Technical field

The present disclosure relates to a hydrofoil system, and a marine vehicle provided with the hydrofoil system.

Background

Hydrofoils are underwater wings that provide lift that lifts the hull of a marine vehicle out of the water which reduces the total drag significantly. By raising the hull out of the water the influence of waves is reduced, which reduces noise and motions and provides less friction, less drag and a smoother ride. The fact that the marine vehicle moves with less resistance also facilitates use of electrical propulsion units, as less energy will be required.

The following patent documents have been identified as representative of the prior art.

US2017/0355429 shows a basic airplane design of a hydrofoil, with a front wing pair and a tail.

US3886884 shows a ship provided with a front, T-shaped hydrofoil and an aft hydrofoil. The front hydrofoil comprises a pair of simultaneously controllable, horizontal flaps, and the entire front hydrofoil is vertically turnable so as to act as a rudder. Aft hydrofoil comprises four independently controllable flaps, two starboard and two portside. The flaps and front hydrofoils are controlled and actuated so as to reduce rolling and pitching motion during rough seas, to control height above the water level, and to begin a banking motion in anticipation of yawing (turning) of the ship.

EP3168126 shows a standard T-shaped hydrofoil, additionally provided with controllable wing flaps. The inclination (wing tilt) of the hydrofoil wings is controlled by actuating said flaps. The hydrofoil has a water level sensor (30), gyroscopes, and triaxial accelerometers. When mounted on a vessel of catamaran type, the vessel is provided with four hydrofoils, two acting as keel, and two acting as rudders. The rudder hydrofoils are vertically rotatable when turning.

WO-2004/043773 relates to a high speed and stability watercraft comprise a lift arrangement with a fully submerged hydrofoil. DE102014005314 discloses a hydrofoil system comprising a hydrofoil housing and a propulsion unit.

Traditional means of achieving roll control are typically based on either passive solutions with surface piercing foils or complex and energy consuming rudder/flap configurations. Known solutions often have a complex solution to the balancing problem.

An object of the present invention is to achieve a hydrofoil system such that when mounted on a marine vehicle it provides a stable and less complex solution than previously known solutions. In addition, by making the hydrofoil system less complex it is also applicable at marine vehicles of different sizes.

Summary

The above-mentioned object is achieved by the present invention according to the independent claims.

Preferred embodiments are set forth in the dependent claims.

The purpose of the invention is to enable simple and energy efficient roll- stabilization of a marine vehicle provided with the hydrofoil system with a T-shaped hydrofoil mast- wing setup. The invention aims at solving the balancing problem in roll of the marine vehicle by placing a rudder, i.e. the vertical flap, on the mast, and thereby enables a transversal shift of the load point (much like balancing a broom with your hand). The force actuated by the vertical flap on the mast is relatively small but can efficiently move away the lift point and thereby initiate a turn or counteract a disturbance.

The hydrofoil system according to the present invention is very scalable, and may be applied on small pleasure marine vehicles (even kayaks) to city ferries providing a silent, stable, energy efficient and fast transport solution on the water that has a minimal disturbance on the surroundings in the form of noise and wake-wash.

Thus, the hydrofoil system disclosed herein achieves a rudder system, i.e. the vertical flap, which actively will stabilize the marine vehicle when in an active position, i.e. when the hull is above the water surface, and the propulsion units, e.g. the electrical motors, drive the marine vehicle. One important aspect is the way the rudder system is designed to balance the marine vehicle.

According to one embodiment the hydrofoil system comprises a mast and an airplane-like body having a front wing pair and a tail wing pair. The front wing pair is provided with two individually controlled propulsion units, e.g. thrust propellers, and may also be provided with two, simultaneously controlled, horizontal wing flaps. The mast is provided with a controllable, vertical flap. A controlling algorithm is provided for controlling the wing flaps, the propulsion units, and the vertical flap arranged at the mast, so as to achieve a smooth ride.

Below is included some explanations of the function of one embodiment of the present invention.

1) The main foil, being the front wing pair, provides the overall lift. It may be controlled by rotating the entire wing or by actuating the front wing flap pair.

2) The horizontal flap provides trim control to adjust the height above water.

3) The mast provides course stability and the vertical flap controls roll motion.

4) At least one propulsion unit on each main wing provides thrust and yaw control with thrust vectoring.

5) Sensors provide input to the vessels dynamic position. A control algorithm adjusts the control surfaces to maintain a stable ride.

6) One important feature is the simple way the vertical flap at the mast can control the lift point with a small effort.

Brief description of the drawings

Figure 1 is a perspective view schematically illustrating a hydrofoil system arranged on a marine vehicle, according to the present invention.

Figure 2 is a perspective view schematically illustrating a hydrofoil system arranged on a marine vehicle, according to an embodiment of the present invention.

Figure 3 is a block diagram illustrating the control unit and related units according to the present invention. Detailed description

The hydrofoil system will now be described in detail with references to the appended figures. Throughout the figures the same, or similar, items have the same reference signs. Moreover, the items and the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention.

With references to figures 1 and 2 the present invention relates to a hydrofoil system 2 comprising a mast 4. The hydrofoil system is structured to be attached to a hull of a marine vehicle 6 via the mast 4. The marine vehicle may be a small pleasure boat, but may also be a larger vessel, i.e. the hydrofoil system is scalable.

The mast has an upper end 8 structured to be attached to the hull, and a lower end 10 attached to a hydrofoil housing 12. The mast 4 has an essentially vertical extension when attached to the marine vehicle when it is in a resting state, such that the hydrofoil system 2 is below the water surface 14, i.e. the hull of the marine vehicle is in the water and no forces act on the marine vehicle. The hydrofoil housing 12 is elongated and has an extension along a longitudinal axis L. The housing 12 is attached to the lower end 10 of the mast 4 such that the longitudinal axis L has a direction along a longitudinal extension of the marine vehicle 6.

The hydrofoil system 2 comprises at least one controllable propulsion unit 16 arranged in connection to the hydrofoil housing 12. The at least one controllable propulsion unit may be directly or indirectly connected to the hydrofoil housing. If only one propulsion unit is provided it is preferably connected to the housing along the longitudinal axis L. In figure 1, one embodiment is shown where two propulsion units are provided which are indirectly connected to the housing via a front wing pair 32, and in figure 2 another embodiment is shown where four propulsion units are provided also connected to the housing via the front wing pair. In this embodiment the propulsion units at each wing have opposite major propulsion directions.

According to one embodiment the hydrofoil system also comprises a controllable, horizontal flap 18 rotatable about a first axis Al. Preferably, the first axis is perpendicular to the longitudinal axis L, and also to axis A2, and the first axis Al has advantageously an essentially horizontal direction when the marine vehicle is in the resting state. In a preferred variation the horizontal flap 18 is symmetrically arranged with regard to said longitudinal axis L. The object of the horizontal flap is to control the vertical level of the marine vehicle.

The mast 4 is provided with a controllable, vertical flap 20 being rotatable about a second axis A2. Preferably, the second axis is parallel to the mast 4. Thus, the vertical flap is attached to the mast via a hinge member enabling the flap to be set in a variable angle in relation to the longitudinal axis L in dependence of the control commands.

Also with references to the block diagram illustrated in figure 3, the hydrofoil system 2 further comprises a control unit 22 and a sensor system 24 comprising one or many sensors configured to measure at least one of inertial parameters, acceleration parameters, and rotational parameters of the marine vehicle, and to generate sensor signals 26 in dependence thereto, and to apply the sensor signals 26 to the control unit 22. In figure 3 the various parameters measured by the sensors are schematically indicated by arrows from right. The sensors comprise one or many of inertial measurement units, sensors configured to measure rotational parameters, and acceleration parameters in three dimensions. The sensors are configured to be mounted on the marine vehicle, e.g.

essentially along the axis of the mast.

The sensor system 24 also comprises a hull level sensor configured to measure a vertical distance D between a lower surface of the hull and the water surface, preferably when the lower surface of the marine vehicle is above the water surface, and to generate a level signal 28 in dependence thereto, and to apply the level signal 28 to the control unit 22.

In one embodiment the level sensor is an ultrasound sensor arranged at said hull. It may also be any type of mechanical sensor, e.g. a kind of rocker arm provided with a floater element at its distal end.

The control unit 22 is provided with a controlling algorithm to calculate and determine control commands in dependence of the sensor signals 26, and the level signal 28. The control unit is further configured to generate control signals 30 including the control commands, to control the vertical flap 20, preferably also the horizontal flap 18, and the at least one propulsion unit 16 such that the marine vehicle 6, when in an active state, is controlled to be above the water surface 14. When the marine vehicle is in an active state it moves forward and only the hydrofoil housing and a part of the mast is below the water surface.

According to one embodiment of the hydrofoil system the hydrofoil housing is an airplane-like body provided with a front wing pair 32 and a tail wing pair 34 comprising the horizontal flap 18. In one variation the front wing pair 32 is also provided with flaps, front wing flaps 36 (see figure 2), at each side of the housing, and which front wing flaps also are controllable by control commands generated by the control unit.

In a further embodiment the hydrofoil system comprises two identical propulsion units symmetrically connected to the hydrofoil housing, preferably by the front wing pair 32, and that the propulsion units are individually controlled by the control unit.

In another embodiment the at least one propulsion unit is an electrical motor, preferably an electrical motor provided with a propeller. The propulsion unit may also be any type of water jet turbine motor and contain gear boxes.

An energy source, e.g. a rechargeable battery, is provided, e.g. installed on the marine vehicle and capable of suppling energy to the various parts of the system. The parts of the system arranged in or in connection to the hydrofoil housing are provided with electrical energy via electrical cables running within the mast. Thus, the parts of the system comprise the at least one propulsion unit, and electrical servos providing rotational movements to the horizontal and vertical flaps.

According to a further embodiment the controlling algorithm includes functions for calculating and determining control commands.

Initially the sensor signals need to be filtered and combined to provide a stabilized measured signal regarding the attitude and level of the marine vehicle, this is performed e.g. by using a Kalman filter. The stabilized signal is then provided to the controlling algorithm where a difference value is determined, being the difference between a wanted value, i.e. a value reflecting the direction the user would like the marine vehicle to have, and the present actual value, i.e. the measured signal. The difference value is the“error” that the control algorithm will try to minimize. This is performed by also requiring that specified sub-conditions are taken into account, regarding e.g. maximal engine power of the motors, maximal steering angles of the flaps, or the energy consumption, e.g. minimizing the energy consumption.

The present invention also relates to a marine vehicle provided with the hydrofoil system which has been described above.

The present invention is not limited to the above-described preferred embodiments.

Various alternatives, modifications and equivalents may be used. Therefore, the above embodiments should not be taken as limiting the scope of the invention, which is defined by the appending claims.