Research on Intelligent Avoidance Method of Shipwreck Based on Bigdata Analysis

Abstract In order to solve the problem that current avoidance method of shipwreck has the problem of low success rate of avoidance, this paper proposes a method of intelligent avoidance of shipwreck based on big data analysis. Firstly,our method used big data analysis to calculate the safe distance of approach of ship under the head-on situation, the crossing situation and the overtaking situation.On this basis, by calculating the risk-degree of collision of ships,our research determined the degree of immediate danger of ships.Finally, we calculated the three kinds of evaluation function of ship navigation, and used genetic algorithm to realize the intelligent avoidance of shipwreck.Experimental result shows that compared the proposed method with the traditional method in two in a recent meeting when the distance to closest point of approach between two ships is 0.13nmile, they can effectively evade.The success rate of avoidance is high.


INTRODUCTION
Ships at sea will encounter. Many factors such as the bad weather or the low visibility, the ship driver's dereliction of duty without using the safety speed, the risk judgment errors, or the improper avoidance operation [1][2]can cause the ship into the close quarters situation, even forming urgent danger [3][4]. More than 80% of the maritime accidents are owing to human factors [5][6].Most of them are caused by violating International Regulations for Preventing Collisions at Sea and the driver's carelessness [7][8]. In order to alleviate the human error factors in the process of ship avoidance and fundamentally reduce the shipwreck caused by human decision-making errors, we need to research the intelligent avoidance methods for ship shipwreck [9]. The reference [10][11][12] proposes the method for avoiding maritime accidents based on big data for scientific decision. Through the cluster analysis of sailing factors of ship accident and association rules mining for all kinds of accident factors, we can realize the intelligent avoidance of shipwreck, but this method has a series of problems that the recognition accuracy of ship collision avoidance is low, the probability of successful avoidance is low,and the feasibility of avoidance decision is poor. Therefore, a method of intelligent avoidance of ship collision based on big data analysis is proposed [13][14][15][16][17].

CALCULATION OF DISTANCE TO SAFE POINT OF APPROACH OF SHIP BASED ON BIGDATA ANALYSIS
Using the big data analysis to calculate the ship safe distance of approach under the head-on situation, the crossing situation, the overtaking situation. The specific process is as follows: The ship safe distance of approach (SDA) is mainly determined by the radius of the collision region (SDAmin), the room for manipulation of the ship and the encountering characteristics of ship. Because the radius of ship collision region (SDAmin) is centered on this ship,the size of two ships, the circular area of the ship encountered situation will be considered,and the collision will occur when two ships enter the area. The radius of ship collision zone is calculated by big data analysis. Its formula is: Among them, 0 L and t L respectively indicate the length of our ship and the target ship; P indicates GPS positioning accuracy of the ship [18].
Considering the intersection relation between position of ship and our ship, different distance of the safe point of approach (SDA) models of ships are obtained, and the formula is as follows: In the formula, Adm and Trm respectively represent the longitudinal distance of ship gyration and the horizontal distance of the ship gyration. t represents the time required that the small rudder angle of this ship changes to the new heading distance; t v represents the real speed of the target ship sailing. According to the formula (2), when the target ship is overtaken by our ship, formula (3) holds; when the target ship is the overtaking ship or it is placed in (122. , thus, formula (1) is workable; otherwise, formula (4) is workable.
Among them, in formula (2): In the formula, r v represents the speed of relative motion of ship sailing; r c represents course of relative motion of ship sailing; V represents speed of ship sailing; K represents turning index of ship sailing; T represents the turning lag index of ship; 0 represents the current rudder angle in ship sailing; 0 represents the current redirection angle in the ship sailing; R represents turning radius of ship sailing; 1 t represents the time required from the steering rudder angle to the current rudder angle 0 in the ship sailing.
Thus, when head-on situation and overtaking situation happen in ship channel, the calculation formulas of the ship safe distance of approach are as follows: In the formula, 1 B and 2 B represent the ship beam of two ships respectively; and represent drift angles of two ships; max B represents the ship beam of the bigger one in two ships.

CALCULATION OF RISK DEGREE OF SHIP COLLISION BASED ON BIGDATA ANALYSIS
According to the calculation results of safe distance of approach of ships, we use the big data analysis to judge the risk degree of collision of ships, and calculate the minimum value and maximum value of time of last minute action in dangerous situation of ships collision and the different value ranges of ship initial time of last minute action to judge the degree of risk degree ships collision and danger level. The detailed steps are described below: According to the big data analysis, usually the small rudder angle of ship sailing is 10 o . The maximum rudder angle is 30 o . Generally, the redirection angle of ship is 1 C , and the maximum redirection angle of ship is 3 C . According to the geometrical analysis of relative motion in the ship sailing, the PIDVCA theory establishes the model for solving the target ship motion element and predicting movement element after our ship changes direction, and calculates the equations of the straight line RML and the straight line NRML respectively.
In the formula, r C and rn C represent the course of our ship and the course of the target ship relative to our ship before and after the redirection. According to the formula (9), the coordinates of the intersection point b of two straight lines are calculated. Its expression is: When our ship and target ship encounter, assuming that our ship turns right to m C , and the sailing relative displacement generated by ships is expressed as SS . The components of the horizontal axis and the vertical axis are expressed as S X and S Y , and its calculation formula is as follows: Among them, Tn shows that the time required for cycle that our ship turns to 90 o at full speed and full rudder; Dc represents the tactical diameter of ships; Fd represents the cyclic advance distance of ships. The formula of relative displacement SS of sailing generated by ships is as follows: The point a is taken from the straight line RML , which makes the length of ab equal to the relative displacement of the ship which is generated by the ship. a is used as the estimated helm point of our ship when it is sailing. We can derive the coordinate of estimated rudder point a of the ship at this time: sin Thus,the calculation formula of maximum critical distance max Did of the ship imminent danger is as follows: The time from the current moment ( , ) C x y to estimated helm point ( , ) a a a x y is the helm time of ships. Its expression is: a a a x y is corresponding to the coordinate of initial rudder distance of ship, the calculation result in above formula (15) is the initial rudder time of ship a a a x y is corresponding to the distance DE of close quarters situation of ship collision, the calculation result in above formula (15) is the last helm time (1) when 1 ln( , ) 3min T SDA C , if the sailing ship uses its minimum rudder angle and the minimum redirection angle to pass the safe distance of approach, the time is relatively abundant and it is a potential danger ( 1) ek of ship collision; (2) when 1 ln( , ) 3min T SDA C and 3 ln( , ) 0 T SDA C , when the navigating ship uses its minimum rudder angle and the minimum redirection angle is close to the time of passing the safe distance of approach SDA , which is a common danger , the sailing shipis unable to travel from the minimum safe distance min SDA of approach, namely, it is unable to avoid the collision,which belongs tothe imminent danger of ship collision ( 4) ek .

INTELLIGENT AVOIDANCE OF SHIPWRECK BASED ON GENETIC ALGORITHM
On the basis of the judgment of risk degree of ship collision, three evaluation functions of ship sailing are calculated, and the intelligent avoidance of shipwreck is realized by genetic algorithm. Specific practices are as follows: Firstly,we determine the target ship which has the maximum risk of collision with our ship on each ship route at sea,and calculate difference between the minimum distance and safe distance in the target ship and our ship to determine the security of our ship route. Thus, the computational expression of the safety evaluation function of navigation: Among them, x is the chromosome, which represents a route of ship; i represents the node of a path on this route. i is from 1 to 1 N . N represents the total number of genetic factors of a path on the route (i.e. the turning point or node), there are 1 N short ship routes. Thus: In the formula, represents the safe distance of approach of ships; k and h represent the evaluation coefficient of security; i g represents the minimum of distance between the target ship which has maximum risk degree of ship collision the during the sailing, when our ship route is between the i-th node and the 1 i -th node in all target ships which are detected.
The economic evaluation function of ship sailing is calculated. The economic evaluation of ship sailing mainly includes the consumption of ship route in various aspects, such as the degree of smoothing of ship route, the voyage consumption of ships, the time consumption, and other parameters. The calculation formula is as follows: Among them, d w , t w and s w represent the coefficient factor of economic evaluation function of ship sailing; The evaluation function of traffic rules for ship sailing at sea is calculated. The formula is: In the formula, _ Cos ( ) i T t x represents the degree that ships abide International Regulations for Preventing Collisions at Sea.
According to the three evaluation functions mentioned above, supposing that the course of our ship and the target ship j is expressed as O and Tj , and the steering avoidance of ship is analyzed. The specific process is as follows: 1. if board angle Tj of the target ship j which has the maximum risk degree of ship collision relative to this ship is: , It shows that when our ship and the target ship j form the head-on situation on the voyage, we can judge that our ship is the ship which avoids the pass-by ship or has the same circumvention responsibility, and we should take the action of turning right: indicates that the ship is the crossing situation of larboard angle. According to International Regulations for Preventing Collisions at Sea, the ship can be judged as the direct route. The target ship which has maximum risk degree of collision gets out of the road. If our ship takes evasive action, which is inconsistent with the rules. 4)when our ship is overtaking the target ship, our ship is a given-way ship. because of the true bearing of our ship is O a relative to the target ship, but our ship has not taken evasive action, which is inconsistent with the rules. Thus, the intelligent avoidance of shipwreck has been realized.

EXPERIMENTAL RESULTS AND ANALYSIS
Experiment usesVisual Basic8.0 as development platform, and usesthe big data analysis software and genetic algorithm to simulate the intelligent avoidance process of shipwreck,in order to test the effectiveness and feasibility of the proposed method.
At the initial time, the sailing speed of the target ship 1 is 12 kn, and the sailing direction is 302.8 o . The sailing speed of the target ship 2 is 15 Kn, and the sailing direction is 152.7 o . The two ships in the voyage are 0.37nmile apart, 0.04 DCPA nmile , 1.23 TCPA nmile , min 0.056 SDA nmile . According to the calculation of risk degree of ship collision, two ships have formed the immediate danger situation. We use the method proposed in this paper to carry out the intelligent evasive action of shipwreck. The experimental test result is shown in Figure 1. According to Figure 1 (a), we can see that the collision avoidance of two ships is successful. Evasive parameters in the whole process of ship collision avoidance are analyzed, as shown in Figure  1 (b) &(c). DCPA is increased from 0.02 nmile to 0.06, and the ship will pass through outside of min SDZ .At this time, the ship TCPA will gradually change from 1.73 to -0.67, which shows that the ship has passed the distance to closest point of approach.  nmile . According to the calculation of risk degree of ship collision, two ships have formed the immediate danger situation. We use the method proposed in this paper to carry out the intelligent evasive action of shipwreck. According to Figure 2 (a), we can see that the collision avoidance of two ships is successful. Evasive parameters in the whole process of ship collision avoidance are analyzed, as shown in Figure 2 (b) &(c). DCPA is increased from -0.028nmile to -0.16, and the ship will pass through outside of min SDZ .At this time, the ship TCPA will gradually change from 2.3 to -0.3, which shows that the ship has passed the distance to closest point of approach.
(a)Two Ships Run Safely Evading Each Other  Figure 3 (a), we can see that collision avoidance of two ships is successful. Evasive parameters in the whole process of ship collision avoidance are analyzed, as shown in Figure 3 (b) &(c). DCPA is increased from 0.0013nmile to 0.055, and the ship will pass through outside of min SDZ .At this time, the ship TCPA will gradually change from 1.62 to -0.21, which shows that the ship has passed the distance to closest point of approach, and DCPA is nmile. At this time, DCPA is not more than min SDZ , this is because two ships belong to the crossing encounter. According to the calculation of proposed method we can see that the two ships still can successfully realize collision avoidance. According to the calculation of risk degree of ship collision, two ships have formed the immediate danger situation. We use the method proposed in this paper to carry out the intelligent evasive action of shipwreck. According to Figure  4 (a), we can see that the collision avoidance of two ships is successful. Evasive parameters in the whole process of ship collision avoidance are analyzed, as shown in Figure 4 (b) &(c). DCPA is increased from 0.01nmile to 0.16, and the ship will pass through outside of min SDZ .At this time, the ship TCPA will gradually change from 2.32 to -0.38, which shows that the ship has passed the distance to closest point of approach, and DCPA is nmile. This also shows that two ships in the closest point of approach are 0.13 nmile apart,which can achieve successful avoidance.
(a)Two Ships Run Safely Evading Each Other

. Effect Diagram of Intelligent Avoidance Simulation of Shipwreck Based on Big Data Analysis
According to the analysis of above simulation test results, when the ship is sailing in the immediate and dangerous situation,the method proposed in this paper can realize the intelligent avoidance of shipwreck.

CONCLUSION AND DISCUSSION
The method proposed in this paper analyzes the basic principle for avoiding shipwreck and the corresponding mathematical model of ship motion on the basis of previous research, and builds intelligent method for avoiding shipwreck based on big data analysis, combined with the mathematical model of ship motion, we carry out the simulation experiment based on the full analysis of genetic algorithm. The main research results are as follows: (1) select a reasonable genetic code structure, and reasonably indicate the intelligent avoidance ship route of shipwreck.
(2) the method proposed in this paper considers the safety and economic performance of ships, and also takes into account the cases of observing International Regulations for Preventing Collisions at Sea.
(3) three operations such as the selection, crossover and mutation are used, and the way of parallel operation is used to realize the intelligent avoidance of shipwreck.
(4) this paper has fully analyzed the different situations that ship encounters, and makes a correct judgment according to the dangerous degree of the close quarters situation of ship so as to realize the intelligent and safe avoidance of shipwreck.
(5) but the intelligent avoidance method of shipwreck realizes the avoidance only through the ship altering, which does not take into account the ship slowdown.Usually, in port water area, especially the junction of many sea-routes, more often, the ships achieve collision avoidance bythe way of slowdown, which shows that the proposed method remains to be study on in depth.