A comparison of characteristic locus and optimal designs for dynamic ship positioning systems

Dynamic ship positioning systems are now required to operate within closer position tolerances and in more adverse weather conditions. There are also stricter requirements on the minimization of energy losses. To optimize performance, recent positioning systems have been designed using Kalman filters and optimal control theory and such a scheme is reviewed briefly. The characteristic locus design method has not previously been used for the design of a stochastic system and it is therefore of interest to see whether or not it may be employed in the above problem. It is shown that not only may this frequency domain design method be used for such systems, but that it has some advantages with regard to the flexibility of the design process. The advantages of using a Kalman filter together with controllers designed by this approach are also demonstrated.