A new position controller design compensating the ship motion (sinusoidal input) in the target tracking servo system

This paper proposes a controller that can exhibit the good performance in a servo system where step, ramp, and sinusoidal commands are mixed. In particular, the servo system applied to the naval gun system, the laser weapon system, the electro-optical tracking system installed on the ship must be able to follow the step and ramp commands necessary for target tracking and the sinusoidal command for stabilization of the ship motion. However, in the servo systems developed so far, type I and type II can control the steady-state error of step command and ramp command to zero, but a residual error occurred in sinusoidal command. This paper proposes a new controller with zero steady-state error of sinusoidal command. Using the Park’s Transformation concept used in the current of the AC motor, a PI controller was constructed by converting the sinusoidal drive command into a synchronous frame. The control law was derived from the relationship between the stationary frame controller and the synchronous frame controller. Furthermore, to detect the frequency required for conversion, frequency detection block was proposed. Steady-state conditions were found in the control zone (fine zone) separated by the error size and verified by simulation using an example plant.