Abstract
This paper analyzes stability of pleasure boats controlled by human in order to develop an electronic control steering system of those boats. At first, the equation of motion of pleasure boats in the global coordinate is derived. This equation of motion is used to compute a man-machine system model for controlled pleasure boats. Stability of pleasure boats controlled by proportional action of human is analyzed based on the man-machine system model. It can be seen that stability region can be enlarged when a forward gazing point is long. To keep such long gazing point, electronic control steering system should give adequate reaction force through the helm into captains so that they can grasp their input for the helm without any instruments.
