Advantages and Disadvantages of Different Solvers for Preliminary DP Capability and Operability Predictions

With the constant movement of DP operations through deep water areas, nowadays the DP system is installed on all kinds of offshore units. Therefore, it is of utmost importance to predict the DP system’s capability since the early stages of the design. In this stage, it is impossible to perform accurate time domain simulations as many vessel and system parameters are unknown. Then, it is only possible to perform quasi-static simulations to perform capability and operability predictions. In the literature, plenty of methods are suitable for executing a quasi-static calculation, employing different algorithms for the problem of thrust allocation. The thrust allocation problem has straightforward resolutions, up to complex and sophisticated options based on differential evolution algorithms. Besides the definition of the thrust allocation algorithm, there is a problem associated with the environmental loads. Also in this case the representations are multiple and can cause a problem in interpreting the capability and operability predictions. The present work compares different resolution methods for the thrust allocation procedure by keeping the estimation process for the environmental loads constant. The results presented for a reference vessel highlight the peculiarities and abilities of each type of thrust allocation solution, providing insight to an offshore designer in selecting the proper tool for their preliminary predictions.