Autopilot for a Personal Watercraft

Abstract: The objective in this thesis is to develop an autopilot for a personal watercraft (PWC) – popularly known as a jetski – that is capable of maneuvering in calm and rough waters alike. Maneuvering a PWC in calm waters is usually easy. It gets more challenging in rough waters, where environmental disturbances that can significantly destabilize the craft are present. In this project, two control strategies are developed; one with the sole focus of positioning and one with regard to environmental disturbances. The positioning controller can be thought of as an autopilot in calm conditions, i.e., no significant disturbances are present. It is divided into a PI-controller that handles thrust and a PID-controller that handles steering. These are tuned through a series of simulations on our PWC-model. To deal with the disturbances, simple models of these were constructed with the intention of crafting a control algorithm through simulations. However, after studying footage of PWC and other smaller craft in rough waters, it became clear that the sea-state is too unpredictable to rely on control algorithms devised from our simple and idealized wave-model. To obtain strategies that work in real life applications, strategies that are used by experienced (human) riders are brought up. Thus, depending on the direction of the waves, the PWC moves towards its desired position in a certain specific way. Whilst these strategies do not guarantee stability, they are deemed to give the PWC a viable chance of moving towards its desired position without capsizing in rough waters.