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In this paper, an expectation maximization based sequential modified unbiased converted measurement Kalman filter is proposed for target tracking with an unknown correlation coefficient of measurement noise between the range and the range rate. Firstly, a pseudo measurement is constructed by multiplying the range and the range rate to reduce the strong nonlinearity between the measurement and the target state. The mean and covariance of converted errors are subsequentlsubsequently derived by modified unbiased converted measurement to weaken the error caused by the linearization of the measurement equation, which is effectively to improve the dynamic accuracy of target tracking. Then, the converted errors of the position and the pseudo measurement are decorrelated by the Cholesky factorization and thus to obtain the posterior probability distribution of the state by using the sequential filtering in the Bayesian framework. Finally, the expectation maximization is introduced in the updating procedure of the pseudo measurement to jointly estimate the target state and the correlation coefficient. The target tracking scenario with an unknown correlation coefficient is built to demonstrate the validness and feasibility of the proposed algorithm. Simultaneously, the results of the normalized error squared validate the consistency of the modified unbiased converted measurement.

In the case of satisfactory waterway condition, the scale of the port area affects the tonnage and size of the vessels operated in the port directly, which leads to a higher demand on the tugboat configuration in the port. In this article, a simulation model of the operation system of ships entering and leaving the port is established based on the computer simulation technology to study the optimal quantity of tugboats required in the different handling capacity condition of the port. The result of the study shows that, in a certain range, the demand of the tugboats is increasing with the development of port handling capacity. However, when the handling capacity reaches a certain value, the increase of the tugboats number do not have a significantly effect on the improvement of port handling capacity.