TWI795875B - System and method for grouping results of asynchronous identification of car feature information - Google Patents

Abstract

A system and a corresponding method for grouping results of asynchronous identification of car feature information are provided. The method includes: sensing a car entering a lane; outputting a trigger signal upon sensing the car; identifying a plurality of feature information of the car in response to the trigger signal; outputting an identification result of each feature information, wherein the identification result includes a trigger time that is the current system time of an identification device of the feature information recorded when the identification device receives the trigger signal; and grouping identification results output by the identification devices with the same trigger time into an identification feature record group belonging to the same passage of the same car.

Description

System and method for asynchronous identification result matching of vehicle feature information

The present invention relates to a pairing technology for identifying multiple characteristic information of vehicles in progress, and performing time synchronization by identifying a single trigger signal of a lane. In particular, it is a pairing technology applied in a high-speed, high-density traffic environment, based on a single trigger signal. A system and method for matching asynchronous identification results of multiple vehicle feature information.

It is known that when performing vehicle identification operations, if there are two or more types of feature identification information that need to be paired, multiple lane time synchronization trigger devices are usually used, such as geomagnetic induction at the start point and end point of the identification area The coil records the start and end of the single-vehicle identification time. The feature recognition information results output by different recognition devices within the recognition time range will be paired as feature recognition information belonging to the same vehicle. However, this pairing technology must ensure that no feature recognition information from different vehicles is output within the same recognition time range, so that the pairing can be completed correctly. It is generally suitable for applications in the parking and waiting control single-recognition lane environment, such as toll parking lot recognition gateway. However, when this known technology is applied to a high-speed, high-density free traffic environment, due to excessive changes in vehicle speed, vehicle length, vehicle distance, and vehicle traffic density, and it is impossible to restrict a single vehicle at a time through traffic control equipment, it will lead to problems in practice. identify the same Within the recognition time range, feature recognition information from different vehicles may often appear, resulting in a large rate of feature recognition information pairing errors. Therefore prior art is not applicable to the environment of high-speed free traffic flow.

Another known technology is the Electronic Toll Collection (ETC) system for highways, which is a third-party electronic tag (eTag) identification technology, which is triggered by high-precision laser ranging equipment to capture images of the front of the vehicle and For license plate recognition, the vehicle feature recognition information of the two systems uses the pre-established database of license plate and electronic tag pairing to perform feature recognition information pairing. However, since this known technology is limited to the specific application of expressway charging for which the feature identification information is an established electronic tag pairing database, and cannot be directly applied to other matching applications of vehicle identification information, this prior art technology is not suitable for other applications directly. The application of multiple identification information vehicle identification.

Another conventional technique is to use different feature information identification devices to identify output times of identification results. If the output time of the identification results falls within the specified time error range, it is directly regarded as the same vehicle source as a pair. When this conventional technology is applied to an environment where the density of traffic vehicles increases or the speed of vehicles increases, as the time interval between different vehicles shortens, the proportion of vehicle feature recognition information being incorrectly matched will increase rapidly, so it is only suitable for applications An environment with low traffic density and low speed.

It can be seen that the above-mentioned customary method still has many deficiencies, which is not a good design and needs to be improved urgently.

The invention innovatively proposes to use a single vehicle inductive trigger device in a lane, and when a single vehicle passes, a single trigger signal is used to simultaneously notify all the feature information identification devices of the lane to mark the device system time. Even though the identification results output by various identification devices are very different due to the large difference in identification time requirements, resulting in a time gap in the asynchronous output of the identification results, the same trigger time in different identification results can still be used. Synchronize the information between annotations, and then confirm the feature recognition information belonging to the same train. Therefore, the pairing system and method of the present invention can support the synchronization requirement of high time accuracy required for the recognition results in the environment of high traffic density and high-speed traffic flow.

Compared with the traditional conventional technology, the pairing system and method of the present invention can reduce the pairing error rate by more than 50% under the premise of not needing to establish a known pairing database in advance, and can also effectively eliminate the need for traditional Knowledge technology must obtain the license plate and electronic tag pairing information in advance, related to personal data, laws or related issues.

The present invention proposes a pairing system for asynchronous identification results of multiple feature information of a vehicle based on a single trigger signal time notation, including: defining a set of multiple feature information identification devices for identifying multiple feature information of vehicles; defining a vehicle induction trigger device, It is used to sense the vehicle entering the lane and output the trigger signal synchronously; define an equipment time correction system to provide all lane equipment for system time synchronization; define a vehicle feature identification information pairing equipment to receive the output of various feature information identification equipment of the lane The identification results of the vehicle feature information, and the integration and matching of the feature information identification results from different feature information identification devices but belonging to the same vehicle number.

The present invention also proposes an asynchronous identification method for multiple vehicle feature information based on a single trigger signal time stamp, including: when a vehicle enters the identification lane and triggers a single vehicle sensing trigger device in the lane, the trigger device synchronously transmits the trigger signal to the All feature information identification devices in the lane; when all feature information identification devices receive a trigger signal, they record their own identification device system time, and after completing the identification operation, each asynchronously outputs the identification results of the current vehicle feature information to the identification information pairing device, output the trigger time together.

The present invention further proposes a method for matching the asynchronous identification results of multiple vehicle feature information based on a single trigger signal time annotation, including: when the vehicle enters the identification lane, the multiple feature information identification devices on the lane complete the identification in an asynchronous manner and output the identification Results; vehicle feature recognition data After receiving the recognition results at different time points, the pairing device will pair the recognition results with the same trigger time as the characteristics of the same vehicle through the common trigger signal time stamp in all the recognition results; the pairing device according to the recognition information The trigger time among different identification information is synchronously integrated and compared.

In the asynchronous identification result matching system of vehicle characteristic information mentioned above, the vehicle characteristic information recognized by the plural characteristic information identification equipment includes but not limited to: license plate number, vehicle weight, vehicle speed, number of axles, vehicle model, and electronic tags and other vehicle characteristics.

In the asynchronous identification result matching system of the aforementioned vehicle characteristic information, the detection and triggering methods adopted by the vehicle induction triggering device include but are not limited to: geomagnetic induction coil, laser ranging, infrared blocking, radar ranging, and ultrasonic Trigger methods such as distance measurement.

The asynchronous identification result matching system of vehicle characteristic information mentioned above also includes identification lane attachment facilities, such as the lane sensing gate frame or the space under the ground of the lane, etc., so that the characteristic information identification equipment can be installed or buried thereon.

In another aspect, the present invention proposes a system for pairing asynchronous identification results of vehicle characteristic information, including: a vehicle sensing trigger device for sensing a vehicle entering a lane, and outputting a trigger signal when the vehicle is detected; plural characteristic information The identification device is used to identify the plurality of feature information of the vehicle in response to the trigger signal, and output the identification result of each of the feature information identification devices, wherein the identification result includes a trigger time for sensing entry into the lane, and the trigger time is the The current system time of the feature information recognition device when the feature information recognition device receives the trigger signal; and the feature information pairing device, used to match the same trigger time of the same lane in the identification results output by these feature information recognition devices The pairing is the identification feature record group belonging to the same train number.

In another aspect, the present invention further proposes a method for pairing asynchronous identification results of vehicle characteristic information, including: sensing a vehicle entering the lane; when the vehicle is sensed, outputting a trigger signal; Recognize the multiple characteristic information of the vehicle in response to a trigger signal; output the recognition result of each characteristic information, wherein the recognition result includes the trigger time of sensing entering the lane, and the trigger time is when the identification device of the characteristic information receives the trigger The current system time of the identification device at the time of the signal; and pairing the identification results output by these identification devices with the same trigger time of the same lane as the identification feature record group belonging to the same vehicle number.

101~103: Feature information identification equipment

201: Vehicle induction trigger device

301: Device time correction service host

401: Feature Information Pairing Device

601: Identify lane attachment facilities

S01~S03, S11~S17, S21~S23: method steps

FIG. 1 and FIG. 2 are structural diagrams of a system for matching asynchronous identification results of vehicle characteristic information according to the present invention.

FIG. 3 is a flow chart of a method for pairing asynchronous identification results of vehicle characteristic information according to the present invention.

The following describes the technical content of the present invention through specific embodiments, and those skilled in the art can easily understand the advantages and effects of the present invention from the content disclosed in this specification. However, the present invention can also be implemented or applied in other different specific implementation forms.

FIG. 1 and FIG. 2 are schematic diagrams of a system for matching asynchronous identification results of vehicle characteristic information according to the present invention. The vehicle characteristic information asynchronous identification result matching system includes: plural characteristic information identification devices 101/102/103, vehicle induction trigger device 201, device time correction service host 301, characteristic information matching device 401 and identification lane attachment facility 601, Among them, the characteristic information identification device 101/102/103 and the characteristic information pairing device 401 are communicatively coupled to the device time correction service host 301, the vehicle induction trigger device 201 is communicatively coupled to the characteristic information identifying device 101/102/103, and the characteristic information identifying device 101/102/103 communication coupling feature information pairing device 401 .

In one embodiment, the lane identification attachment facility 601 can be an arch or a space under the ground of the lane, for the feature information identification devices 101/102/103 to be installed or buried thereon.

Feature information identification equipment 101/102/103 generally refers to equipment used to identify various feature information of vehicles passing through a lane through various vehicle identification technologies, wherein vehicle feature information includes but not limited to: license plate number, vehicle weight, vehicle speed, axle number, vehicle type, and plural feature information in the electronic tag. In identifying lanes, depending on the items of feature information that need to be identified, two or more types of feature information identification devices may exist at the same time. For example, the feature information identification device 101 can be a wireless signal transceiver for identifying electronic tags of vehicles. The characteristic information identification device 102 can be a digital camera or a video camera, and is used to identify at least one of the license plate number, the number of axles and the vehicle type of the vehicle. The characteristic information identifying device 103 may include an electronic scale and other types of detectors or sensors, and is used to identify at least one of the vehicle weight, vehicle speed, number of axles, and vehicle type. In other embodiments, fewer or more types of feature information identification devices may be used according to application requirements.

The vehicle induction trigger device 201 is used to sense the vehicle entering the identification lane, and the vehicle induction method includes but not limited to geomagnetic induction coil, laser distance measurement, infrared ray interception, radar distance measurement, and ultrasonic distance measurement and other trigger methods, and When a vehicle is sensed, a trigger signal is output to the feature information identification device 101/102/103 and the feature information pairing device 401 for time synchronization.

In addition, the vehicle sensing trigger device 201 can provide the lane information of the vehicle and output the trigger signal to the characteristic information identification device 101/102 according to the order of its lanes (such as the first lane, the second lane, etc.) or the lane position (such as longitude and latitude, etc.) /103 is paired with the device 401 with feature information.

The device time correction service host 301 provides a single standard time for other devices that identify lanes to perform system time synchronization correction.

The characteristic information pairing device 401 receives the characteristic recognition results completed by the characteristic information recognition devices 101/102/103 from the characteristic information recognition devices 101/102/103, and records the lanes belonging to the same lane according to the matching method of the characteristic information recognition results provided by the present invention. Vehicles of the same trip are identified by different identification devices Prepare the feature recognition results generated independently at different times, and perform correct matching to output a unique feature information record set for a single trip.

In another embodiment, the feature information pairing device 401 can also record the feature recognition results independently generated by different recognition devices at different times for vehicles belonging to different lanes but the same car number, and perform correct matching to output a single car number Dedicated feature information record group.

All devices for identifying lanes, including feature information identification devices 101/102/103 and feature information pairing device 401, use standard time correction protocols, such as Network Time Protocol (Network Time Protocol, NTP), etc., according to device time correction services The single standard time provided by the host 301 is continuously automatically adjusted to correct the system time of each device, thereby maintaining the synchronization of the system time among all devices. The plurality of feature information identification devices 101/102/103 independently identify the feature information of asynchronous passing vehicles according to the identification technology of each device and the feature information required for identification.

When the vehicle to be recognized enters the recognition lane, the single vehicle sensing trigger device 201 of the lane outputs a single trigger signal when it senses the vehicle, and transmits the trigger signal synchronously to all the feature information recognition devices 101/102/103 of the lane. When each of the feature information identification devices 101/102/103 receives the trigger signal, they will mark the current system time on the self-identification device (hereinafter referred to as the trigger time), and when the current feature information identification is completed, Afterwards, the trigger time and the recognition result are output to the characteristic information pairing device 401 together. Then, the feature information pairing device 401 integrates the trigger times in the recognition results from the plurality of feature information identification devices 101/102/103, and matches the recognition results with the same trigger time of the same lane as the feature information belonging to the same vehicle number.

In one embodiment, when a vehicle enters the recognized lane, if it switches lanes, it can also use the feature recognition results independently generated by different recognition devices at different times for vehicles belonging to different lanes but the same vehicle number, and perform correct pair.

The matching method of the asynchronous identification results of related vehicle feature information is shown in FIG. 3 , and is described in detail as follows.

Step S01: The equipment for identifying lanes, including the characteristic information identification equipment 101/102/103 and the characteristic information pairing equipment 401, automatically and continuously with the equipment time adjustment service host 301 through a standard time adjustment protocol, such as Internet Time Protocol, etc. The time calibration operation is carried out to continuously maintain the system time synchronization among all equipment for identifying lanes.

Step S02: Define the maximum identification time T _101MAX /T _102MAX /T _103MAX required for each feature information identification device 101/102/103 to complete the feature information identification of a single trip, wherein, according to various feature information identification devices 101/102/ The identification methods, technologies, and requirements of 103 are different. The maximum identification time T _101MAX /T _102MAX /T _103MAX of each feature information identification equipment is a system parameter, which may be a fixed value, or may change due to the average speed of the lane, and is the The function value of the average vehicle speed (T _101MAX /T _102MAX /T _103MAX =f(average vehicle speed)). In addition, the fixed value can be set differently according to different road conditions, or different values can be analyzed or calculated according to different identification methods, technologies, and requirements, so as to provide the best maximum identification time and reduce the matching error rate .

Step S03: Define the maximum identification time T _MAX required for a single train. According to the difference in maximum recognition time T _101MAX /T _102MAX /T _103MAX of all feature information recognition devices 101/102/103 for recognizing lanes, take the maximum (T _MAX =MAX(T _101MAX , T _102MAX , T _103MAX )). In this embodiment, the time T _MAX is defined as the maximum identification time required for a single train.

Step S11: The vehicle sensing trigger device 201 waits for the vehicle to enter the identification lane, and outputs a trigger signal S to the feature information identification device 101/102/103 and the feature information pairing device 401 when a vehicle is detected for time synchronization.

Step S12: Recognize all the characteristic information of the lane. Each time the identification device 101/102/103 receives the trigger signal S output by the vehicle sensor trigger device 201, it records the current system time of the characteristic information identification device 101/102/103 as Trigger time T _S . In addition, each time the characteristic information pairing device 401 receives the trigger signal S output by the vehicle sensing trigger device 201 , it also records the current system time of the characteristic information pairing device 401 itself as the trigger time T _S .

Step S13: For the vehicle to be identified entering the identification lane, after receiving the trigger signal S from the single vehicle sensor trigger device 201 in the lane, the multiple feature information identification devices 101/102/103 use different identification techniques and required identification feature information , respectively carry out the asynchronous vehicle characteristic information identification operation of the current train number.

Step S14: The feature information identification devices 101/102/103 for identifying lanes respectively check whether the identification of vehicle feature information has been completed. If completed, the flow goes to step S15, otherwise the flow goes to step S16.

Step S15: After the characteristic information identification equipment 101/102/103 completes the asynchronous identification operation of the current train number, record its trigger time T _S in the identification results R ₁₀₁ , R ₁₀₂ , and R ₁₀₃ of the current train number and output them together Go to the characteristic information pairing device 401, and then the process enters step S21.

Step S16: The feature information identification devices 101/102/103 for lane identification check whether the time difference between the current system time and the trigger time T _S exceeds the maximum identification time T _101MAX /T _102MAX /T _103MAX of the feature information identification devices. If it has exceeded, the process goes to step S17, otherwise the process returns to step S13 to continue the identification of the asynchronous vehicle characteristic information of the current train.

Step S17: When the characteristic information identification device 101/102/103 receives the trigger signal S of the single vehicle induction trigger device 201 in the lane, after the maximum identification time T _101MAX /T _102MAX /T _103MAX of each characteristic information identification device, it still When the identification of the characteristic information of the train number cannot be completed. Then the identification result of the feature information of the train number is output as unidentifiable, and then the process returns to step S11.

Step S21: Since the identification time required for different characteristic information is different, _the characteristic information pairing device 401 will receive the identification _{results R 101 ,} R ₁₀₂ , R ₁₀₃ . Then, the feature information pairing device 401 performs time-synchronized pairing on the trigger time T _S of the pen test record recorded in the identification results of different feature information identification devices 101/102/103, and will come from the same lane and have the same trigger time. The identification results R ₁₀₁ , R ₁₀₂ , and R ₁₀₃ of T _S are paired into an identification feature record group {R ₁₀₁ , R ₁₀₂ , R ₁₀₃ } belonging to the same train number.

Step S22: The characteristic information pairing device 401 checks whether the pairing operation of all identification results generated by the characteristic information identification device 101/102/103 has been completed. If the pairing operation has been completed, the process returns to step S11, otherwise the process enters step S23.

Step S23: The characteristic information pairing device 401 checks whether the time difference between the current system time and its trigger time T _S has exceeded the maximum identification time T _MAX of a single vehicle. If not, the flow returns to step S21 to continue receiving and pairing the recognition result. If it has exceeded, then abandon the matching operation of the unreceived identification results (such as R ₁₀₃ ), and directly pair the remaining identification results that have been received (such as R ₁₀₁ and R ₁₀₂ ) as identification feature record groups that belong to the same vehicle number {R ₁₀₁ , R ₁₀₂ }, then the flow returns to step S11.

It should be noted that in step S11 , the vehicle sensing trigger device 201 waits for the vehicle to enter the identified lane, which means that the vehicle enters the same lane.

However, in another embodiment, it may also refer to switching lanes when the vehicle enters the lane, which may also be applicable. Or, when the vehicle enters the lane and switches lanes (that is, the lane order or lane position is changed to the adjacent lane in a short period of time), it will trigger the trigger signal of different lanes, and within a preset trigger time (which can be adjusted according to the speed of the vehicle, such as 1 second) can be paired as the identification feature record group of the same vehicle number to perform steps similar to those shown in Figure 3.

In detail, in some embodiments, part of the feature information identification device 101/102/103 of the lane may fail to successfully complete the vehicle feature identification of the current vehicle due to various factors, resulting in no identification results R ₁₀₁ , R ₁₀₂ , R ₁₀₃ output. After the feature information pairing device 401 receives the trigger signal S output by the vehicle sensor trigger device 201 for the current vehicle number, it will not report the identification result _R after waiting for the maximum identification time T _MAX required for the current vehicle number at most. The feature information identification devices 101/102/103 of , R ₁₀₂ , and R ₁₀₃ are automatically regarded as incomplete identification, and the pairing operation of the identification result of the feature information identification device for the current train number is abandoned. In addition, when one of the recognition results R ₁₀₁ , R ₁₀₂ , and R ₁₀₃ received by the characteristic information pairing device 401 is unrecognizable, the characteristic information pairing device 401 also abandons the pairing operation of the recognition result for the train number. The discarded identification results will not be added to the identification feature record group of the current train number, and the feature information matching device 401 directly uses the rest of the feature information identification results that have been identified to perform matching operations to improve efficiency.

From the above, it can be known that since all the characteristic information identification devices 101/102/103 of the lane have passed the time adjustment agreement, they have automatically adjusted the time with the equipment time adjustment service host 301, and continuously maintain the system time synchronization among all the devices in the lane. Therefore, the vehicle feature information asynchronous identification result matching system and method provided by the present invention is to use the single-lane vehicle induction trigger device 201 to sense the current vehicle number in the lane, and output the unique vehicle number trigger signal S to the lane All feature information identifies devices 101/102/103. All feature information identification devices 101/102/103 can be synchronously marked with the trigger time T _S through the unique trigger signal S of the train number, and all feature information identification devices 101/102/103 can complete the identification operation output respectively The trigger time T _S is output together with the identification results R ₁₀₁ , R ₁₀₂ , and R ₁₀₃ . When the feature information pairing device 401 performs the matching operation of the identification results R ₁₀₁ , R ₁₀₂ , R ₁₀₃ , it can use the trigger time T _S in the different identification results R ₁₀₁ , R ₁₀₂ , R ₁₀₃ to perform matching of identification results with high accuracy Operation.

To sum up, in the vehicle feature information asynchronous identification result matching system and method provided by the present invention, even if the identification results output by various feature information identification devices are greatly different due to the large difference in identification time requirements, the time required for the asynchronous output of the identification results When there is a drop, you can still pass through the different identification results Synchronize information at the same trigger time, and then confirm the feature recognition information belonging to the same train. In particular, the pairing system and method of the present invention can overcome the difficulties of the conventional technology, and can support the high-time-accuracy synchronization requirement for identification results in an environment with high traffic density and high-speed traffic flow. Compared with the traditional conventional technology, the matching system and method of the present invention can reduce the matching error rate by more than 50% under the premise of not needing to establish a known matching database in advance, and in the environment of high vehicle speed and high traffic density. It can effectively avoid the personal information and legal problems related to the prior art when the license plate and electronic tag pairing information must be obtained in advance.

The above detailed description is a specific description of the feasible embodiment of the present invention, but the embodiment is not used to limit the patent scope of the present invention, and all equivalent implementations or changes that do not deviate from the technical spirit of the present invention shall be included in this case within the scope of the patent.

101~103: Feature information identification equipment

201: Vehicle induction trigger device

301: Device time correction service host

401: Feature Information Pairing Device

601: Identify lane attachment facilities

Claims (9)

A system for pairing asynchronous identification results of vehicle characteristic information, comprising: a vehicle sensing trigger device for sensing a vehicle entering a lane, and outputting a single trigger signal when the vehicle is sensed; plural characteristic information identification devices for responding to the vehicle Identify multiple feature information of the vehicle with a single trigger signal, and then output the identification results of each feature information identification device, wherein the identification result includes the trigger time of sensing entering the lane, and the trigger time is received by the feature information identification device The current system time of the feature information identification device at the time of the single trigger signal; the feature information pairing device is used to pair the recognition results output by the feature information identification devices with the same trigger time of the same lane as belonging to the same vehicle Second, the identification feature record group; and the device time correction service host to provide a single standard time, wherein each feature information identification device is multiplexed to continuously calibrate the system of the feature information identification device according to the single standard time through a time correction protocol Time, to maintain the synchronization of the system time of the feature information identification equipment. The system for asynchronous identification result matching of vehicle characteristic information as described in Claim 1, wherein the time correction protocol is a network time protocol. The system for pairing asynchronous identification results of vehicle characteristic information as described in claim 1, wherein the vehicle induction triggering device adopts a geomagnetic induction coil, laser ranging, infrared interception, radar ranging or ultrasonic ranging The detection trigger method senses the vehicle, and the characteristic information of the vehicle includes the license plate number, vehicle weight, vehicle speed, number of axles, vehicle model and plural characteristic information in the electronic tag. The system for pairing asynchronous identification results of vehicle characteristic information as described in Claim 1, wherein the characteristic information identification devices independently perform asynchronous identification of the characteristic information of the vehicle. The system for pairing vehicle characteristic information asynchronous recognition results as described in claim 1, wherein, when each characteristic information recognition device receives the single trigger signal and passes the maximum recognition time of the characteristic information recognition device, it still fails to When the identification of the characteristic information of the vehicle is completed, the identification result of the characteristic information of the vehicle is output as unidentifiable. The system for pairing asynchronous identification results of vehicle characteristic information as described in Claim 5, wherein the maximum identification time of each characteristic information identification device is a fixed value or a function value of the average vehicle speed of the lane. The system for pairing vehicle characteristic information asynchronous identification results as described in Claim 1, wherein the characteristic information pairing device is multiplexed to abandon the pairing after receiving the single trigger signal and waiting for the maximum identification time of the vehicle Among the feature information identification devices, the identification results of the feature information identification devices that have not yet output the identification results are paired, and the other identification results that have been identified are directly used for the pairing operation. The system for pairing asynchronous identification results of vehicle characteristic information as described in Claim 7, wherein the maximum identification time of the vehicle is the maximum value among the maximum identification times of the characteristic information identification devices. A method for matching asynchronous identification results of vehicle characteristic information, comprising: sensing a vehicle entering a lane; outputting a single trigger signal when sensing the vehicle; identifying multiple characteristic information of the vehicle in response to the single trigger signal; outputting each characteristic The identification result of the information, wherein the identification result includes the trigger time for sensing entry into the lane, and the trigger time is the current system time of the identification device when the identification device of the characteristic information receives the single trigger signal; Pair the identification results output by these identification devices with the same trigger time of the same lane as the identification feature record group belonging to the same vehicle number; and continuously correct the system time of each identification device according to a single standard time through the time correction agreement , to maintain the synchronization of the system time of these identification devices.

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