Research And Simulation Of Ship Track Control Algorithm

Autopilot is an important control equipment, with two kinds of automatic controlmode: heading control and track control. With the increasing perfection of the controltheory and the continuous development of science and technology, people have a higherrequest on automatic pilot and need study out more efficient, economic and securitytrack control algorithm. Keeping up with development trend of ship motion controlalgorithm, enhancing stability, security and economy of ship navigation, this papercombined with the new guidance algorithm and optimal heading control algorithm todesign a kind of economical and practical track control algorithm, for the research targetthat high control precision, strong anti-jamming capability and less number of steering,to contribute strength in improving the track control level.Firstly, study a modeling method of ship motion mathematical model. In order toobtain more reliable test data of tracking control algorithm, according to ship modelingmethod of IEC62065, this paper research on ship propulsion, steering gear, surge model,sway model and yaw model, and then establish the mathematical model of wave andcurrent on the basic of analyzing environmental factors in ship navigation. This paperalso presents a simple and practical method of dead reckoning that can accuratelysimulate the changes of ship position. Through the ship turning simulation experiment,it is clear that ship modeling method has higher simulation accuracy and can be usedfor simulation research of ship track control algorithm.Secondly, study the ship track guidance algorithm. Guidance algorithm mainlyincludes track calculation, linear guidance and curve guidance in this paper. For trackcalculation, this paper does studies on method of calculation for ship navigationdeviation, and put forward a new practical method to calculate navigation deviationwith great-circle track. For linear guidance, based on smooth asymptotic properties ofhyperbolic tangent function, this paper proposes a new hyperbolic guidance methodwhich can improve the ship tracking rate and avoid position overshoot. For curveguidance, based on Lyapunov stability function, this paper presents a reverse steppingcalculation method to calculate heading rate command to make the system globallyasymptotically stable, and gives a correction formula for current interference.Again, study the ship course control algorithm. Combining with the feedbacklinearization algorithm and the optimal control algorithm, this paper innovatively putforward the feedback linearization optimal heading control algorithm in view ofnonlinear ship model. This algorithm is a comprehensive algorithm which can not onlycontrol the ship heading but also control the ship steering rate, so the space complexityof the program can be effectively reduced. In view of the nonlinear model and waveinterference model of the ship, this paper design a kind of extended state observer andgive the formula of feedback gain matrix to solve the problem of wave interferencecaused by the frequent steering. According to the test results of various types of ships,this control algorithm has the advantages of strong anti-jamming capability, fewersteering number and small steering amplitude. Finally, study and design of ship motion control simulation system. From the angleof improving efficiency and on the basis of the mixed programming skills of Matlaband VC++, this paper designs a stand-alone and non-real time simulation system on themodel of a real control environment. The simulation system consists of track controller,steering engine actuator, steering engine feedback mechanism, ship motion simulatorand ECDIS. The simulation time of the simulation system is about0.01times real time.It can effectively improve the efficiency of simulation. ECDIS who has the friendlyinterface and simple operation provides visual information for the simulation test andcan quickly analyze the properties of the tracking control algorithm.By the application of ship motion control simulation system, this paper does the testperformances of track control algorithm from different scenarios and then obtains: trackcontrol algorithm of this paper has high control precision, strong anti-interferenceability, less number of steering control and achieves the expected goals.