| The deep sea contains abundant mineral resources. The mining vessel is the important equipment of the deep sea mining, a mining vessel is controlled in the offshore position through a dynamic positioning system, The dynamic positioning system consists of several thruster. A mining vessels are exposed to wind, waves, and currents at sea, once the thruster fails, safety accidents of uncontrolled motion are very likely to occur. This paper studies the dynamic positioning performance of thrusters and analyzes the loss of dynamic positioning function of thrusters in different failure modes. The wave load based on the hydrodynamic theory was calculated. The thrust was optimized with the PID method .The time domain motion response of the single thruster failure and multiple thruster failure conditions at different positions of the deep−sea miner was numerically simulated. The influence of various failure conditions on the three degrees of freedom motion of the deep−sea mining vessel, namely, sway, sway and yaw, was compared, and the influence of each failure condition on the thrust of the remaining thrusters was analyzed. The research shows that, as the unloaded and 90°wave direction, The effect of different failure modes of thrusters on surge motion is far less than that on sway and yaw motion, the effect of single thruster failure at stern on dynamic positioning of surge and yaw motion is more than effects of two thruster failure. The failure of two thrusters has greater impact than that of single thruster for dynamic positioning of mining ship with multiple degrees of freedom. Two thrusters on the same side or two thrusters at two side are failed at same time, it is same for influence on dynamic positioning, and has the greatest impact on sway motion. This article reveals that Effect degree and mechanism of thruster failure on the motion of deep−sea mining vessels, and it has guiding significant for operation safety of deep−sea mining vessel. |
