Method for Controlling an Unmanned Surface Vessel

Abstract

This patent describes a method for steering an unmanned surface vessel consisting of a hull, keel, and non-self-tacking rigid wing sail. Unlike conventional vessels, it doesn't require a rudder. Steering is achieved by rotating the wing sail around a vertical axis using an actuator. The center of lateral resistance is spaced aft of the center of windage, balancing the vessel to the wind. The vessel maintains various angles relative to the wind and holds a port or starboard tack without active steering. The sail position only needs changing when a new course is desired. The vessel can progress at all angles to the wind, whether by a zigzagging course or a straight line. This method eliminates the need for an active rudder to maintain course, reducing power consumption and component wear.

Description

FIELD

The present disclosure generally relates to autonomous vehicles and relates more specifically to sail-propelled unmanned surface vehicles (vessels).

BACKGROUND

There is a growing industry in developing unmanned surface vessels to conduct inshore and offshore tasks that previously were completed using manned vessels. Some of the missions these robotic boats are tasked with include collection of oceanic data using sensors, observation, surveillance, and bathymetric surveying. Since many of these vessels are stationed at sea for long periods, various energy harvesting systems have been developed, allowing the boats to operate indefinitely without fuel limitations. Some of the energy sources used by current autonomous boats include wind, solar, wave energy, and the thermal gradient in the top layer of the ocean.

Two significant challenges in this industry are creating efficient and reliable boats. Since many of the long-endurance vessels are energy harvesting (mainly wind and solar power), overall power availability is low, and the vessel needs to function within these parameters. Additionally, because no humans are available to fix problems, the vessels need to be extremely durable to be able to function reliably for months in the unforgiving ocean environment.

Rudders and supporting hardware are a primary source of failure. To steer a boat in large waves, the rudder and actuator are constantly in motion, consuming power and causing heavy wear. Furthermore, the smaller the boat is, the more aggressive rudder action needs to be to maintain a course in tumultuous seas. In addition, an active controller or processor and navigation sensors are required to provide inputs to the rudder actuator, requiring additional power. Beyond structural failure, rudders are prone to other malfunctions such as getting jammed by debris or biofouling.

For boats propelled by propellers, one solution for eliminating the use of a rudder is to use two propellers side by side with steerage achieved using variable thrust.

Various means of steering sailboats without a rudder have been devised. Sailing schools often teach students rudderless sailing. This involves adjusting the center of effort and the center of lateral resistance to achieve a balance, so the boat sails in the desired direction. Center of lateral resistance is changed by moving the daggerboard up and down or COG fore or aft. Center of effort is moved by adjusting the angle or size of the sails. While this is an effective means of sailing without a rudder, it does require continuous active inputs provided by the crew for the boat to stay balanced on desired direction of heading.

Another method of steering a boat without a rudder is demonstrated with children's free-sailing boats. These are toy boats used on ponds, that will sail indefinitely at a certain angle to the wind. The center of effort is spaced appropriately ahead of the center of center of lateral resistance to allow the boat to maintain course relative to the wind without a rudder. While these boats do not require active inputs to maintain a course, they will not maintain a starboard or port tack because the sails are self tacking. If the boat is pushed by a wave or other external force onto the opposite tack, the sails will simply switch sides and the boat will start sailing at the opposite angle. Additionally, these boats do not make use of actuators to adjust the angle of the sails, therefore angle of travel cannot be changed.

Other methods of self steering for have been developed for conventional sailboats. Crewed boats have long used wind guided and/or electronic steering systems. Most of these systems have many complex moving parts and are vulnerable to failure over the long term. Electronic steering systems also require power for processors and actuators. Most of these systems also require a rudder.

Another method of steering a sailboat without requiring active steering inputs is described in t U.S. Pat. No. 9,616,984. This patent presents a vessel operating method utilizing a self-tacking wing sail, a rudder, and a keel. While this invention maintains various balanced headings relative to the wind, it still relies on a rudder. The rudder is fixed at different positions to achieve different headings to the wind. Additionally, a self-tacking sail is required for proper operation.

Another method of steering a sailing vessel without a rudder is described with patent US20140283725A1. This invention describes a sailing vessel which is rudderless, comprising of a keel, a hull and a wing sail. The inventor emphasizes the desire to eliminate a rudder due to its limited life expectancy. Steering is achieved by changing the center of effort and center of lateral resistance by adjusting the center of gravity. This adjustment is made possible by moving an internal mass with an actuator. Shifting internal mass impacts both the center of lateral resistance and center of effort, enabling the vessel to sail at different angles to the wind without a rudder.

SUMMARY

The appended claims may serve as a summary of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1: Perspective View of the Sailboat Configuration

FIG. 1 illustrates a perspective view of the sailboat configuration according to the present invention. It shows the sailing vessel comprising a rigid wing sail, a hull, and a keel. The wing sail is positioned on a mast and can be adjusted to various angles relative to the hull.

FIG. 2: Side View of the Wing Sail Configuration

FIG. 2 provides a side view of the wing sail configuration. It depicts the sail angled longitudinally to the hull. Position of the keel relative to the sail can clearly be seen with center of lateral resistance and center of effort marked.

FIG. 3: Top View of the Sailboat Control System

FIG. 3 presents a top view of the sailboat control system. It showcases the positioning of the center of lateral resistance and the center of effort. The specific distance between these points achieves balance, allowing the vessel to sail indefinitely at multiple angles to the wind without active inputs. Arrows indicate the two forces on the vessel to turn downwind and upwind.

FIG. 4: Sailing Angles

FIG. 4 Illustrates the vessel sailing at different angles to the wind with the sails angled at different positions relative to the hull.

DETAILED DESCRIPTION

The present invention discloses a novel method of controlling an unmanned surface vessel 10 without relying on a traditional rudder. The invention pertains to a sailing vessel comprising a rigid wing sail 4, a hull 1, and a keel 2. By adjusting the angle of the wing sail 4 relative to the hull, the vessel's direction of travel 11 relative to the wind 9 can be determined. Unlike self-tacking sails, the wing sail 4 in this invention maintains the vessel's course on either the port or starboard tack. Should external forces, such as waves or collisions, cause the vessel to switch tack, it will naturally turn downwind and subsequently round back to its original tack. This sailboat control system achieves balance and allows for indefinite sailing at multiple angles to the wind 13, without the need for active inputs like adjusting the sail angle or making continuous rudder corrections, as commonly seen in conventional sailboats. This balance is achieved by positioning the center of lateral resistance 5 at a specific distance aft of the center of effort 6. The boat exhibits a tendency to point downwind 8 due to this configuration, but it is counteracted by the air rudder effect 7 generated by the wing sail, which aims to turn the vessel upwind. The rudder effect 7 of the wing sail 4 becomes more pronounced as the boat points further downwind, resulting in a balance where these two forces 7,8 are equal. At this equilibrium point, the sail 4 is angled for optimal sailing performance, and the lift generated as the air passes over the forward face of the sail provides forward thrust for the vessel.

As depicted in FIG. 4, this balance is maintained across a wide range of angles 13, allowing the wing sail 4 to be positioned at multiple angles relative to the hull, ensuring stable sailing at various angles relative to the wind 9. Notably, for straight downwind sailing 14, the sail is angled longitudinally to the hull, contrary to the conventional practice of angling sails near perpendicular to the hull. In this invention, such a perpendicular configuration is unbalanced and would require the use of a rudder or other active inputs to maintain the desired course. By angling the wing sail longitudinally to the hull, with the leading edge pointing upwind, the stern of the vessel will weathercock into the wind, causing the bow to point downwind. The resulting turbulence and friction generated as the wind flows over the vessel and sail, despite being less than with a perpendicular sail orientation, will facilitate a downwind course.

The present invention capitalizes on the reliable and sustained wind direction that can persist for hours or even days. By leveraging this characteristic, the invention enables the sailboat to maintain its course with minimal or no active inputs, thereby reducing power consumption and minimizing wear on the actuators.

Claims

1. A method for steering an unmanned surface vessel, comprising: a) a rudderless hull;b) a keel; andc) non-self-tacking wing sail controlled by an actuator, wherein the center of effort is placed ahead of the center of lateral resistance so the vessel remains balanced at different angles to the wind and remains on port or starboard tack depending on the wing-sail angle relative to the hull, and the direction of travel is changed by adjusting the angle of the sail.

2. The unmanned surface vessel control system of claim 1, further comprising a processor connected to an electronic navigation system, wherein the processor periodically checks the boat's position and adjusts the sail position based on programmed settings or AI-derived decisions.

3. The unmanned surface vessel control system of claim 1, further comprising a remote communication and telemetry system, enabling a human operator to monitor the vessel's status and send commands to change the sail position as required.

4. An unmanned surface vessel of claims 1, 2, or 3, further comprising two or more sails.

5. A control system for a boat fitted with an auxiliary propeller propulsion system, comprising: a) a rudderless hull;b) a keel; andc) non-self-tacking wing sail controlled by an actuator, wherein the center of effort is placed ahead of the center of lateral resistance so the vessel remains balanced at different angles to the wind and remains on port or starboard tack depending on the wing-sail angle relative to the hull, and the direction of travel is changed by adjusting the angle of the sail.d) a rudder selectively operable in propeller propulsion mode, wherein the rudder is locked in neutral position during the sailing mode.

6. The sailboat control system of claim 6, wherein the auxiliary propeller propulsion system is operable when wind conditions are insufficient for sailing or for tight maneuvering.

7. The sailboat control system of claim 6, further comprising a control mechanism that switches between the sailing mode and the propulsion mode based on remote user inputs or predetermined settings executed by an onboard processor.

8. The sailboat control system of claim 6, wherein the actuator adjusts the angle of the wing sail automatically based on wind conditions, and the rudder remains locked in the neutral position during the sailing mode.

9. The sailboat control system of claim 6, wherein the rudder is operable independently from the wing sail when the boat is in the propulsion mode.