Research On Course-keeping Control For Ships By Wireless Network

In order to meet the development needs of ship control system,a variety of intelligent terminals and sensors are applied in the ship.If these devices are connected through wired network,their flexibility and mobility will be restricted.Besides,some problems exist when wired network are used in the ship.To solve the above problems,ship wireless sensor network emerges with the mobility,flexibility,expansibility,low cost and convenient maintenance.It can achieve the on-demand deployment of various intelligent terminals and sensors and effectively solve the difficulties in ship wiring and fitting because of the confined space.Recently,the wireless sensor network has mainly applied to ship monitoring,communication,and positioning,etc.This thesis designs wireless sensor network as redundant network of ship steering control system and studies the ship course-keeping control based on the wireless network.The major research contents and methods are stated as follows.Firstly,in view of limited energy and real-time communication of the wireless sensor network,an operating system called Mindows was established,in which sensor node with low power consumption was devised and a power management solution of the node including microprocessor,peripheral devices and battery power was proposed.The test results have proved that the operating system runs steadily and the solution can reduce the power consumption of the node and extend the life cycle of wireless sensor network.Secondly,in order to meet the needs of research on ship course-keeping control by wireless network and implement the simulation experiment of the proposed algorithm,the offshore or river ship course-keeping control test platform based on GPRS and ZigBee network is established by the Visual Basic programming language,which remedies the limitations of the single digital simulation.The experimental results have verified the feasibility of ship course-keeping control through remote and local wireless networks in the platform.The practicability of platform are also illustrated.Thirdly,to deal with the long time-delay and nonlinearity of the ship motion in sea,a concise robust control algorithm based on the gray prediction method is proposed,which adopts improved gray model to predict the error of ship course in time and applies the predictive value to the concise robust controller.A simulation is carried out.The results have shown that the algorithm possesses simple form and good robustness and the parameters are easily set in the algorithm.Finally,to solve the problems of redundant wired networks in ships,the thesis designs the ZigBee wireless sensor network as a redundant network for the ship steering control system.In view of the wireless network control system(WiNCS)problems,the co-design of a communication protocol and control algorithm is studied in the thesis.From the aspect of communication,the design is based on the concurrent and disjoint multipath routing ZigBee network,which can ensure the effective application of the control algorithm.From the aspect of control,the design of the ship course-keeping controller combines an improved gray model with the nonlinear robust controller based on the nonlinear decoration and integrator backstepping method,which can compensate for time delay and packet loss.The simulation is conducted and its results have proved that the scheme can optimize the overall performance of wireless network control and yield better control effects,which has some reference value in practical application.In conclusion,the experimental results prove that the application of the wireless network control to the ship course-keeping control is feasible and effective on a simulation platform,which is a beneficial attempt.As the technologies of wireless networks develop and improve constantly,the ship steering control system adopting wireless network to replace wired network will become a trend in the future.