Quantitative Analysis of Uncertainty at the End of the Towed Cable in Underwater Towing Systems

In the ever-changing marine environment, the key to the optimal design of the towed cable and the precise control of the towed body in the underwater towing system is the quantification of uncertainty at the end of the towed cable. The Monte Carlo(MC) method, a traditional uncertainty quantification method, has high computation costs and low accuracy. In view of this, a method of uncertainty quantization at the end of a towed cable based on polynomial chaos(PC) was proposed. Latin hypercube sampling was used to obtain sample sets of the towed cable parameters, and the sample sets were substituted into the lumped-mass method model to obtain the coordinate of the end position of the towed cable. A proxy model of the end response of the towed cable was generated by the PC method, and the uncertainty of the end was quantified according to the characteristics of the orthogonal polynomials. At the same time, the results of the PC method were compared with those of the MC method. The results show that compared with the MC method, the PC method has a faster convergence speed in terms of sample size and higher accuracy. The uncertainty of motion response is approximately proportional to the axial length of the towed cable; the increase in cable length leads to the increase in uncertainty at the end, and the increasing trend is gradually flattened. When the uncertainty of the towed cable parameters is constant, increasing the speed of the mother ship helps to improve the stability of the towed body at height. The accuracy and efficiency of the PC method have been verified. Meanwhile, the quantitative analysis results of the uncertainty at the end of the towed cable guide engineering problems.