Research On Thrust Allocation Optimization Algorithm Of Semi-submersible Drilling Platform

As the development of oil exploration to deeper ocean, the traditional mooring positioning system for ocean engineering system could not meet new requirements of normal operation for drilling platform. Due to its independence on depth of water, accurate and fast positioning and convenient operation, dynamic positioning system(DPS) becomes a key technology to solve the problem of deep-sea oil exploitation. Thrust allocation system is an important part of the DPS. The total force generalized by thrusters should counteract environment interferences and the power consumption of the system is minimized.Focusing on the "Offshore Oil 981" with eight azimuth thrusters, the intelligent optimization technology of thrust allocation is studied based on a hybrid optimization algorithm which combines the simulated annealing(SA) algorithm and particle swarm optimization(PSO) algorithm. The main contributions are as follows:1. The mathematic model is established based on the analysis of the movement principles of semi-submersible drilling platform, and also the calculation models of external forces such as wind, wave, and ocean current are given. Then simulations are presented to show the correctness of the mathematic model.2. Based on the analysis of the thrust allocation system, mathematic model of thrust allocation is established according to the characteristics and layout of thrusters.3. A hybrid algorithm is proposed combing PSO with SA, which can effectively solve the problem of running into local extremum easily for PSO, and benchmark functions are used to demonstrate the effectiveness of the hybrid algorithm.4. The hybrid optimization algorithm is used for the thrust allocation based on dynamic optimization region. The objective function is modified by introducing the penalty term adaptive weight, and therefore the dynamic performance of thrust generated by thrusters meeting control command is improved.5. The simulation model of the thrust allocation is designed for semi-submersible drilling platform based on Matlab/Simulink, and then simulations are provided to demo- nstrate its effectiveness for the DP system in different oceanic conditions.Finally, research work presented in the thesis has been concluded comprehensively and further research aspect is pointed out.