS timing receiving module, the timing receiving module is a GPS timing receiver, and the preset high-frequency range of the POS positioning and orientation system is 100-200 Hz.
In this embodiment, before the synchronization controller simultaneously sends time synchronization data after time service to the ultraviolet camera, the laser scanner, the visible light camera and the thermal infrared imager, a ground assistance system uses Beidou satellite time service signals to implement further time calibration early warning operation on time information in the current time synchronization data.
As shown in fig. 2, by using the Beidou satellite time service signal through the ground assistance system, further time calibration early warning operation is implemented on time information in the current time synchronization data, and specifically the method comprises the following operation steps:
the ground assistance system receives a downlink signal from a Beidou satellite time service through a Beidou satellite time service antenna, obtains an asynchronous serial code stream signal, completes a time stamp generation process for the asynchronous serial code stream signal, and then analyzes time information in the time stamp to be used as reference time information for calibration;
transmitting the reference time information to a synchronous controller;
the synchronous controller performs time value subtraction on the reference time information and the time information recorded by the time synchronous data to obtain a time delay measured value; and judging the relation between the time delay measured value and a preset standard time delay measured value, and if the time delay measured value is larger than the standard time delay measured value, judging that the time information error in the current time synchronization data exceeds the limit, and prompting the early warning information.
In the embodiment, after the ultraviolet camera, the laser scanner, the visible light camera and the thermal infrared imager respectively receive the second pulse signals, the second count is cleared, so that time information accurate to mu s is obtained, and meanwhile, the ultraviolet camera and the visible light camera also receive local clock signals from a ground assistance system as detection frame pulse signals, so that the remote calibration operation steps of the local clock are realized; the ground assistance system ground comprises a ground assistance server.
As shown in fig. 3, the operation steps of remotely calibrating the local clock are as follows:
receiving a GPS pulse-per-second signal, and performing frequency multiplication operation on the GPS pulse-per-second signal according to a signal frame period to generate a frame synchronization sequence signal to be detected;
receiving a local clock signal from a ground assistance system as a preliminary detection frame pulse signal;
performing frequency multiplication operation on the prepared detection frame pulse signals to generate detection frame pulse signals;
obtaining clock deviation between a local clock signal and a GPS second pulse signal according to deviation between a clock analyzed by a frame synchronization sequence signal to be detected and a clock analyzed by a detection frame pulse signal;
the local clock is calibrated according to the clock bias.
It should be noted that, the invention can generate the frame synchronization sequence signal to be detected after multiplying power operation by multiplying power of GPS second pulse signal by frequency multiplication clock; meanwhile, receiving a local clock signal from a ground assistance system as a preliminary detection frame pulse signal, performing multiplying power processing as well, and obtaining clock deviation between a server local clock signal and a GPS second pulse signal according to deviation between a clock analyzed by a frame synchronization sequence signal to be detected and a clock analyzed by the detection frame pulse signal; and finally, the local clock can be calibrated rapidly according to clock deviation.
As shown in fig. 4, the synchronous controller triggers the ultraviolet camera by a hard triggering mode, and specifically includes the following operation steps:
the ultraviolet camera receives the hard trigger of the synchronous controller, and then the ultraviolet camera sends a Strobe signal to the synchronous controller;
the synchronous controller simultaneously utilizes an API interface to trigger the exposure time of the visible light camera in a soft triggering mode so as to obtain the exposure time same as that of the ultraviolet camera, and the method specifically comprises the following operation steps:
the synchronous controller analyzes the time moment in the Strobe signal of the external trigger signal, obtains the time difference between the emission and the exposure of the Strobe signal of the ultraviolet camera, and can obtain the first exposure moment of the ultraviolet camera by utilizing the time moment in the Strobe signal of the external trigger signal plus the time difference between the emission and the exposure of the Strobe signal; wherein the time difference between the emission and exposure of the Strobe signal is the first time difference belonging to the ultraviolet camera;
and directly calling a second time difference from the soft triggering time of the visible light camera to the exposure time by using an API interface of the synchronous controller, so as to calculate the soft triggering time required by the soft triggering of the ultraviolet camera, and sending the soft triggering time to the visible light camera for soft triggering by using the API interface of the synchronous controller after the synchronous controller detects the time when the current time reaches the soft triggering time, thereby ensuring that the visible light camera is exposed at the first exposure time after the soft triggering.
It should be noted that the existing problems at present are: even if the plurality of cameras receive calibrated high-precision second pulse signals, time synchronization of the plurality of cameras with higher precision requirements cannot be ensured, which is because: the synchronous triggering of the higher precision time of the cameras is too high for hardware, the cost of the cameras is higher, and the time precision is difficult to guarantee due to the synchronous hard triggering; the method is implemented by adopting a mode of ultraviolet camera hard triggering and visible light camera soft triggering; the ultraviolet camera receives direct hard triggering operation of the synchronous controller;
wherein the trigger belongs to an external trigger mode: the camera collects images through signals given by the outside, and the external trigger signals can be software signals or hardware signals; if a hard triggering mode is adopted, a pulse signal can be generated by using one MCU in the synchronous controller to carry out hard triggering on the sensor devices of the two cameras, but the mode has higher cost and low synchronous triggering precision. However, in this embodiment, the triggering of the two cameras is a soft-hard combined triggering method, and the soft-hard combined triggering method is also numerous. The ultraviolet camera receives the hard trigger of the synchronous controller, then the ultraviolet camera sends an external trigger signal (Strobe signal) to the synchronous controller, the synchronous controller analyzes the time moment in the Strobe signal of the external trigger signal, and the exposure moment (namely, the first exposure moment) of the accurate ultraviolet camera is calculated; it should be noted that the camera trigger output signal is a switch signal, and can be used to control other external devices such as a camera and a controller. The camera receives the trigger to expose, and when the exposure of the camera occurs, a Strobe signal is output, and the signal is active high. The signal can be used as a data source to assist in soft triggering of other cameras; the Strobe signal is asserted earlier than the exposure time. The working principle is that the first exposure time (namely the exposure time) of the ultraviolet camera is calculated by the synchronous controller by utilizing the function, namely, the time moment in the external trigger signal Strobe signal is analyzed and the time difference between the emission and the exposure of the Strobe signal is added (the time difference between the emission and the exposure of the Strobe signal can be defined as the first time difference), and the research shows that the time difference between the emission and the exposure of the Strobe signal is a fixed value through research and verification, and the value of the time difference is related to the hardware information of the camera, so that the first exposure time of the ultraviolet camera can be obtained by calculating the time moment in the external trigger signal Strobe signal and the time difference between the emission and the exposure of the Strobe signal after the hardware model of the ultraviolet camera is determined.
Then, the API interface of the synchronous controller is utilized to directly call a second time difference (the second time difference is also a fixed value after the visible light camera is determined and the software application is determined) from the soft triggering time of the visible light camera to the first exposure time, so that the soft triggering time required by the ultraviolet camera to be soft triggered can be calculated, after the API waiting time of the synchronous controller reaches the time of the soft triggering time, the API of the synchronous controller sends the soft triggering time to the visible light camera to carry out soft triggering, and thus the exposure can be accurately realized at a certain time after the visible light camera carries out soft triggering (namely, the exposure of the visible light camera at the first exposure time is ensured).
In summary, unlike the traditional multi-sensor independent control data acquisition method, the multi-sensor time synchronization control method provided by the embodiment of the invention can realize unification of time and space references of multi-sensor data acquisition, and each data frame of the acquired laser point cloud data, optical image data, infrared video data and ultraviolet image data is synchronous observation data, thereby laying a data foundation for realizing fault diagnosis of multi-source data comparison analysis; and finally, the camera triggering mode is utilized to realize high-precision synchronous triggering, so that the subsequent execution effect of time synchronization is ensured.
Example 2
As shown in fig. 5, based on the method of the foregoing embodiment 1, this embodiment proposes a time synchronization device, including: the system comprises a POS positioning and orientation system, an onboard computer and a synchronous controller, wherein the POS positioning and orientation system comprises a GPS; the POS positioning and orientation system is electrically connected with the onboard computer, and the onboard computer is also electrically connected with the synchronous controller; the synchronous controller is electrically connected with the ultraviolet camera, the laser scanner, the visible light camera and the thermal infrared imager at the same time.
In this embodiment, the system further comprises a ground assistance system, and the ground assistance system is electrically connected with the synchronous controller.
It can be understood that the multi-sensor-based time synchronization device described above corresponds to the on-screen display method of the multi-operating system of embodiment 1. Any of the alternatives in embodiment 1 are also applicable to this embodiment and will not be described in detail here.
Example 3
The invention also provides a terminal device, comprising: a processor and a memory, the memory storing a computer program for executing the computer program to implement the multi-sensor based time synchronization method of embodiment 1 described above.
The memory may include a program storage area and a data storage area, wherein the program storage area may store an operating system, at least one application program required for a function; the storage data area may store data created according to the use of the terminal, etc. In addition, the memory may include high-speed random access memory, and may also include non-volatile memory, such as at least one magnetic disk storage device, flash memory device, or other volatile solid-state storage device.
The present invention also provides a computer readable storage medium storing the computer program for use in the above terminal.
In the several embodiments provided in this application, it should be understood that the disclosed apparatus and method may be implemented in other manners as well. The apparatus embodiments described above are merely illustrative, for example, of the flow diagrams and block diagrams in the figures, which illustrate the architecture, functionality, and operation of possible implementations of apparatus, methods and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems which perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.
The foregoing is merely illustrative of the present invention, and the present invention is not limited thereto, and any person skilled in the art will readily recognize that variations or substitutions are within the scope of the present invention.
Claims (9)
1. A method of time synchronization, comprising:
the POS positioning and orientation system obtains GPS time service data output by a GPS and sends the GPS time service data to the airborne computer, and then the airborne computer receives and analyzes the GPS time service data to obtain a time signal and a pulse per second signal output by the GPS; then introducing the time signal and the second pulse signal into a synchronous controller, and synchronizing the synchronous controller to obtain time synchronous data; wherein, the second pulse signal is PPS signal; the time synchronization data comprises time information and a corresponding second pulse signal;
the synchronous controller simultaneously sends time synchronization data after time service to the ultraviolet camera, the laser scanner, the visible light camera and the thermal infrared imager; meanwhile, the ultraviolet camera, the laser scanner, the visible light camera and the thermal infrared imager respectively clear the second count after receiving the second pulse signal;
triggering the ultraviolet camera by the synchronous controller in a hard triggering mode, sending the exposure time of the ultraviolet camera to an onboard computer for recording, and taking the exposure time in the acquired image information as an initial exposure time for carrying out time identification on the image information shot by the ultraviolet camera subsequently; the synchronous controller simultaneously utilizes an API interface to trigger the exposure time of the visible light camera in a soft triggering mode, so as to obtain the exposure time which is the same as that of the ultraviolet camera and take the exposure time as the initial exposure time for carrying out subsequent time identification on the image information shot by the visible light camera;
after the time references are unified, a high-frequency is preset in the POS positioning and orientation system, the spatial position and posture data corresponding to the acquisition time of each frame of data in the original data acquired by the multi-data source system consisting of an ultraviolet camera, a laser scanner, a visible light camera and an infrared thermal imager are acquired, and then the spatial reference calibration unified operation of each frame of data of the multi-data source system is realized by a reference object.
2. The method of claim 1, wherein the on-board computer includes a GPS timing receiver module, the timing receiver module being a GPS timing receiver.
3. The time synchronization method according to claim 1, wherein the preset high frequency range of the POS positioning and orienting system is 100 to 200Hz.
4. The time synchronization method according to claim 1, wherein before the synchronization controller simultaneously transmits time synchronization data after time service to the ultraviolet camera, the laser scanner, the visible light camera and the thermal infrared imager, further time calibration early warning operation is performed on time information in the current time synchronization data by using a Beidou satellite time service signal through a ground assistance system.
5. The time synchronization method according to claim 4, wherein the ground assistance system uses Beidou satellite timing signals to perform further time calibration early warning operation on time information in the current time synchronization data, and the method specifically comprises the following operation steps:
the ground assistance system receives a downlink signal from a Beidou satellite time service through a Beidou satellite time service antenna, obtains an asynchronous serial code stream signal, completes a time stamp generation process for the asynchronous serial code stream signal, and then analyzes time information in the time stamp to be used as reference time information for calibration;
transmitting the reference time information to a synchronous controller;
the synchronous controller performs time value subtraction on the reference time information and the time information recorded by the time synchronous data to obtain a time delay measured value; and judging the relation between the time delay measured value and a preset standard time delay measured value, and if the time delay measured value is larger than the standard time delay measured value, judging that the time information error in the current time synchronization data exceeds the limit, and prompting early warning information.
6. The time synchronization method according to claim 5, wherein after the ultraviolet camera, the laser scanner, the visible light camera and the thermal infrared imager respectively receive the second pulse signals, the second count is cleared to obtain time information accurate to μs, and the ultraviolet camera and the visible light camera also receive local clock signals from the ground assistance system as detection frame pulse signals, so that the calibration operation step of the local clock is remotely performed; wherein the ground assistance system comprises a ground assistance server.
7. The method of time synchronization according to claim 6, wherein the step of remotely calibrating the local clock comprises the steps of:
receiving a GPS pulse-per-second signal, and performing frequency multiplication operation on the GPS pulse-per-second signal according to a signal frame period to generate a frame synchronization sequence signal to be detected;
receiving a local clock signal from a ground assistance system as a preliminary detection frame pulse signal;
performing frequency multiplication operation on the prepared detection frame pulse signals to generate detection frame pulse signals;
obtaining clock deviation between a local clock signal and a GPS second pulse signal according to deviation between a clock analyzed by a frame synchronization sequence signal to be detected and a clock analyzed by a detection frame pulse signal;
the local clock is calibrated according to the clock bias.
8. The time synchronization method according to claim 1, wherein the synchronization controller triggers the ultraviolet camera by a hard triggering manner, and specifically comprises the following operation steps:
the ultraviolet camera receives the hard trigger of the synchronous controller, and then the ultraviolet camera sends a Strobe signal to the synchronous controller;
the synchronous controller simultaneously utilizes an API interface to trigger the exposure time of the visible light camera in a soft triggering mode so as to obtain the exposure time same as that of the ultraviolet camera, and the method specifically comprises the following operation steps:
the synchronous controller analyzes the time moment in the Strobe signal of the external trigger signal, obtains the time difference between the emission and the exposure of the Strobe signal of the ultraviolet camera, and obtains the first exposure moment of the ultraviolet camera by utilizing the time moment in the Strobe signal of the external trigger signal plus the time difference between the emission and the exposure of the Strobe signal; wherein the time difference between the emission and exposure of the Strobe signal is the first time difference belonging to the ultraviolet camera;
and directly calling a second time difference from the soft triggering time of the visible light camera to the exposure time by using an API interface of the synchronous controller, so as to calculate the soft triggering time required by the soft triggering of the ultraviolet camera, and sending the soft triggering time to the visible light camera for soft triggering by using the API interface of the synchronous controller after the synchronous controller detects the time when the current time reaches the soft triggering time, thereby ensuring that the visible light camera is exposed at the first exposure time after the soft triggering.
9. A terminal device, comprising: a processor and a memory, the memory storing a computer program for executing the computer program to implement the time synchronization method according to any one of claims 1 to 8.
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| CN113176591A (en) * | 2021-05-19 | 2021-07-27 | 浙江宇视科技有限公司 | Time synchronization method and device of monitoring platform, electronic equipment and storage medium |
| CN114220255A (en) * | 2021-12-29 | 2022-03-22 | 宜昌测试技术研究所 | Distributed acoustic equipment synchronous control system and method |
| CN114812673B (en) * | 2022-04-02 | 2023-11-10 | 北京卫星环境工程研究所 | Multi-parameter multi-module optical fiber data synchronous test method |
| CN114755693B (en) * | 2022-06-15 | 2022-09-16 | 天津大学四川创新研究院 | Infrastructure facility measuring system and method based on multi-rotor unmanned aerial vehicle |
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