Design and Development of a Self-Stabilizing, Autonomous Sailboat with Zero-Net Stored-Energy Use

Abstract

We are developing a robotic boat capable of sailing semi-autonomously for two years on the open ocean. Our design is a monohull sailboat with a weighted keel, no rudder, a controlled-angle sail, and an air-rudder to passively control the boats orientation relative to the wind without active control. We are working to optimize sail, keel and air-rudder parameters to maximize directional stability and forward speed. Given the boats polar plot (speed vs. angle to the wind) we have begun the development of navigation schemes that utilize the ocean currents to travel more quickly and avoid obstacles. The boat controls will be powered by solar panels mounted on the deck. Taking latitude, season and cloud cover into account, the boat will need to function with a daily-average power budget of about 0.4 W. Continuous use of the major electrical components in the sailboat requires much more than 0.4 W: the sail and air rudder servos consume 1.2 W in full capacity mode together, the Arduino Mega micro-processor consumes 0.84 W, and the GPS consumes 0.15 W. Thus, we can only use these components for brief time intervals, leaving them asleep or off for most of the time. One past iteration of the boat incorporated a freely rotating sail and tail to produce an angle of attack that generated lift for forwards propulsion, with an active water rudder for steering. We will test other self-stabilizing designs by interchanging parts to allow (1) Free or angle-controlled main sail; (2) tail angle controlled by servo or by a passive mechanism; (3) The presence or absense of an air rudder on the boat in addition to the tail; (4) The presense or total absense of a traditional water rudder.