Conventional control theory is based on input-output relationship. Generally it is not called optimal control system. It is possible to design the optimal control system by modern control theory using the state space method. However,state space method is required precise mathematical representation for dynamic characteristics of the initial conditions. Also,it may not be possible to measure the state variables by a feedback control input as ship's autopilots. In this case,estimate the state variables using the state observer.
Ship's autopilots are mainly using TK model. In this papter,we described the state observer design method using TK model and the state estimation result