| The ocean has become the focus of the development and utilization because of the increasingly rich marine resources in recent years.It is known that when a ship sailing in the sea,it will occur rocking motion in all directions due to the disturbance of wind,wave,and flow.Offshore operations can not be conducted stable and reliable as a result of a lot of swing.The topic about how to make the ship at a predetermined position remains substantially has become a research hotspot in recent years.As it is impossible to spend a lot of human and financial resources to do the real boat experiment,the laboratory developed a ship position motion control platform based on ship sway,vertical swing and yawing three degrees of freedom to research the ship positioning.In hardware design, the experimental platform includes four tracks.The down two layers are used to simulate the wave action and the top two layers are used to simulate the ship motion.The stepper motor is the actuator of the whole system. As the core of the whole system, two PC104machines use the8253timer to generate two groups of pulses as the enable and direction signals to control wave platform and ship platform separately.In addition,we use the laser distance sensor to complete closed-loop control system via RS232serial interface.In algorithm design,the basic principles of Backstepping and traditional PID control algorithm and their application in ship control platform are mainly described by the article.The recursive design idea is applied by the Backstepping control algorithm.It also combine with the Lyapunov stability theory to design the Lyapunov function in each step of the derivation until the system control input appears.Then we do the pure Matlab simulation alone and semi-physical simulation for Backstepping control algorithm.At the same time,the PID control algorithm is applied to do the semi-physical simulation From the experiment results,PID control algorithm is slightly better than Backstepping control algorithm. |
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