Chaojian Shi

Architecture of vision enhancement system for maritime search and rescue

Because of the limitation of physiological characteristics of human eyes, it is necessary to develop vision enhancement system for maritime search and rescue (SAR-VES), which is intended to improve the poor searching performance of human vision at sea. A system with its framework architecture, which integrate the imaging systems of visible light, infrared, radar and satellite remote sensing, is proposed in this paper to compensate the weakness of the human observation in the maritime search and rescue environment. The system will promote the sensitivity and the detection rate of targets, especially small ones, at sea. It will help improve the safety of life at sea and reduce economical losses in marine accidents.

Bringing Live AIS Information on the Web Sea Charts by Using Ajax

Besides collision avoidance and traffic monitoring, ship AIS (automatic identification system) information is very valuable in other fields of shipping industry. However, its very hard for people in these fields to access ship AIS information directly. To satisfy their demands, several live AIS Web systems have been developed. Most of them, however, could be further improved in the aspect of user friendliness. By using Ajax technology, we tried to develop a new live AIS Web system to publish the real time AIS information to the public. The architecture and several key technologies of the system, such as AIS information database construction and accessing, sea chart tiling and rendering, AIS information rendering and so on, are introduced. The system shows that Ajax can enable users to view AIS information smoothly. Compared to the legacy systems, more natural user interact behaviors are supported by this system.

An Algorithm for Interpolating Ship Motion Vectors

Interpolation of ship motion vectors is able to be used for estimating the lost ship Automatic Identification System (AIS) dynamic information, which is important for replaying marine accidents and for analysing marine traffic data. The previous methods can only interpolate ship’s position, while not including ships course and speed. In this paper, vector function is used to express the relationship between the ship’s time and space coordinates, and the tangent of the vector function and its change rate are able to express physical characteristics of ship’s course, speed and acceleration. The given AIS dynamic information can be applied to calculate the parameters of ships vector function and then the interpolation model for ship motion vectors is developed to estimate the lost ship dynamic information at any given moment. Experiment results show that the ship motion vector function is able to depict the characteristics of ship motions accurately and the model can estimate not only the ship’s position but also ship’s course and speed at any given moment with limited differences.

Harmonic Potential Field Method for Autonomous Ship Navigation

Autonomous ship navigation technology is a promising approach to reduce human errors in maritime accidents. Artificial Potential Field method has been successfully employed for path planning of autonomous mobile robot and it can also be effective for ship navigation at sea. The problem of local minima, however, should be properly tackled. Harmonic functions, by virtue of their extrema appearing only on the domain boundary, are novel approach for autonomous ship navigation. In this paper, harmonic functions are used in defining the potential field. A fluid dynamic analogy is introduced and proper boundary conditions are chosen to solve the navigation planning problem for ships. With harmonic potential field, ship navigation route can be generated automatically in constrained water areas and the tracks of the ships can follow the navigational regulations for the specific region as well. Computer simulations are conducted for two typical water areas such as Traffic Separation Scheme and narrow channel. The simulations illustrate satisfied results for path planning of ship navigation.

Recognizing road environment for vision system on autonomous vehicles

A road environment recognition system is presented. First, lane lines are detected based on our proposed Gaussian comparison function. Then a road prospective model is built on the basis of a new Gaussian semi-sphere approach to detect vanishing point. Using this model, three road parameters are computed, i.e. vehicles transverse bias, yawing angle and the road slope angle. Obstacles such as vehicles in front of the current lane are also extracted. Simulation experiments prove the effectiveness of the system.

Active Vessel Navigation Monitoring with Multi-media Message Service

Many online vessel monitoring services have been developed, and most of them, however, are available only when a user is logging on them. A notification service that can send vessel navigation messages to offline subscribers was developed in this paper. Therefore an active vessel navigation monitoring service is implemented. Each message contains a background image and a mark showing a vessel’s position and navigation status, which are derived from AIS reports. The background image is selected from the existing map tile databases based on the position of the vessel. More than one image may be selected, so a RBF network with two inputs, image information entropy and scrambling degree, is built to choose the proper background image. Experiments show the RBF network has a correct rate of 84%. The active vessel navigation monitoring service developed in this paper shall be helpful for the business of the offline users.

PortLive: A Bridge to Ship AIS Information Island

Besides collision avoidance and traffic monitoring, ship AIS (Automatic Identification System) information is very valuable in other fields of the shipping and logistics industry. However, its very hard for most people in these fields to access ship AIS information directly due to high expenses. To break down the AIS information isolation, several live AIS Web systems have been developed. Most of them, however, could be further improved in the aspect of user friendliness. This paper tries to develop a new live AIS Web system, namely PortLive, to build a bridge to the ship AIS Information Island for the public. The potential applications of ship AIS information in the shipping and logistics industry as well as the main functions, the architecture and several key technologies of the system are presented in this paper. Through PortLive, users are directly accessible to the real time and historical AIS information overlaid on nautical charts, or receive multi-media notifications in a passive way. Compared to the relevant systems, better user friendliness is provided by this system.

Vessel Collision Avoidance in Close-Quarter Situation Using Differential Games

In solving collision avoidance problem of two vessels in close-quarter situation, differential game theory is introduced to investigate anti-collision strategy in close-quarter situations. Mathematical model using differential game theory for collision avoidance is formulated. The collision avoidance problem in urgent situation is converted into differential games problem. By differential games method, the optimal controlling strategies for the two vessels are deducted from the mathematical model. Numerical simulation of various meeting situations is performed. The research indicates that the controlling strategy is optimal when they have the same acceleration direction. It is also shown that difFerential game theory is an effective tool in dealing with collision avoidance problems.

Real-time Risk Assessment for Aids to Navigation Using Fuzzy-FSA on Three-Dimensional Simulation System

The risk level of the Aids to Navigation (AtoNs) can reflect the ship navigation safety level in the channel to some extent. In order to appreciate the risk level of the aids to navigation (AtoNs) in a navigation channel and to provide some decision‐making suggestions for the AtoNs Maintenance and Management Department, the risk assessment index system of the AtoNs was built considering the advanced experience of IALA. Under the Formal Safety Assessment (FSA) frame, taking the advantages of the fuzzy comprehensive evaluation method, the fuzzy‐FSA model of risk assessment for aids to navigation was established. The model was implemented for the assessment of aids to navigation in Shanghai area based on the aids to navigation three‐dimensional simulation system. The real‐time data were extracted from the existing information system of aids to navigation, and the real‐time risk assessment for aids to navigation of the chosen channel was performed on platform of the three‐dimensional simulation system, with the risk assessment software. Specifically, the deep‐water channel of the Yangtze River estuary was taken as an example to illustrate the general assessment procedure. The method proposed presents practical significance and application prospect on the maintenance and management of the aids to navigation.

Automated Collision Resolution for Vessel Traffic Management by Using Cooperative Multi-Agent Negotiation

One of the most important functions of VTS is to resolve collision among vessels by giving anti-collision advice. In the past, the advice was generated by manual ARPA plotting which may lead to heavy workload. Recently, AIS are widely deployed on vessels. Therefore, VTS can collect more accurate data about the movement of the vessels than before. That makes it possible to generate anti-collision advice automatically. In this research, we built a cooperative multi-agent negotiation system to generate anti-collision instructions for VTS operators. This system can create a software agent for each vessel, constantly monitors their movement, detects the collision risk, and initiates a negotiation process if collision risk exists. Agents negotiate with each other complying with monotonic concession protocol to make themselves more and more concessive until an agreement is achieved. Simulation results show that this system can generate safe and economic anti-collision instructions for VTS operators, and the application of this research shall improve the efficiency of VTSs.