Method and system for identifying abnormal navigational speed behavior of ship entering and leaving port

Abstract

The invention provides a method and a system for identifying abnormal ship speed entering and leaving behaviors, which are applied to the technical field of shipping safety monitoring, and the method comprises the steps: obtaining a ship AIS data point sequence, judging whether the geographic positions of continuous data points fall into a geo-fence or not based on the geo-fence and a speed threshold value, and if yes, executing the step 2; according to the scheme, the sudden change process of the navigational speed can be accurately recognized instead of only the abnormal state, the technical problem that early warning is not timely in the prior art is solved, and the navigational speed early warning method and device have the advantages of being capable of accurately recognizing the sudden change process of the navigational speed and not only recognizing the abnormal state of the navigational speed. Therefore, early-stage and accurate early warning of abnormal ship entering and leaving speed behaviors is realized.

Description

TECHNICAL FIELD

[0001] A method and system for identifying abnormal behavior of a ship's speed when entering or leaving a port BACKGROUND

[0002] With the rapid development of global shipping industry, the traffic flow of ships in ports and waterways is increasingly dense, and the management of navigation safety and efficiency is put forward with higher requirements. In traffic-intensive or restricted water areas such as ports and waterways, the speed of ships is a parameter that needs to be strictly controlled. Too fast speed may lead to major safety accidents such as collision and grounding; too slow speed will reduce the efficiency of waterway traffic and cause congestion.

[0003] Currently, the maritime monitoring system can monitor the instantaneous speed of a ship using Automatic Identification System (AIS) data. When the speed of a ship exceeds the maximum limit or is lower than the minimum limit, the system can issue an alarm. For example, Chinese patent applications CN116257565A and CN117570997A disclose methods for monitoring the speed of a ship in a specific water area, the logic of which is to determine whether the instantaneous speed value of a ship at a certain time falls outside a pre-set normal interval.

[0004] However, the existing technology has a technical defect: it can only identify that the speed of a ship is in an abnormal state, but cannot identify the process of abnormal change in speed. For example, the speed of a ship may suddenly drop from 10 knots of normal speed to 4 knots below the minimum speed of 5 knots in a short time. The existing technology can only trigger an alarm when the speed drops below 5 knots, which may have missed the opportunity for early warning and intervention. This "sudden process" from normal to abnormal is itself more dangerous and valuable information than the abnormal state result, but the existing technology cannot effectively identify it. This lag in early warning may cause the maritime management department to miss the best opportunity to take intervention measures such as collision avoidance and waterway control, thus failing to effectively reduce the probability of accidents.

[0005] Therefore, there is a need in the art for a technical solution that can accurately identify the process of "sudden speed reduction" or "sudden speed increase" of a ship, thereby achieving earlier risk warning.

[0006] It should be noted that the information disclosed in the above background section is only used to strengthen the understanding of the background of the present application, and therefore can include information that does not constitute prior art known to those of ordinary skill in the art. SUMMARY

[0007] In view of this, the present application provides a kind of ship in and out of port speed abnormal behavior identification method and system, to solve the technical problems that only the instantaneous speed of ship can be judged in prior art, and the process behavior of " sudden speed reduction " or " sudden acceleration " of ship speed cannot be effectively identified, by obtaining the continuous AIS time series data of ship, and based on the preset channel geographic fence and navigation rule threshold, using the sliding window containing two consecutive data points, whether the preset state transition of ship speed state occurs is judged, to identify the speed change behavior of ship, to realize the accurate identification and timely warning of ship speed mutation behavior.

[0008] The embodiment of the present application provides a kind of ship in and out of port speed abnormal behavior identification method, comprising: a series of time-ordered AIS data points containing target ship geographic position and ground speed are obtained; based on the pre-stored geographic fence for limiting ship channel on map and the speed threshold associated with geographic fence; select the current data point and the previous data point in time sequence of AIS data points, judge whether the geographic position of current data point and previous data point falls into geographic fence; in response to the geographic position of current data point and previous data point falls into geographic fence, based on speed threshold, judge whether the ground speed of previous data point is in normal speed interval, and whether the ground speed of current data point is in abnormal speed interval; when the ground speed of previous data point is in normal speed interval, and the ground speed of current data point is in abnormal speed interval, generate warning signal for indicating that ship speed abnormal behavior occurs.

[0009] In some optional embodiments, the abnormal speed interval is lower than the preset minimum speed threshold.

[0010] In some optional embodiments, the abnormal speed interval is higher than the preset maximum speed threshold.

[0011] In some optional embodiments, the method further comprises: after generating warning signal, continue to obtain and judge the ground speed of subsequent AIS data points, when detecting that the ground speed returns to normal speed interval from abnormal speed interval, generate end signal for indicating that speed abnormal behavior ends.

[0012] In some optional embodiments, the method further comprises: When it is judged that the geographic position of the previous data point is located outside the geo-fence and the geographic position of the current data point is located inside the geo-fence, the step of generating the early warning signal is not executed.

[0013] In some optional embodiments, the method further comprises: Before the step of generating the early warning signal, the method further comprises: Based on the pre-stored acceleration threshold associated with the geo-fence, the rate of change of the airspeed between the current data point and the previous data point is calculated, and it is judged whether the absolute value of the rate of change of the airspeed is greater than the acceleration threshold; The early warning signal is generated when the absolute value of the rate of change of the airspeed is greater than the acceleration threshold.

[0014] In some optional embodiments, the step of calculating the rate of change of the airspeed comprises: The respective time stamps are extracted from the current data point and the previous data point; The time difference is calculated based on the time stamps; The difference in airspeed between the current data point and the previous data point is divided by the time difference to obtain the rate of change of the airspeed.

[0015] In some optional embodiments, the pre-stored geo-fence is divided into a plurality of sub-regions of the airway, and a set of airspeed thresholds is independently associated with each sub-region of the airway.

[0016] In some optional embodiments, the method further comprises: Before the step of judging whether the geographic positions of the current data point and the previous data point are both inside the geo-fence, the sub-region of the airway to which the current data point and the previous data point both belong is first determined according to the geographic positions of the current data point and the previous data point, and the set of airspeed thresholds associated with the sub-region of the airway is called for subsequent judgment.

[0017] In some optional embodiments, the step of generating the end signal specifically comprises: When the airspeed is detected to return to the normal airspeed interval from the abnormal airspeed interval, it is continued to be judged whether the airspeed of the subsequent at least one AIS data point continuously remains in the normal airspeed interval; After it is determined that the airspeed continuously remains in the normal airspeed interval, the end signal is generated.

[0018] In some optional embodiments, the method further comprises: When it is judged that the geographic position of the previous data point is located inside the geo-fence and the geographic position of the current data point is located outside the geo-fence, if there is an airspeed abnormal behavior for which an early warning signal has been generated but an end signal has not been generated, the end signal is generated.

[0019] In some optional embodiments, the pre-stored geo-fence is divided into a plurality of channel sub-regions, and a set of speed threshold values and acceleration threshold values are independently associated with each channel sub-region.

[0020] In some optional embodiments, the method further comprises: Before the step of determining whether the geographic locations of the current data point and the previous data point both fall within the geo-fence, first determine the channel sub-region to which the current data point and the previous data point both belong according to their geographic locations, and call the set of speed threshold values and the set of acceleration threshold values associated with the channel sub-region for subsequent determination.

[0021] In some optional embodiments, the obtained series of AIS data points are continuous data streams from the same target ship.

[0022] In some optional embodiments, the generated early warning signal contains the timestamp, geographic location, speed over ground, and type of abnormal speed interval of the current data point.

[0023] Embodiments of the present application provide a ship entering and leaving port speed abnormal behavior recognition system, comprising: A data acquisition module configured to obtain a series of time-ordered automatic identification system (AIS) data points containing the geographic location and speed over ground of a target ship; A storage module configured to store a geo-fence for defining a ship channel on a map and speed threshold values associated with the geo-fence; A processor communicatively connected to the data acquisition module and the storage module, the processor being configured to: Select a current data point and a previous data point that are time-continuous in the sequence of AIS data points, and determine whether the geographic locations of the current data point and the previous data point both fall within the geo-fence stored in the storage module; In response to the geographic locations of the current data point and the previous data point both falling within the geo-fence, determine whether the speed over ground of the previous data point is in a normal speed interval and whether the speed over ground of the current data point is in an abnormal speed interval based on the speed threshold values; A signal generation module communicatively connected to the processor, the signal generation module being configured to: When the processor determines that the speed over ground of the previous data point is in the normal speed interval and the speed over ground of the current data point is in the abnormal speed interval, generate an early warning signal indicating that the ship has a speed abnormal behavior.

[0024] In some optional embodiments, the processor is further configured to: After the signal generation module generates the early warning signal, continue to obtain and determine the speed over ground of subsequent AIS data points; The signal generation module is further configured to: When the processor detects that the ground speed is restored from the abnormal speed interval to the normal speed interval, an end signal indicating that the speed abnormal behavior ends is generated.

[0025] In some optional embodiments, the storage module is further configured to store an acceleration threshold value associated with the geo-fence; The processor is further configured to: After determining the interval in which the ground speed is located, the rate of change of speed between the current data point and the previous data point is calculated, and it is determined whether the absolute value of the rate of change of speed is greater than the acceleration threshold value; The signal generation module is specifically configured to: When the processor determines that the absolute value of the rate of change of speed is greater than the acceleration threshold value, a pre-warning signal is generated.

[0026] In some optional embodiments, the geo-fence stored in the storage module is divided into a plurality of channel sub-regions, and a set of speed threshold values is independently associated with each channel sub-region; The processor is further configured to: Before determining whether the geographic positions of the current data point and the previous data point both fall within the geo-fence, first determine the channel sub-region to which they both belong according to the geographic positions of the current data point and the previous data point, and call the set of speed threshold values associated with the channel sub-region for subsequent determination.

[0027] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit the present application.

[0028] The ship in-out port speed abnormal behavior recognition method and system of the present application has the following beneficial effects: The present application can earlier warn the ship in-out port speed abnormal behavior by recognizing the mutation process of speed from normal to abnormal rather than only monitoring the abnormal state, so as to gain more sufficient intervention time. At the same time, since the mutation process of speed is considered, by quantifying the rate of change of speed and determining whether it exceeds the preset acceleration threshold value, the dangerous "mutation" and the normal "slow change" can be effectively distinguished, the false alarm caused by the normal speed change of the ship crossing the threshold in the prior art is significantly reduced, the warning information is more valuable, the accuracy of the warning is improved, and the navigation safety guarantee capability of the port channel is enhanced. BRIEF DESCRIPTION OF DRAWINGS

[0029] Other features, objects and advantages of the present application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings.

[0030] Figure 1 is the overall flowchart of the ship in-out port speed abnormal behavior recognition method provided by an embodiment of the present application; Figure 2 is a flow chart of a method for identifying abnormal behavior of a ship's speed when entering or leaving a port according to an embodiment of the present application; Figure 3 is a schematic diagram of a ship's track and a sliding window according to an embodiment of the present application; Figure 4 is a schematic diagram of a time axis of a process for identifying abnormal behavior of a ship's speed according to an embodiment of the present application; Figure 5 is a schematic diagram of a structure of a system for identifying abnormal behavior of a ship's speed when entering or leaving a port according to an embodiment of the present application. DETAILED DESCRIPTION

[0031] Example implementations will now be described more fully with reference to the accompanying drawings. Example implementations may, however, be implemented in many different forms and should not be construed as limited to the implementations set forth herein; rather, these implementations are provided so that this disclosure will be thorough and complete, and will fully convey the scope of example implementations to those skilled in the art. The described features, structures, or characteristics can be combined in one or more implementations.

[0032] In addition, the accompanying drawings are included to provide a further understanding of the present application, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present application and, as such, a change in the drawings can be made for clarity ease of illustration. In the drawings, components having the same function are designated with the same reference numerals even though the components are illustrated in different drawings. Thus, the components can be omitted or simplified in some drawings for clarity of illustration. The same reference numerals can be used to represent the same elements throughout the specification and drawings.

[0033] The flow charts shown in the drawings are only illustrative and do not necessarily include all steps. For example, some steps can be further divided, and some steps can be combined or partially combined, and thus the order of actual execution can be changed according to actual conditions.

[0034] The automatic identification system (AIS) periodically broadcasts the dynamic information of a ship through radio communication technology, including the unique identification of the ship, the geographic position, the speed, etc. According to the AIS data, the navigation state of the ship can be monitored. The navigation behavior of the ship in the water area is affected by various factors, such as channel restrictions, traffic density, weather conditions, etc. The speed as a parameter of the navigation state of the ship directly reflects the maneuvering behavior and potential risks of the ship. Through the analysis of the historical AIS data of the ship, a statistical model of the normal navigation state of the ship can be established. When the actual speed of the ship deviates from the normal range, it may indicate the occurrence of potential danger or abnormal situation. By using the geographic fence technology, the activity range of the ship can be limited, and when the ship enters or leaves a specific area, the corresponding event is triggered. Combined with the speed threshold, it can be judged whether the speed of the ship in the specific area meets the safety requirements.

[0035] In order to make the objects, technical solutions and advantages of the present application clearer, the specific embodiments of the present application will be described in detail below with reference to the drawings.

[0036] Figure 1 is the overall flowchart of the ship speed abnormal behavior recognition method provided by an embodiment of the present application. Referring to Figure 1 , the method described in the present application can include the following steps: Firstly, the step of defining the approach channel and the speed threshold in the channel is performed. This step provides the basic rules and geographical boundaries for the subsequent recognition and judgment. In a specific implementation, this step includes defining one or more closed polygons as a geographic fence on an electronic map through a series of latitude and longitude coordinate points to limit the monitoring channel of the ship; at the same time, a set or multiple sets of speed rules are associated with each geographic fence, and the rules at least include the speed threshold (such as the minimum speed threshold and the maximum speed threshold) for defining the normal speed interval. These geographic fence coordinates and rule parameters are pre-stored in the storage module of the system.

[0037] Then, the step of collecting real-time AIS data of the ship is performed. The data collection module of the system continuously and real-timely acquires the AIS message broadcasted by the target ship through the AIS receiving device or the network interface, and parses the data points containing the time stamp, the geographic position and the speed over ground, etc. from the AIS message to form a time-ordered data point sequence.

[0038] Then, the application introduces a time series analysis logic based on consecutive data points to identify the "process" of speed change rather than just the "state". Specifically, the system adopts a sliding window of size 2, which always contains the current data point and the previous data point in time. The system compares the current point speed with the speed threshold to determine the speed state at the current time; at the same time, the system also compares the previous point speed with the speed threshold to determine the speed state at the previous time. These two comparison steps are the core of the application, aiming to obtain the speed state information of two consecutive time points to provide a basis for subsequent behavior judgment.

[0039] After the above comparison is completed, the step of judging whether there is a sudden speed reduction / acceleration is performed. The core task of this step is to analyze the speed state change between two consecutive data points. The basic judgment logic of this step is to judge whether the speed state of the ship has a preset transition from the normal speed interval to the abnormal speed interval between the previous data point and the current data point.

[0040] Finally, if the judgment result is yes, i.e., it is determined that the preset state transition occurs, the step of notifying relevant personnel when the speed is abnormal is performed. This step is usually performed by the signal generation module of the system, such as generating a structured warning signal containing information such as event time, position, speed, etc., and sending it to maritime monitoring personnel through the user interface, sound and light alarm or network interface.

[0041] It should be emphasized that, Figure 1 The figure shows a general flow of the application. In specific application scenarios, in order to obtain better technical effects, the above steps can include more refined technical solutions.

[0042] For example, in a preferred embodiment, the above-mentioned "judging whether there is a sudden speed reduction / acceleration" step can further include a quantitative judgment of the speed change rate to enhance the accuracy of identification. Specifically, after judging that the speed state has a transition, the processor will also calculate the actual speed change rate (i.e. acceleration) between the current data point and the previous data point according to the time stamp and the ground speed of the two points. Then, the processor compares the absolute value of the speed change rate with a preset acceleration threshold. Only when both the "state transition" and the "change rate exceeding the acceleration threshold" conditions are met, the system finally determines that there is an abnormal behavior of sudden speed reduction or acceleration and generates a warning signal. This scheme can effectively distinguish between dangerous speed mutations and slow speed changes caused by normal ship operation by quantifying the severity of "mutation", thereby significantly reducing the false alarm rate and improving the value of the warning information.

[0043] For another example, in another preferred embodiment, the step of "defining the approach channel and the speed threshold in the channel" can realize dynamic and fine management. Specifically, a complete channel can be divided into multiple channel sub-regions with different navigation characteristics (such as open area, narrow area, turning area, etc.), and a set of speed threshold and acceleration threshold suitable for each channel sub-region is configured independently. In runtime, the system will first determine the channel sub-region to which the ship belongs according to the current geographical position of the ship, and dynamically call the specific rule parameters associated with the sub-region for judgment. This scheme enables the recognition model to adapt to the complex and variable channel physical environment, further improving the accuracy and practicality of recognition.

[0044] As shown in Figure 2 The embodiments of the present application provide a ship entering and leaving port speed abnormal behavior recognition method, which comprises the following steps: Step S100: Obtain a series of time-ordered automatic identification system (AIS) data points containing the geographical position and the speed over ground of the target ship.

[0045] In this step, the AIS data is obtained through an AIS receiving device, which can be a shore-based AIS base station or a shipborne AIS transponder. The AIS data point at least contains the unique identification (MMSI) of the ship, the time stamp, the geographical position (latitude and longitude) and the speed over ground (SOG). The AIS data is transmitted in the form of a message and arranged in time sequence to form a data point sequence, for example {P1, P2,..., Pk,...}, where each Pk represents an AIS data point. The way to obtain AIS data includes but is not limited to receiving through radio frequency, receiving through network data interface, etc. In other optional embodiments, data can also be obtained through satellite AIS receiving devices to expand the monitoring range.

[0046] Step S200: Define the monitoring area and the judgment standard based on the pre-stored geographical fence for defining the ship channel on the map and the speed threshold associated with the geographical fence.

[0047] A geo-fence is a closed area defined on an electronic map to delimit a ship's sailing area. A geo-fence is composed of a series of ordered latitude and longitude coordinate points, which are stored in a data storage to define the range of a specific fairway. A speed threshold is one or more values associated with a geo-fence to determine whether a ship's speed is within a normal range. The speed threshold can include a minimum speed threshold and a maximum speed threshold. These thresholds are set according to the specific conditions of the fairway and are stored in the data storage in association with the corresponding geo-fence. In other optional embodiments, a geo-fence can also be defined in other forms, such as using a polygon object in a geographic information system (GIS). The speed threshold can also be a dynamic threshold adjusted according to time, weather, etc.

[0048] Step S300: Selecting a current data point and a previous data point in the AIS data point sequence that are continuous in time, and determining whether the geographical positions of the current data point and the previous data point are both within the geo-fence.

[0049] In this step, the system uses a sliding window of size 2, which contains two adjacent AIS data points in time: the current data point (Pk) and the previous data point (Pk-1). By calculating the relationship between the latitude and longitude coordinates of the ship and the boundary coordinates of the geo-fence, it is determined whether the data point is located within the geo-fence. The judgment algorithm includes but is not limited to the ray method, the point-in-polygon algorithm, etc. Only when both data points in the sliding window are within the geo-fence, the subsequent speed judgment is performed. In other optional embodiments, the size of the sliding window can be adjusted according to actual needs, for example, using a sliding window containing three or more data points.

[0050] Step S400: In response to the geographical positions of the current data point and the previous data point both being within the geo-fence, based on the speed threshold, determining whether the ground speed of the previous data point is within the normal speed interval and whether the ground speed of the current data point is within the abnormal speed interval.

[0051] In this step, first, the speed threshold associated with the current geo-fence is read from the storage. Then, it is determined whether the ground speed of the previous data point and the current data point is within the normal speed interval, respectively. The normal speed interval is determined by the minimum speed threshold and the maximum speed threshold. If the ground speed of the previous data point is higher than the minimum speed threshold and lower than the maximum speed threshold, it is considered to be within the normal speed interval. If the ground speed of the current data point is lower than the minimum speed threshold or higher than the maximum speed threshold, it is considered to be within the abnormal speed interval. In other optional embodiments, the definition of the normal speed interval can be more complex, for example, considering the fairway width, water depth, etc.

[0052] Step S500: the ground speed of the previous data point is in the normal speed interval, and the ground speed of the current data point is in the abnormal speed interval, a warning signal indicating that the ship has abnormal speed behavior is generated.

[0053] In this step, if the judgment result of step S400 indicates that the ground speed of the previous data point is in the normal speed interval, and the ground speed of the current data point is in the abnormal speed interval, the system generates a warning signal. The warning signal is used to indicate that the ship has abnormal speed behavior, such as sudden speed reduction or sudden acceleration. The warning signal can contain information such as the MMSI of the ship, the current timestamp, the geographic position, the ground speed and the type of abnormality. The warning signal can be displayed through the display, the alarm sound can be emitted through the speaker, or the network interface can be sent to other systems. In some other optional embodiments, the warning signal can also contain other information, such as the recommended measures.

[0054] Through the above steps, the identification of the abnormal speed behavior of the ship entering and leaving the port is realized. The data acquisition module acquires the AIS data, the storage module stores the geographic fence and the speed threshold, the processor executes the data processing and judgment logic, and the signal generation module generates the warning signal. These modules cooperate with each other and work together to solve the technical problem that the prior art cannot effectively identify the process behavior of the ship speed "sudden speed reduction" or "sudden acceleration", realize the change from "state monitoring" to "behavior identification", and can more early and accurately warn the abnormal speed behavior of the ship entering and leaving the port.

[0055] Through the above scheme, the present embodiment can effectively identify the abnormal speed behavior of the ship entering and leaving the port, realize the early warning of the abnormal speed behavior, and thus enhance the navigation safety guarantee capability of the port channel.

[0056] In order to more specifically illustrate the working principle of the present application, especially the sliding window mechanism and the processing of boundary conditions, the following will be described in detail with reference to Figure 3 .

[0057] As shown in Figure 3 , two vertical lines in the figure define the geographic fence boundary of a channel. The arrow indicates the direction of the ship. P1 to P6 represent six AIS data points continuously acquired by the system in time sequence, each point representing the geographic position of the ship at a certain time.

[0058] In the present embodiment, the system uses a sliding window with a size of 2 to analyze the data point sequence. The following will describe the execution details of the method of the present application in the process of moving the sliding window in the time sequence: Time T1: the system only acquires data point P1. At this time, since the data point is not enough to form a complete sliding window, the system does not make any judgment.

[0059] Time T2: The system acquires data point P2, and a first sliding window is formed, containing (P1, P2). The processor determines that the geographical position of P1 is outside the fairway, while the geographical position of P2 is inside the fairway. This belongs to the boundary case of a ship entering the fairway. According to the rules of the present application, the system does not perform the judgment of abnormal behavior of the speed of the ship in this sliding window to avoid false positives due to normal deceleration when entering the port.

[0060] Time T3: The system acquires data point P3, and the sliding window moves forward, containing (P2, P3). As shown by the dashed box in the figure. The processor determines that the geographical positions of P2 and P3 are both inside the fairway. At this time, the system enters the regular judgment process. The system will acquire the ground speed of P2 and P3 respectively, and judge their speed states according to the preset speed threshold. Assuming that the speed of P2 is normal, and the speed of P3 is abnormal (for example, lower than the minimum speed), the condition for state transition is met. In a preferred embodiment, the system will further calculate the speed change rate between (P2, P3) and compare it with the acceleration threshold. If all conditions are met, the system will generate a warning signal at time T3.

[0061] Time T4 and T5: Similarly, the system will process sliding windows (P3, P4) and (P4, P5) in turn. Since all data points in these two windows are inside the fairway, the system will continue to perform the regular abnormal behavior judgment logic of the speed of the ship.

[0062] Time T6: The system acquires data point P6, and the sliding window moves to contain (P5, P6). The processor determines that the geographical position of P5 is inside the fairway, while the geographical position of P6 is outside the fairway. This belongs to the boundary case of a ship leaving the fairway. According to the rules of the present application, the system will check whether there is an abnormal behavior of the speed of the ship associated with the ship that has not ended. If there is (for example, the warning event generated at time T3 has not ended), the system will generate an end signal at this moment to ensure the completeness of the event record.

[0063] Through the above detailed description with reference to Figure 3 , the working principle of the present application, which uses sliding windows to analyze consecutive data points and finely processes different scenarios such as entering, sailing in, and leaving the fairway, is clearly revealed.

[0064] In combination with Figure 4 and a scenario containing specific example data, the whole process of identifying abnormal behavior of the speed of the ship is described in detail.

[0065] With reference to Figure 4Fig. 1 is a time axis diagram of a ship abnormal speed behavior recognition process. In the figure, the dashed box from time T4 to time T14 represents a preset monitoring channel geographical range. The navigation rules set for the channel are pre-stored in the system's storage module, as follows: Minimum speed threshold : set to 5.0 knots. Therefore, Figure 4 AIS data points (such as P4, P5) represented by solid dots in the figure have a ground speed greater than or equal to 5.0 knots, and are in the "normal speed interval"; AIS data points (such as P6, P9) represented by hollow dots have a ground speed less than 5.0 knots, and are in the "abnormal speed interval".

[0066] Acceleration threshold : set to 0.8 knots / minute.

[0067] For ease of illustration, it is assumed that the time interval between each adjacent time point from T1 to T15 is 1 minute.

[0068] System execution flow analysis: This embodiment will describe how the system processes the AIS data point sequence from P1 to P15 using a sliding window in chronological order.

[0069] Time T1-T3: The system receives data points P1, P2, and P3 in turn. When processing the sliding windows (P1, P2) and (P2, P3), the processor determines that the geographical positions of these data points are all outside the preset channel, so no speed abnormal behavior judgment is performed.

[0070] Time T4: The system receives data point P4, forming sliding window (P3, P4). The processor determines that P3 is outside the channel and P4 is inside the channel. This case is identified as a "channel entry" boundary condition, and to avoid false positives due to normal port entry deceleration operations of the ship, the system does not perform abnormal behavior judgment in this sliding window.

[0071] Time T5: The system receives data point P5, forming sliding window (P4, P5). The processor determines that P4 and P5 are both inside the channel, and according to the figure, their speed states are both "normal" (solid dots). Since no state transition from normal to abnormal has occurred, the system does not generate a warning signal.

[0072] Time T6: The system receives data point P6, forming a sliding window (P5, P6). The processor determines that both P5 and P6 are within the channel. P5 has a speed state of "normal", while P6 has a speed state of "abnormal" (hollow circle), satisfying the condition for state transition. To further confirm whether it is a "sudden change", the system performs the acceleration judgment in the preferred solution: assuming the ground speed of P5 is 5.6 knots, and the ground speed of P6 is 4.3 knots, the absolute value of the speed change rate is |4.3 - 5.6| / 1 = 1.3 knots / min. This value is greater than the preset acceleration threshold of 0.8 knots / min. Since both the state transition and the change rate exceed the limit, the signal generation module generates a warning signal indicating "sudden speed reduction" at time T6.

[0073] Time T7: The system receives data point P7, forming a sliding window (P6, P7). P6 has a speed state of "abnormal", and P7 has a speed state of "normal". The system detects that the speed has returned to the normal speed interval from the abnormal speed interval, and therefore generates an end signal indicating that the abnormal behavior starting at time T6 has ended.

[0074] Time T8: The system processes the sliding window (P7, P8), and the speed states of both data points are "normal", generating no warning.

[0075] Time T9: The system receives data point P9, forming a sliding window (P8, P9). P8 has a state of "normal", and P9 has a state of "abnormal", satisfying the condition for state transition. Assuming the ground speed of P8 is 5.5 knots, and the ground speed of P9 is 3.2 knots, the absolute value of the speed change rate is |3.2 - 5.5| / 1 = 2.3 knots / min, which is greater than the acceleration threshold of 0.8. Both conditions are met, and the system generates a new "sudden speed reduction" warning signal at time T9.

[0076] Time T10 to T11: The system processes the sliding windows (P9, P10) and (P10, P11) in turn. In these windows, the speed state of the previous data point is "abnormal", not satisfying the condition for "from normal to abnormal" state transition, so the system does not generate a new warning signal, only maintaining the abnormal event starting at time T9 as active.

[0077] Time T12: The system receives data point P12, forming a sliding window (P11, P12). P11 has a state of "abnormal", and P12 returns to "normal". The system generates an end signal indicating that the abnormal behavior starting at time T9 has ended.

[0078] Time T13: The system processes the sliding window (P12, P13), and both points have a state of "normal", generating no warning.

[0079] Time T14: The system receives data point P14, forming a sliding window (P13, P14). P13 is in the state of “normal”, and P14 is in the state of “abnormal”, satisfying the state transition. Assuming that P13 has a speed of 5.4 knots, and P14 has a speed of 4.5 knots, the absolute value of the acceleration is 0.9, which is greater than 0.8. The double conditions are satisfied, and the system generates a warning signal at time T14.

[0080] Time T15: The system receives data point P15, forming a sliding window (P14, P15). The processor determines that P14 is within the channel, while P15 is outside the channel, which is a boundary case of “leaving the channel”. The system detects that the abnormal behavior since time T14 has not ended, so at this moment, an end signal is forcibly generated to ensure the completeness of the event record.

[0081] Through the above detailed step-by-step demonstration combined with Figure 4 , the present application can accurately identify three dangerous speed mutation behaviors at times T6, T9, and T14, and accurately confirm the end of the abnormal state at times T7, T12, and T15. This fully demonstrates that the present application has significant technical progress in the timeliness, accuracy, and logical integrity of the warning compared to the prior art.

[0082] In a specific embodiment, on the basis of the above-mentioned embodiment, when the ship's ground speed is lower than the preset minimum speed threshold, the speed state is defined as “too low” or “abnormal” by the speed state judgment module. First, the system reads the preset minimum speed threshold from the storage module, which is pre-configured by the administrator and associated with a specific geographic fence or channel sub-region. Specifically, the speed state judgment module compares the ground speed SOG in the current AIS data point provided by the data acquisition module with . Then, if SOG is less than , it is determined that the speed state represented by the data point is “too low”, and the data point is marked as an abnormal state. Wherein: SOG represents the ground speed of the current AIS data point; represents the preset minimum speed threshold. Then, the state information is passed to the subsequent abnormal behavior identification module for determining whether to trigger a warning signal. In some other optional embodiments, the minimum speed threshold can be dynamically adjusted according to the time period, for example, appropriately reducing the value of at night or in bad weather conditions to adapt to different navigation conditions.

[0083] Through the above scheme, the present embodiment can accurately identify the abnormal state of the ship below the minimum speed threshold, providing an accurate state basis for subsequent warning judgment.

[0084] In a specific embodiment, on the basis of the above-mentioned embodiments, the abnormal speed interval is defined as the speed of the ship over the preset maximum speed threshold. First, the system pre-stores a maximum speed threshold in the storage module for a specific geo-fence or channel sub-region . Specifically, when judging the speed state of the ship, the system compares the ground speed of the current AIS data point with the maximum speed threshold . The comparison process follows the following judgment formula:

[0085] Wherein: represents the ground speed of the current AIS data point, represents the preset maximum speed threshold. Then, if the above judgment formula is established, it is determined that the speed state of the data point is "too high", that is, in the abnormal speed interval. Then, if the speed state of the previous data point is "normal" (i.e., its ground speed is not greater than ), and the speed state of the current data point is "too high", the system identifies a state transition from normal to abnormal, and can further combine other conditions (such as the speed change rate) to judge whether to generate a warning signal indicating the "sudden acceleration" behavior. In some optional embodiments, the maximum speed threshold may not be a fixed value, but a dynamic threshold associated with the type, draft depth and other static or dynamic information of the ship, for example, the of a large oil tanker can be set to 12 knots, and the of a small passenger ship can be set to 18 knots.

[0086] Through the above scheme, the embodiment can accurately identify the abnormal state of the ship speed exceeding the maximum speed limit, and provides a technical basis for effectively avoiding safety risks caused by excessive speed of the ship.

[0087] In a specific implementation, on the basis of the above embodiment, after generating the early warning signal for indicating the abnormal speed behavior of the ship, the system continues to monitor the speed state of the ship. Specifically, the system continues to obtain subsequent AIS data points, and judges whether the ground speed of these data points is in the abnormal speed interval based on the preset geofence and speed threshold. Then, the system detects whether the ground speed has shifted from the abnormal speed interval to the normal speed interval. When detecting such a shift, the system generates an end signal for indicating the end of the speed abnormal behavior. In other optional implementations, the system can also trigger the generation of the end signal by judging whether the ship has exited the preset geofence area, or receiving manual intervention instructions, etc.

[0088] Through the above scheme, the embodiment can timely and accurately determine the end time of the speed abnormal behavior of the ship entering and exiting the port, avoid the continuation of the early warning state, and enable the monitoring system to more comprehensively reflect the actual sailing state of the ship.

[0089] In a specific implementation, on the basis of the above embodiment, first, after the system judges whether the geographic positions of the current data point and the previous data point are both within the geofence, the system judges the positional relationship between the previous data point and the current data point. Specifically, it is judged whether the geographic position of the previous data point is outside the geofence and the geographic position of the current data point is within the geofence. If the judgment result is yes, it indicates that the ship is entering the channel. Then, the system will not perform the step of generating the early warning signal, even if the judgment result according to the speed threshold at this time meets the early warning condition. In this way, false alarms caused by normal deceleration of the ship entering the port can be avoided. In other optional implementations, different geofence algorithms (for example, judging the distance between the data point and the geofence instead of the absolute inside-outside relationship) can be used to define the state of the ship "entering" the channel, and a configurable port entry mode switch can also be set to apply this rule only when the port entry mode is turned on.

[0090] Through the above scheme, the embodiment can avoid false alarms caused by normal deceleration of the ship entering the monitoring channel, and improve the accuracy and reliability of the early warning system.

[0091] In one specific implementation, on the basis of the above embodiment, first, the system obtains the pre-set acceleration threshold associated with the target geofence from the storage module. The acceleration threshold represents the speed limit that is considered as "sudden" acceleration or deceleration within a specific channel. Specifically, the threshold can be obtained by statistical analysis of historical AIS data, or can be set by manual according to the environmental characteristics and safety requirements of the specific channel. Then, before judging the speed state of the current data point and the previous data point, the system calculates the speed change rate between the two data points. The change rate is obtained by analyzing the speed difference of the two data points in time, which reflects the degree of change of the ship's speed per unit time. Then, the system judges whether the absolute value of the calculated speed change rate is greater than the pre-set acceleration threshold. If the absolute value of the speed change rate is less than or equal to the threshold, it is considered that the speed change of the ship is gentle and normal, and it does not belong to the abnormal behavior that needs to be warned. Only when the absolute value of the speed change rate is greater than the threshold, it is considered that the ship has "sudden" acceleration or deceleration behavior, and combined with the judgment result of the speed state, the final decision is made whether to generate a warning signal. In other optional implementations, the acceleration threshold can be dynamically adjusted according to different ship types, draft or weather conditions to adapt to more complex navigation environment.

[0092] Through the above scheme, the present embodiment can more accurately identify the abnormal mutation behavior of the ship's speed. Compared with the scheme that only relies on the speed threshold, the present embodiment not only considers the state of the speed itself, but also considers the degree of speed change, so as to effectively filter out the slow speed change caused by normal operation or environmental factors, significantly reduce the false positive rate, and improve the practicality and reliability of the warning system.

[0093] In one specific implementation, on the basis of the above embodiment, the calculation process of the speed change rate is performed by the processor 30, specifically including: first, extracting the respective time stamps and from the current data point and the previous data point respectively. In one specific implementation, the time stamp is a unified UTC time or Unix time stamp to ensure the accuracy of time calculation. Then, the processor 30 divides the difference of the ground speed of the current data point and the previous data point by the time difference between them, thereby obtaining the accurate speed change rate. The speed change rate A is calculated by the following formula:

[0094] wherein A represents the speed change rate, which can be in knots per second or knots per minute; represents the ground speed of the current data point ; represents the time stamp of the previous data point represents the ground speed of the previous data point represents the time stamp of the current data point represents the time stamp of the previous data point represents the time stamp of the previous data point represents the time stamp of the previous data point

[0095] By dividing the difference of ground speed by the actual time difference (t2-t1), the embodiment can adapt to the reality of uneven AIS data reporting intervals, ensuring the accuracy of the calculation of the rate of change of speed. The absolute value of the calculated rate of change of speed A can then be used for comparison with the preset acceleration threshold. Through the above scheme, the embodiment can accurately calculate the instantaneous rate of change of speed of the ship, providing a reliable technical basis for accurately identifying the sudden change process of the speed of the ship.

[0096] In a specific embodiment, on the basis of the above embodiment, the waterway is pre-divided into a plurality of sub-regions that do not overlap in geography. Specifically, the division of the waterway can include but is not limited to factors such as the width, depth, curvature, and historical accident rate of the waterway. For example, regions where ships frequently intersect, or regions with shallow water depth, can be divided into independent sub-regions. Each sub-region corresponds to a unique identifier, such as sub-region A, sub-region B, etc. Then, a set of speed thresholds is independently associated with each sub-region. The speed threshold includes a maximum speed threshold and / or a minimum speed threshold. For example, in a sub-region where ships frequently intersect, a lower maximum speed threshold can be set to reduce the risk of collision; while in a sub-region with shallow water depth, a higher minimum speed threshold can be set to avoid ship grounding. The correspondence between the sub-region and the speed threshold can be stored in a database or a configuration file. In some optional embodiments, the waterway can also be divided according to time periods, such as different speed thresholds during the day and at night. Alternatively, the sub-regions do not necessarily overlap in geography, but can partially overlap, each corresponding to different navigation rules.

[0097] Through the above scheme, the embodiment can set different speed thresholds according to the characteristics of different regions of the waterway, thereby improving the accuracy of the identification of abnormal behavior of ships entering and leaving the port and reducing the false positive rate.

[0098]

[0099] ​In a specific embodiment, on the basis of the above-mentioned embodiments, the method further comprises: first, before the step of judging whether the geographic locations of the current data point and the previous data point both fall within the geographic fence, the system determines the common sub-region of the channel according to the geographic locations of the current data point and the previous data point through a geographic space query. Specifically, the storage module has pre-stored the geographic fence coordinate set of the sub-regions of the channel, and the processor respectively takes the latitude and longitude coordinates of the current data point and the previous data point as input to perform a spatial inclusion query, i.e., to judge whether the coordinates fall within the geographic fence of a sub-region. If both data points only fall within the geographic fence of a unique sub-region, the sub-region is determined as their common attribution. If the two data points fall within the overlapping region of multiple sub-regions, the final attribution sub-region is determined according to the preset priority rules (for example, the priority of the sub-region close to the port is high). Then, the system calls the set of speed threshold values associated with the sub-region of the channel from the storage module for subsequent speed state judgment. For example, if it is determined that the current data point and the previous data point are both located in the "speed limit zone" of the channel entrance, the lower maximum speed threshold value corresponding to the region is called; if it is determined that they are both located in the "smooth zone" of the main channel, the higher maximum speed threshold value corresponding to the region is called, thereby realizing dynamic speed monitoring in different regions. In other optional embodiments, the geographic fence of the sub-region of the channel can be represented in different ways, for example, using a center point and a radius to represent a circular region, or using a grid map to represent an irregular region; the spatial inclusion query can be implemented by different algorithms, for example, the ray method, the radian method or the grid index method.

[0100] Through the above scheme, the present embodiment can dynamically adjust the speed threshold value according to the sub-region of the channel where the ship is located, more finely evaluate the speed state of the ship, improve the accuracy of the early warning, and reduce the false alarm rate.

[0101] In one specific implementation, based on the above embodiment, when the ground speed is detected to recover from the abnormal speed interval to the normal speed interval, the system first enters a delay judgment stage. Specifically, the system sets an observation window, which contains at least one subsequent AIS data point. Then, the system needs to determine whether the ground speed of all data points in the observation window continues to remain within the normal speed interval. For example, the system can configure the size of the observation window to be two consecutive AIS data points. Then, the system checks whether the ground speeds of the AIS data points at time T8 and T9 after the time T7 when the speed is detected to recover to normal are greater than or equal to the preset minimum speed threshold and less than or equal to the preset maximum speed threshold. Only when the speeds at time T8 and T9 both meet this condition, the system will generate an end signal indicating that the abnormal speed behavior starting at time T6 has ended. If at time T8, the speed meets the normal range, but at time T9, the speed falls back to the abnormal speed interval, the system will cancel the generation of the end signal and start monitoring again to avoid misjudgment. In other optional implementations, the size of the observation window can also be dynamically adjusted, for example, different window sizes can be set according to the type of the ship or the traffic density of the channel. In addition, the standard for "continuous retention" can also be more flexible, for example, a small amount (for example, 1) of short-term speed fluctuations within the observation window are allowed, as long as the overall trend is to remain within the normal speed interval, it can still be determined as "continuous retention".

[0102] Through the above scheme, the embodiment can effectively avoid misjudgment caused by AIS data fluctuation or ship speed fine-tuning, thereby improving the accuracy and reliability of the system in judging the end of the abnormal speed behavior.

[0103] In one specific implementation, based on the above embodiment, the method further comprises processing the boundary condition of the ship leaving the channel geographic fence. Specifically, when the processor judges that the geographic position of the previous data point is located within the channel geographic fence, and the geographic position of the current data point is located outside the geographic fence, the processor is configured to check whether there is an effective speed abnormal behavior associated with the target ship that has generated a warning signal but has not generated an end signal. If there is an effective speed abnormal behavior, the signal generation module generates an end signal to mark the complete life cycle of the abnormal behavior. In one specific implementation, the end signal can include an end reason field, the value of which is set to "leaving the channel" for subsequent event analysis and log recording.

[0104] In other optional implementations, in order to deal with the misjudgment caused by the drift of AIS data positioning near the boundary of the geographic fence, a buffer area can be set outside the geographic fence. When the geographic position of the previous data point is within the geofence, and the current data point is within the buffer zone, the same logic that generates the end signal is triggered.

[0105] With the above boundary processing scheme, the embodiment ensures that when the ship leaves the monitored water area, any active abnormal behavior event can be properly closed, thereby ensuring the logical integrity of the monitoring event life cycle and avoiding unnecessary continuous processing of ships that have left the monitoring range.

[0106] In a specific implementation, on the basis of the above embodiment, the waterway is pre-divided into multiple geographically non-overlapping sub-regions. This division is based on the actual physical conditions of the waterway and the navigation management needs. For example, the open water area at the entrance of the waterway can be divided into a sub-region, the narrow section within the waterway can be divided into another sub-region, and the turning area can be divided into a third sub-region.

[0107] For each sub-region, a set of independent speed thresholds and acceleration thresholds are maintained, which reflect the safety navigation requirements of the sub-region. For example, in open water, ships can travel at a higher speed, so a higher speed threshold and acceleration threshold can be set; while in narrow sections, ships need to travel at a lower speed and avoid sharp speed changes, so lower speed thresholds and acceleration thresholds are needed. These rule parameters associated with the sub-region are stored in the storage module and are associated with the corresponding geofence coordinates.

[0108] In other optional implementations, the sub-region division criteria can also be dynamically adjusted according to historical accident data, ship flow density, or hydro-meteorological conditions, etc. In addition, each sub-region can be associated with multiple sets of speed thresholds and acceleration thresholds, and can be switched according to different time periods or weather conditions to further improve the accuracy of identification.

[0109] With the above scheme, the embodiment can use different speed and acceleration thresholds for abnormal behavior identification according to the characteristics of different regions of the waterway, thereby more accurately reflecting the actual navigation risk of the ship and avoiding false positives and false negatives.

[0110] In a specific embodiment, on the basis of the above-mentioned embodiments, first, before judging whether the geographical positions of the current data point and the previous data point both fall within the geofence, the system determines the channel sub-region to which they both belong according to the latitude and longitude coordinates of the current data point and the previous data point. One method for determining the channel sub-region is to represent the geographical range of the channel sub-region as a polygon, and to use the algorithm for judging whether a point is within a polygon to judge whether the data point is located in a certain sub-region. If the current data point and the previous data point are both located within the polygon of the same sub-region, it is determined that they both belong to the sub-region.

[0111] Specifically, the system maintains a pre-configured mapping table of channel sub-regions and rule parameters, which is stored in the storage module 20. The mapping table takes the unique identifier of the channel sub-region as the key, and the corresponding value is the set of speed thresholds and the set of acceleration thresholds associated with the sub-region. Once the channel sub-region to which the current data point and the previous data point both belong is determined, the system retrieves the speed thresholds (including the minimum speed threshold and the maximum speed threshold) and the acceleration threshold associated with the sub-region from the mapping table. Then, the system will use these sub-region-specific thresholds for subsequent speed state judgment and speed change rate judgment, and then determine whether to generate a warning signal. In other optional embodiments, a machine learning-based classification model can also be used to automatically identify the channel sub-region in which the ship is located, which takes the latitude and longitude coordinates of the ship as input and outputs the channel sub-region to which the ship belongs.

[0112] Through the above scheme, the present embodiment can implement different speed and acceleration thresholds for different channel sub-regions, making the identification of abnormal behavior more refined and being able to adapt to the navigation characteristics of different segments, thereby improving the accuracy of the warning and reducing false positives.

[0113] In one specific implementation, on the basis of the above embodiment, the data acquisition module of the system is configured to specifically process AIS data streams from specific target vessels. First, the data acquisition module will filter and group all received AIS messages according to the vessel unique identification (MMSI, Maritime Mobile Service Identity) in the AIS message. Specifically, for each newly received AIS message, the data acquisition module will extract its MMSI and check whether the MMSI already exists in a "live vessel session list" maintained in memory. If it exists, the message will be added to the end of the AIS data stream corresponding to the MMSI. If it does not exist, a new AIS data stream will be created, and the MMSI will be added to the "live vessel session list", and then the message will be taken as the first data point of the data stream. Then, the data acquisition module will maintain the timestamp sequence of each AIS data stream to ensure that the AIS data points in each data stream are arranged in chronological order. Any out-of-order or duplicate data points will be filtered or corrected. Next, the system can configure a "session timeout" mechanism. If an AIS data stream of a vessel has not received new data for a period of time (e.g., 10 minutes), it is considered that the vessel has left the monitoring area or the AIS device has failed, and the corresponding AIS data stream is marked as "inactive" and removed from the "live vessel session list" to release system resources. This mechanism avoids long-term occupation of system resources due to long-term stationary of vessels or interruption of AIS signals.

[0114] Through the above scheme, the embodiment can ensure that the system processes continuous AIS data streams from the same vessel, thereby providing a reliable data basis for subsequent abnormal behavior identification of the vessel, and avoiding misjudgment due to confusion of data from different vessels.

[0115] In one specific implementation, on the basis of the above embodiment, when the system determines that a warning signal needs to be generated, the data acquisition module encapsulates the extracted timestamp, geographic position (longitude and latitude), ground speed, and type of abnormal speed interval in the current data point according to a predefined structured format. For example, the structured format can be JSON or XML. Specifically, an example of a JSON format warning signal is as follows: json { "timestamp": "2024-07-27T10:30:00Z", "longitude": 121.4737, "latitude": 31.2304, "sog": 3.5, "speed_exceedance_type": "below minimum speed" } The timestamp field records the time of the event, following the ISO 8601 standard; the longitude and latitude fields record the longitude and latitude coordinates of the ship, respectively, using the WGS 84 coordinate system; the sog field records the speed over ground of the ship, in knots; and the speed_exceedance_type field records the type of abnormal speed interval, which can be "below minimum speed" or "above maximum speed". The signal generation module then sends the JSON-formatted data to a designated destination, such as the API interface of the maritime supervision platform or a local log file. In other optional implementations, the warning signal can also use other structured data formats, such as XML, or a custom binary format to further reduce data volume. The type of abnormal speed interval can also be encoded with numbers instead of strings, such as 0 for "below minimum speed" and 1 for "above maximum speed".

[0116] Through the above scheme, the embodiment can provide a structured warning signal containing information such as time, location, speed, and abnormal type, which facilitates the maritime supervision department to quickly understand the detailed situation of the abnormal behavior of the ship and improves the efficiency of emergency response.

[0117] The embodiment of the application provides a ship speed abnormal behavior identification system for entering and leaving a port, as shown in the figure, which comprises a data acquisition module M100, a storage module M200, a processor M300 and a signal generation module M400, and is used for realizing the ship speed abnormal behavior identification system for entering and leaving a port in any of the above embodiments. Figure 5

[0118] The data acquisition module M100 is configured to obtain a series of time-ordered automatic identification system (AIS) data points containing the geographic position and speed over ground of the target ship. In one implementation, the data acquisition module M100 comprises a network interface capable of receiving AIS messages conforming to IEC 61162-1 and IEC 61993-2 standards. The data acquisition module M100 internally deploys a message parser that can extract the MMSI (ship unique identifier), timestamp, longitude and latitude coordinates, and speed over ground (SOG) from the received AIS messages. In other optional implementations, the data acquisition module M100 can be directly connected to an AIS receiver through a serial port, or can obtain data from a remote AIS base station through a wireless communication module (such as a 4G / 5G module).

[0119] ​The storage module M200 is configured to store geo-fences for defining ship lanes on a map and speed threshold values associated with the geo-fences. In one embodiment, the storage module M200 employs a PostgreSQL database and installs a PostGIS geographic information extension. The geo-fences are stored in the database in the form of polygons, each of which is composed of a series of latitude and longitude coordinate points. The speed threshold values are also stored in the database and associated with the corresponding geo-fences. These speed threshold values include a minimum speed threshold value and a maximum speed threshold value for defining a normal speed range. In other alternative embodiments, the storage module M200 can employ other types of databases (e.g., MySQL) or in-memory databases (e.g., Redis), and the geo-fences can be stored in other formats (e.g., GeoJSON).

[0120] The processor M300 is communicatively connected to the data collection module M100 and the storage module M200, and is configured to: select a current data point and a previous data point that are time-continuous in the sequence of AIS data points, and determine whether the geographic locations of the current data point and the previous data point both fall within a geo-fence stored in the storage module M200; in response to the geographic locations of the current data point and the previous data point both falling within the geo-fence, determine, based on a speed threshold value, whether the ground speed of the previous data point is in a normal speed range and whether the ground speed of the current data point is in an abnormal speed range. In one specific implementation, the processor M300 includes a geo-fence determination unit that uses a ray casting method to determine whether an AIS data point is located within a geo-fence. The processor M300 also includes a speed state determination unit that compares the ground speed of an AIS data point with the minimum speed threshold value and the maximum speed threshold value stored in the storage module M200 to determine whether the speed state of the data point is normal, too low, or too high. In other alternative embodiments, the processor M300 can use other types of geo-fence algorithms (e.g., point-in-polygon algorithm) or employ a hardware accelerator to improve the calculation speed.

[0121] The signal generation module M400 is communicatively connected to the processor M300 and is configured to generate a pre-warning signal indicating that the abnormal behavior of the ship speed occurs when the processor M300 determines that the ground speed of the previous data point is in the normal speed interval and the ground speed of the current data point is in the abnormal speed interval. In one example, the signal generation module M400 includes an alarm information generator that can encapsulate the pre-warning signal into an alarm sentence conforming to the NMEA 0183 protocol and send it to the VTS (vessel traffic management system) console through the serial port for display. The signal generation module M400 also includes an audible and visual alarm that will sound when an abnormal behavior is detected. In other optional embodiments, the signal generation module M400 can send the pre-warning signal to the remote monitoring center through the Ethernet interface, or send the alarm information to the designated personnel through the SMS gateway.

[0122] Through the above configuration, the data acquisition module M100 is responsible for continuously acquiring the AIS data of the ship, the storage module M200 provides the channel geographical information and speed rules, the processor M300 performs real-time analysis and judgment based on these information, and the signal generation module M400 is responsible for issuing a pre-warning when an abnormal behavior is detected. The modules work together to achieve automatic identification and pre-warning of abnormal behavior of the ship speed in and out of the port. This system architecture can solve the problem that the prior art cannot effectively identify the sudden change process of the ship speed from normal to abnormal, thereby realizing earlier and more accurate risk pre-warning.

[0123] Through the above scheme, the embodiment can monitor the ship speed in real time and timely issue a pre-warning when detecting an abnormal sudden change in the speed, thereby effectively improving the navigation safety guarantee capability of the port channel. Compared with the prior art, the embodiment has the beneficial effect that it can identify the "sudden change process" of the speed rather than only the "abnormal state", so that the pre-warning time is significantly advanced, providing sufficient time for timely intervention measures.

[0124] In a specific embodiment, on the basis of the above embodiment, the processor M300 is further configured to continuously acquire the ground speed of the subsequent AIS data points from the data acquisition module M100 after the signal generation module M400 generates the pre-warning signal, and repeatedly execute the logic of the speed state judgment. The processor M300 will determine whether the ground speed of each new AIS data point is still in the abnormal speed interval based on the speed threshold stored in the storage module M200. The signal generation module M400 is configured to generate an end signal indicating the end of the speed abnormal behavior only when the processor M300 detects that the ground speed recovers from the abnormal speed interval to the normal speed interval.

[0125] In one specific example, assume that the processor M300 detects a "sudden speed reduction" behavior of the ship at time Tl, and instructs the signal generation module M400 to generate a corresponding early warning signal. Thereafter, the processor M300 continues to receive and analyze the subsequent AIS data points. If the ground speed of the received AIS data points is still below the preset minimum speed threshold at time T2, the processor M300 does not take any action. Until time T3, the ground speed of the AIS data points received by the processor M300 is higher than the minimum speed threshold, indicating that the ship has resumed normal speed. At this time, the processor M300 instructs the signal generation module M400 to generate an end signal indicating the end of the speed abnormal behavior.

[0126] In other optional embodiments, the processor M300 can be configured to, after detecting that the ground speed has returned to the normal speed range, not immediately instruct the signal generation module M400 to generate an end signal, but to add a delay confirmation mechanism. For example, only after continuously receiving N (N is an integer greater than 1, such as 2, 3, or 5) AIS data points with ground speed higher than the minimum speed threshold, it is finally confirmed that the speed abnormal behavior has ended, and the corresponding end signal is generated. The delay confirmation mechanism can be implemented by a counter or a timer. The counter records the number of consecutive normal speed data points, and when the counter reaches the preset threshold N, the end signal is generated. The timer records the time when the speed returns to normal, and only when the time exceeds the preset delay time, the end signal is generated. The number N of the above delay confirmation can be configured through the storage module.

[0127] Through the above scheme, the embodiment can avoid misjudgment due to AIS data fluctuations or instantaneous adjustment of ship speed, and improve the accuracy and reliability of the end judgment of speed abnormal behavior.

[0128] In a specific embodiment, on the basis of the above-mentioned embodiments, the storage module M200 not only stores the channel geo-fence and the speed threshold, but also stores an acceleration threshold associated with the geo-fence. For example, in the PostgreSQL database, an "acceleration_threshold" field can be added to each channel record. The data type of this field can be float, with units of knots per minute, representing the maximum acceleration allowed for the channel. When determining whether the ship's speed is abnormal, the processor M300 first reads the acceleration threshold of the channel from the storage module M200, and calculates the speed change rate according to the current AIS data point and the previous AIS data point provided by the data acquisition module M100. The calculation method can be: (current speed - previous speed) / (current timestamp - previous timestamp). After obtaining the speed change rate, the processor M300 determines whether its absolute value is greater than the acceleration threshold obtained from the storage module M200. Only when the absolute value of the speed change rate is greater than the threshold and the conditions for the speed state transition are met, the signal generation module M400 generates a warning signal. In some other optional embodiments, the acceleration threshold can be stored in a separate configuration file or dynamically obtained from an external system through an API interface, rather than being directly stored in the database.

[0129] Through the above scheme, the present embodiment can effectively distinguish between "sudden" speed changes and "slow" speed changes of the ship, thereby improving the accuracy of the warning and reducing false positives.

[0130] In a specific embodiment, on the basis of the above-mentioned embodiments, the geo-fence stored in the storage module M200 is divided into a plurality of channel sub-regions. Each channel sub-region is associated with a set of independent speed threshold values, including but not limited to the minimum speed threshold value, the maximum speed threshold value. The division of the geo-fence can be based on the physical characteristics of the channel (for example, channel width, water depth, curvature) or traffic management strategies (for example, traffic control area, dangerous goods transportation area). The boundary of each channel sub-region is defined by a set of latitude and longitude coordinate points and stored in the storage module M200. The processor M300 first determines the channel sub-region to which the current data point and the previous data point belong according to the geographical positions of the current data point and the previous data point before determining whether the geographical positions of the current data point and the previous data point are both within the geo-fence. Specifically, the processor M300 uses the point-in-polygon algorithm to determine whether the current data point and the previous data point are both within the geo-fence of a specific channel sub-region. If the result is yes, the processor M300 calls the set of speed threshold values associated with the channel sub-region for subsequent speed state judgment. If the two data points belong to different channel sub-regions, the system can use a more refined interpolation algorithm to calculate a weighted average speed threshold value according to the distance weight, or directly ignore this judgment and wait until both data points enter the same sub-region before making a judgment.

[0131] Through the above scheme, the present embodiment can set different speed threshold values for different channel sub-regions, so that the identification of abnormal behavior of ships entering and leaving the port is more in line with the actual navigation environment, and the accuracy and reliability of the warning are improved.

[0132] The above is a further detailed description of the present application in combination with specific preferred embodiments, and the specific implementation of the present application cannot be limited to these descriptions. For ordinary skilled persons in the technical field to which the present application belongs, without departing from the concept of the present application, a number of simple deductions or substitutions can be made, which should be considered as falling within the scope of protection of the present application.

Claims

1. A method for identifying abnormal speed behavior of ships entering and leaving ports, characterized in that, include: Acquire a series of Automatic Identification System (AIS) data points sorted by time, including the target vessel's geographical location and speed over land; Based on pre-stored geofences used to define ship routes on a map and speed thresholds associated with the geofences; Select the current data point and the previous data point that are consecutive in time in the AIS data point sequence, and determine whether the geographical locations of the current data point and the previous data point both fall within the geofence; In response to the fact that the geographical locations of the current data point and the previous data point both fall within the geofence, based on the speed threshold, it is determined whether the ground speed of the previous data point is within the normal speed range and whether the ground speed of the current data point is within the abnormal speed range. When the ground speed of the previous data point is within the normal speed range and the ground speed of the current data point is within the abnormal speed range, a warning signal is generated to indicate that the ship has engaged in abnormal speed behavior.

2. The method according to claim 1, characterized in that, The abnormal speed range is defined as the ground speed being lower than a preset minimum speed threshold.

3. The method according to claim 1, characterized in that, The abnormal speed range is defined as the ground speed exceeding a preset maximum speed threshold.

4. The method according to claim 1, characterized in that, The method further includes: After generating the warning signal, the system continues to acquire and determine the ground speed of the subsequent AIS data points. When the ground speed is detected to have recovered from the abnormal speed range to the normal speed range, an end signal is generated to indicate the end of the abnormal speed behavior.

5. The method according to claim 1, characterized in that, The method further includes: After the step of determining whether the geographical locations of the current data point and the previous data point both fall within the geofence, if it is determined that the geographical location of the previous data point is outside the geofence while the geographical location of the current data point is inside the geofence, the step of generating the warning signal is not executed.

6. The method according to claim 1, characterized in that, The method further includes: Prior to the step of generating the warning signal, the method further includes: Based on a pre-stored acceleration threshold associated with the geofence, calculate the rate of change of speed between the current data point and the previous data point, and determine whether the absolute value of the rate of change of speed is greater than the acceleration threshold. The warning signal is generated when the absolute value of the rate of change of speed is greater than the acceleration threshold.

7. The method according to claim 6, characterized in that, The step of calculating the rate of change of speed includes: Extract the timestamps of the current data point and the previous data point respectively; Calculate the time difference based on the timestamp; The speed change rate is obtained by dividing the difference in ground speed between the current data point and the previous data point by the time difference.

8. The method according to claim 1, characterized in that, The pre-stored geofence is divided into multiple waterway sub-regions, and a set of speed thresholds is independently associated with each waterway sub-region.

9. The method according to claim 8, characterized in that, The method further includes: Before determining whether the geographical locations of the current data point and the previous data point both fall within the geofence, the waterway sub-region to which they belong is first determined based on the geographical locations of the current data point and the previous data point, and the set of speed thresholds associated with the waterway sub-region is called for subsequent determination.

10. A system for identifying abnormal speed behavior of ships entering and leaving ports, characterized in that, include: The data acquisition module is configured to acquire a series of Automatic Identification System (AIS) data points sorted by time, which include the target vessel's geographical location and speed over land. A storage module configured to store geofences used to define ship routes on a map and speed thresholds associated with the geofences; A processor, communicatively connected to the data acquisition module and the storage module, is configured to: Select the current data point and the previous data point that are consecutive in time in the AIS data point sequence, and determine whether the geographical locations of the current data point and the previous data point both fall within the geofence stored in the storage module; In response to the fact that the geographical locations of the current data point and the previous data point both fall within the geofence, based on the speed threshold, it is determined whether the ground speed of the previous data point is within the normal speed range and whether the ground speed of the current data point is within the abnormal speed range. A signal generation module, communicatively connected to the processor, is configured to: When the processor determines that the ground speed of the previous data point is within the normal speed range and the ground speed of the current data point is within the abnormal speed range, it generates a warning signal to indicate that the ship has engaged in abnormal speed behavior.

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