WO2014083046A1

WO2014083046A1 - Propulsion system for a vehicle

Info

Publication number: WO2014083046A1
Application number: PCT/EP2013/074839
Authority: WO
Inventors: Nicholas Charles TOWNSEND; Ramanand Ajit SHENOI
Original assignee: University of Southampton
Current assignee: University of Southampton
Priority date: 2012-11-30
Filing date: 2013-11-27
Publication date: 2014-06-05
Anticipated expiration: 2015-05-30
Also published as: GB2508399B; GB2508399A

Abstract

A vehicle (6) comprising: a flywheel (14) having a spin axis (16), a drive system (18) adapted to rotate the flywheel about the spin axis, a gimbal support (12) in which the flywheel is rotatably mounted for rotation about the spin axis, the gimbal support being rotatably mounted to a fixed base (4) in the vehicle for precession rotation about a precession axis (V) which is orthogonal to the spin axis of the respective flywheel, wherein the flywheel, drive system, and gimbal support are comprised in a gyroscopic system (2) mounted and adapted to cause precession rotation about the precession axis when the vehicle moves by at least one of roll motion, pitch motion and yaw motion, a power take-off device (22) coupled to the gimbal support, the power take-off device comprising a mechanism which damps the precession rotation to generate power in the power take-off device, and a propulsion system (24) for providing motive power to the vehicle, the propulsion system being coupled, directly or indirectly, to the power system to propulse the vehicle.

Description

PROPULSION SYSTEM FOR A VEHICLE

The present invention relates to a vehicle having a propulsion system. The present invention also relates to a method of propulsing a vehicle.

Some vehicles, such as Autonomous Underwater Vehicles (AUVs), depend on stored energy for their operation. Most systems rely on batteries. However, many high performance batteries are prohibitively expensive for some vehicle applications, in particular AUV applications. Large battery packs represent a significant proportion, typically around 20%, of the total vehicle mass.

To increase AUV autonomy and extend mission deployments, in-situ battery charging and/or alternative power systems are required. In the past, internal combustion engines have been used to power AUVs. However, these systems are limited as additional power is needed to expel the exhaust gases at depths greater than 200m. The Royal Swedish Navy has used Stirling engines and (Slocum) gliders have been developed using ocean temperature gradients and battery power to generate propulsion. Fuel cells have been trial led on AUVs and solar powered AUVs have also been developed. Although solar powered AUVs potentially offer unlimited mission durations, they are limited to night-time missions and daylight recharging strategies, and the solar energy collectors are susceptible to bio-fouling.

There is therefore a need in the art for a vehicle, such as an autonomous underwater vehicle, having a propulsion system which provides motive power to the vehicle and can be more efficiently powered.

The present invention aims at least partly to meet this need and to provide a vehicle which can employ efficiently harvested energy to power a propulsion system.

Accordingly, the present invention provides a vehicle comprising:

a flywheel having a spin axis,

a drive system adapted to rotate the flywheel about the spin axis,

a gimbal support in which the flywheel is rotatably mounted for rotation about the spin axis, the gimbal support being rotatably mounted to a fixed base in the vehicle for precession rotation about a precession axis which is orthogonal to the spin axis of the flywheel,

wherein the flywheel, drive system, and gimbal support are comprised in a gyroscopic system mounted and adapted to cause precession rotation about the precession axis when the vehicle moves by at least one of roll motion, pitch motion and yaw motion,

a power take-off device coupled to the gimbal support, the power take-off device comprising a mechanism which damps the precession rotation to generate power in the power take-off device, and

a propulsion system for providing motive power to the vehicle, the propulsion system being coupled, directly or indirectly, to the power take-off device to receive therefrom power generated by the power take-off device which is converted to motive power to propulse the vehicle.

Typically, the precession axis is substantially vertical and the spin axis is substantially horizontal.

Preferably, the spin axis substantially coincides with at least one of the roll motion, pitch motion and yaw motion axes of the vehicle, more preferably at least one of the roll motion and pitch motion axes of the vehicle. Preferably, an intersection of the precession and spin axes substantially coincides with an intersection of at least two of the roll motion, pitch motion and yaw motion axes of the vehicle, more preferably all of the roll motion, pitch motion and yaw motion axes of the vehicle.

Typically, the drive system is adapted to rotate the flywheel about the spin axis at a spin rate of from 1000 to 50000 revolutions per minute, optionally from 5000 to 20000 revolutions per minute, further optionally about 0000 revolutions per minute.

The drive system may be adapted to rotate the flywheel about the spin axis at a constant spin rate or at a variable spin rate.

The mechanism may be adapted linearly or non-linearly to damp any oscillatory and rotational motion of the gimbal support about the precession axis. The mechanism may be a hydraulic mechanism. In a preferred embodiment, the apparatus further comprises a storage device for storing power generated by the power take-off device, and the propulsion system is coupled, directly or indirectly, to the storage device to receive stored power therefrom.

In one embodiment, the apparatus may further comprise an electrical generator system comprised in or coupled to the power take-off device. The electrical generator system may be coupled to the storage device which is adapted for storing electrical power, and the propulsion system may be adapted to be driven by electrical power.

In another embodiment, the storage device is adapted for storing kinetic energy, such as a second flywheel.

In preferred embodiments, the vehicle is an autonomous underwater vehicle and the gyroscopic system is adapted to cause precession rotation about the precession axis when the vehicle moves by at least one of roll motion, pitch motion and yaw motion as a result of wave or other excitation on an exterior of the autonomous underwater vehicle. Typically, the vehicle is a manned or unmanned submarine comprising a substantially cylindrical elongate hull.

In one embodiment, the apparatus may further comprise a first control system adapted to control at least one of the damping of the precession rotation of the gimbal support and the rotation speed of the flywheel about the spin axis to maximise the power generated in the power take-off device. The apparatus may optionally further comprise a second control system adapted to control at least one of the dampmg of the precession rotation of the gimbal support and the rotation speed of the flywheel about the spin axis to control at least one of the roll motion, pitch motion and yaw motion of the vehicle.

The present invention further provides a method of propulsing a vehicle, the vehicle having mounting therein a gyroscopic system comprising a flywheel having a spin axis, a drive system adapted to rotate the flywheel about the spin axis, and a gimbal support in which the flywheel is rotatably mounted for rotation about the spin axis, the gimbal support being rotatably mounted to a fixed base in the vehicle for precession rotation about a precession axis which is orthogonal to the spin axis of the flywheel, the method comprising the steps of:

(a) rotating the flywheel so that when the vehicle moves by at least one of roll motion, pitch motion and yaw motion, that motion causes precession rotation of the gimbal support about the precession axis,

(b) when the vehicle moves by at least one of roll motion, pitch motion and yaw motion, damping the precession rotation to generate power in a power take-off device coupled to the gimbal support, and

(c) using the power to provide motive power to the vehicle propulsed by a propulsion system.

In a preferred embodiment, the vehicle is an autonomous underwater vehicle, in step (b) when the autonomous underwater vehicle moves by at least one of roll motion, pitch motion and yaw motion as a result of wave or other excitation on an exterior of the autonomous underwater vehicle, that motion causes precession rotation about the precession axis, and the precession rotation is damped to generate power in a power take-off device coupled to the gimbal support.

Preferably, steps (a) and (b) are carried out when the autonomous underwater vehicle is at the surface of a body of water and step (c) is carried out at least partly when the autonomous underwater vehicle is submerged beneath the surface of the body of water or at least partly when the autonomous underwater vehicle is at the surface of a body of water. Typically, steps (a) and (b) are carried out when the autonomous underwater vehicle is in turbulent water and step (c) is carried out at least partly when the autonomous underwater vehicle is submerged beneath the surface of the body of water or at least partly when the autonomous underwater vehicle is at the surface of a body of water.

Preferably, the precession axis is substantially vertical and the spin axis is substantially horizontal. Preferably, the spin axis substantially coincides with at least one of the roll motion, pitch motion and yaw motion axes of the vehicle, more preferably at least one of the roll motion and pitch motion axes of the vehicle. Preferably, an intersection of the precession and spin axes substantially coincides with an intersection of at least two of the roll motion, pitch motion and yaw motion axes of the vehicle, more preferably all of the roll motion, pitch motion and yaw motion axes of the vehicle.

Typically, in the method of the invention the flywheel is rotated about the spin axis at a spin rate of from 1000 to 50000 revolutions per minute, optionally from 5000 to 20000 revolutions per minute, further optionally about 10000 revolutions per minute.

In a preferred embodiment, the method further comprises actively damping the oscillatory and rotational motion of the gimbal support about the precession axis to provide a gyrostabilising effect.

Typically, the damping comprises hydraulic damping.

The method may further comprise the step, between steps (b) and (c) of: (d) storing power generated by the power take-off device; and step (c) uses the stored power.

In a preferred embodiment, the precession rotation generates electrical power in an electrical generator system comprised in or coupled to the power take-off device. The propulsion system may be driven by electrical power. The electrical power may be stored.

In another embodiment, the precession rotation generates power in the form of kinetic energy which is stored in step (d). Typically, the kinetic energy is stored in a second flywheel. Optionally, the kinetic energy is selectively stored in or outputted from the second flywheel dependent upon input variables associated with a demand for propulsion and/or gyroscopic stability control of the vehicle.

In a preferred embodiment, the autonomous underwater vehicle is a manned or unmanned submarine comprising a substantially cylindrical elongate hull. In this specification, the term "flywheel" is intended to refer to any rotatable body suitable for incorporation into a gyroscope, as well as such a body formed as a flywheel.

The preferred embodiments of the present invention can provide a gyroscopic system which is coupled to a power take-off device. The gyroscopic system can harvest wave energy and convert that energy to provide motive power to the propulsion system of the vehicle. The harvested energy may be stored for subsequent use to provide motive power, or optionally to provide power to other elements of the vehicle.

Although the preferred embodiments of the present invention provide a gyroscopic system in a marine vessel which harvests wave energy, and optionally energy from other external sources, such as from water or wind movement, the present invention may be used in any vehicle having a propulsion system requiring input motive power where movement of the vehicle itself, particularly under the influence of external forces, can cause precession of a gyroscope, and which precession can be damped to harvest energy.

The gyroscopic system can be adapted selectively additionally to function as a passive or active gyrostabiliser which is capable of generating stabilising moments for stabilizing a marine vessel. The gyrostabiliser of the preferred embodiments of the present invention can improve the operation of the vessel by, for example: reducing any undesirable motions of the vessel; reducing the incidences of sea sickness and improving habitability; reducing the physical and mental fatigue (and human errors) of crew and/or passengers; and reducing drag, improving speed and/or fuel consumption.

The gyrostabiliser systems of the preferred embodiments of the present invention have particular application as a motion control device for marine craft, though other motion control or vehicular stabilising applications will be apparent to those skilled in the art. The moment generator may be used or adapted to provide a desired motion control by preventing or reducing undesired motions of a moving vehicle or object or by causing desired motions of an otherwise stationary, in at least the direction of imparted motion, of a stationary vehicle or object.

Embodiments of the present invention will now be described by way of example only, with reference to the accompanying drawings, in which:-

Figure 1 schematically illustrates the moments acting around each orthogonal axis of a gyroscope;

Figure 2 schematically illustrates a gyroscopic in a vehicle in accordance with an embodiment of the present invention; and

Figure 3 is a schematic diagram of an autonomous underwater vehicle incorporating the gyroscopic stabiliser system of Figure 2 in accordance with another embodiment of the present invention.

Motion control systems have been fitted to a variety of marine structures and vessels. One known comprises a gyrostabiliser. Gyrostabiliser systems generate stabilising moments entirely within the hull of a vessel without simply relying on providing sufficient movable weight. Such gyrostabiliser systems are becoming of increased interest in the marine vessel art, and are a re-emerging solution.

A gyrostabiliser uses the inertial property of a rotating body or flywheel to apply moments to a vehicle (or other object) to alter the amplitude of oscillatory motions that a vehicle suffers when subject to external excitation (e.g. the wave excitation of a ship).

Referring to Figure 1, the moments acting around each orthogonal axis of a gyroscope, assuming the xyz axes are chosen to coincide with the principal axes of inertia of the body, rotating with the body but not spinning with the body, and a symmetrical rotating body or flywheel in x and y axes, (i.e. I=I_xx=Iyy and Ixy⁼Iyx⁼Ixz⁼Izx⁼Iyz⁼Izy=0), can be expressed as;

M_y = l{(b_y + ω_χω_ζ )- Ι_Βω_χ (ω_ζ + ψ)

Μ_: = Ι_Β (ώ_ζ + ψ)

where:

Μ_χ, My and M_z are, respectively, the moment acting about the x, y or z axis,

I is the mass moment of inertia of the rotating body or flywheel, about the x or y axis, Izz is the mass moment of inertia about the z axis,

ω_χ co_y and ω_ζ are, respectively, the rate of rotation of the gyroscope about the x, y or z axis,

ώ_χ ώ_γ and ώ_ζ are, respectively, the angular acceleration of the gyroscope about the x, y or z axis,

Ψ is the spin rate of the rotating body or flywheel, and

^■φ is the angular acceleration of the rotating body or flywheel.

When operating, the rotating body or flywheel within the gyroscope rotates about an axis, which itself is free to rotate. Therefore, in addition to the usual terms that account for moments when the rotating body or flywheel is not spinning, Equations. (2) and (3) indicate the existence of additional gyroscopic moments, that act around the x and y axes (i.e. M_x = Ι_ζω_νψ and M_y ~ -1_:ω_χψ ). These gyroscopic moments are used to apply stabilising moments in gyrostabilisers.

In a gyrostabiliser, one of the gyroscopic axes is fixed to the axis of the vessel about which the undesirable (target) motion occurs. The other axis of the gyroscope is permitted to rotate independently of the vessel.

In one particular arrangement, known as a passive gyrostabiliser system, the moment causing the undesirable motion is reacted by the gyroscope and results in a rotation of the gyroscope about its free axis, which rotation may be damped by the provision of damping elements.

In another particular arrangement, known as active gyrostabiliser system, the gyroscope is forced to rotate about its free axis, such rotation herein being known as nutation, resulting in a motion-controlling moment being generated about the ship- fixed axis of the gyroscope.

For both passive and active gyrostabilisers the stabilising effect is dependent on;

• The mass-moment-of-inertia of the rotating body or flywheel about the spin axis, l_: , which is dependent on both the magnitude and distribution of the weight within the body or flywheel,

• The spin rate of the body or flywheel about the spin axis {ψ ) and,

• The rate of rotation of the gyroscope about its free axis, ( ω_χ oim_y , depending on axis definition).

The rate of rotation of the rotating body or flywheel of the gyroscope about its free axis (ω_χ or <a_y ), in a gyrostabiliser, must retain a phase relationship to the excitation.

In an active gyrostabiliser, where this rotation ( ω_χ οτω_γ ) is forced by nutation, a greater magnitude of rotation can be generated (for a given excitation), compared to an equivalent passive system, providing a greater stabilising effect. However in currently commercialised active gyrostabiliser systems, the gyroscopic moments act solely about the desired ship-fixed axis of rotation when the plane of the flywheel is oriented in one axis (dependent on the arrangement and orientation of the system). Thus, the gyroscopic moments act around the desired ship-axis of rotation in proportion to the cosine of its angular displacement from this axis but also (undesirably) about another axis of the ship in proportion to the corresponding sine function. To limit the action of the undesirable moments, currently used gyrostabiliser systems only perform small perturbations (for example, a maximum perturbation of 60 degrees is known for one such system) of the gyroscope about the desired mean position, with the effect of limiting the stabilising moments that can be achieved.

Referring to Figure 2, there is shown schematically a gyroscopic system for incorporation into a vehicle in accordance with a first embodiment of the present invention. The gyroscopic system, designated generally as 2, comprises a fixed base 4 which is in use affixed to a vehicle 6, such as a hull of a marine vessel 6. The base 4 comprises two vertically spaced base elements 8, 10 mounted to the vehicle 6 between which is rotatably mounted a gimbal support 12 which can rotate about a vertical axis V.

The gimbal support 12 supports a flywheel 14 therein, with a shaft 16 of the flywheel 14 being rotationally mounted in the gimbal support 12. A spin motor 18 is mounted to the shaft 16 of the flywheel 14. The spin motor 18 is adapted to spin the respective flywheel 14 in a respective angular rotational direction about a spin axis S which is orthogonal to the vertical axis V about which the gimbal support 12 rotates. The flywheel 14 may be arranged, together with the spin motor 18, to spin in a selected one of two opposite rotational directions. The spin motor 18 comprises a drive system for rotating the flywheel 14 at a selected spin rate and/or acceleration. Typically, the drive system is adapted to rotate the flywheel 14 about the spin axis at a spin rate of from 1000 to 50000 revolutions per minute, optionally from 5000 to 20000 revolutions per minute, further optionally about 10000 revolutions per minute. The drive system may be adapted selectively to rotate the flywheel 14 about the spin axis at a constant spin rate or at a variable spin rate.

The gimbal support 12 is fixedly mounted on respective shafts 20, 20' respectively fitted to the base elements 8, 10 so that the gimbal support 12 and the respective shafts 20, 20' can rotate about the vertical axis V. Such rotation of the gimbal support 12 about the vertical axis V permits precession rotation of the gimbal support 12 about a precession axis V which is orthogonal to the spin axis S of the flywheel 14.

Thus, in the illustrated embodiment the precession axis is substantially vertical and the spin axis is substantially horizontal.

In an alternative configuration of the gyroscopic system in the invention, the base comprises two horizontally spaced base elements and the gimbal support could be mounted to precess about a vertical axis. Typically, the spin axis substantially coincides with at least one of the roll motion, pitch motion and yaw motion axes of the vehicle, more typically at least one of the roll motion and pitch motion axes of the vehicle. Typically, an intersection of the precession and spin axes substantially coincides with an intersection of at least two of the roll motion, pitch motion and yaw motion axes of the vehicle, more typically an intersection of all of the roll motion, pitch motion and yaw motion axes of the vehicle.

Accordingly, the flywheel 14, spin motor 18 comprising a drive system, and gimbal support 12 are comprised in a gyroscopic system mounted and adapted to cause precession rotation about the precession axis when the vehicle moves by at least one of roll motion, pitch motion and yaw motion.

In alternative embodiments, the gyroscopic system may comprise plural flywheel/gimbal support assemblies, either coupled together to a single energy harvesting and power utilising system or independently operating to provide independent energy harvesting and utilisation.

A power take-off device 22 is coupled to the gimbal support 12. The power take-off device 22 comprises a switchable mechanism 22 which is selectively couplable to the gimbal support 12, directly or indirectly by one or both of the shafts 20, 20', controllably to damp any rotational precession rotation of the gimbal support 12. The mechanism is adapted linearly or non-linearly, optionally in a selective manner, to damp any oscillatory and rotational motion of the gimbal support 12 about the precession axis. Such damping of the precession rotation generates power in the power take-off device 22. The power take-off device 22 may be a hydraulic mechanism. Typically, the damping comprises hydraulic damping, although electromechanical or other damping may be employed.

The vehicle comprises a propulsion system 24 for providing motive power to the vehicle. The propulsion system 24 is coupled, directly or indirectly, to the power take-off device 22 to receive therefrom power generated by the power take-off device 22 which is converted to motive power to propulse the vehicle. In the illustrated embodiment, a storage device 26 for storing power generated by the power take-off device 22 is connected to the power take-off device 22 and the propulsion system 24 is coupled, directly or indirectly, to the storage device 26 to receive stored power therefrom. In one embodiment, the storage device 26 is adapted for storing kinetic energy, for example in a subsidiary storage flywheel. The flywheel 14 may also be employed to store kinetic energy.

In one embodiment, an electrical generator system 28 is comprised in or coupled to the power take-off device 22. The electrical generator system 28 may be coupled to the storage device 26 which is correspondingly adapted for storing electrical power, and the propulsion system 24 is adapted to be driven by electrical power.

In one embodiment, a nutation motor 30 is mounted on shaft 20 and is adapted to rotate the gimbal support 12 and the supported rotating flywheel 14 about the vertical axis V. The nutation motor 30 in this embodiment comprises a second drive system for rotating the gimbal support 12 and the supported rotating flywheel 14 about a nutation axis V when the gyroscopic system 2 is adapted to act as an active gyrostabiliser system. In such an active gyrostabiliser system the orientation of the gimbal support 12 for the flywheel 14 defines the direction of the applied moment on the fixed base 4 and therefore the vehicle 6 and the angular velocity of precession or nutation of the flywheel 6 defines the magnitude of the applied moment.

The power take-off mechanism 22 may optionally be wholly or partly incorporated into the nutation motor or a controller therefor, for example by electromagnetic damping, and may be adapted to provide energy retrieval by regenerative braking or damping.

Referring to Figure 3, in preferred embodiment of the present invention the vessel 40 is an autonomous underwater vehicle, for example a manned or unmanned submarine comprising a substantially cylindrical elongate hull. The gyroscopic system 2 is adapted to cause precession rotation about the precession axis V when the vessel 40 moves by at least one of roll motion (indicated by arrow R) about axis X, pitch motion (indicated by arrow P) about axis Y and yaw motion (indicated by arrow T) about axis Z as a result of wave or other excitation (indicated by arrows W) on an exterior 42 of the autonomous underwater vehicle.

As shown in Figure 2, in the illustrated embodiment the gyroscopic system 2 further comprises a first control system 32 adapted to control at least one of the damping of the precession rotation of the gimbal support 12 and the rotation speed of the flywheel 14 about the spin axis to maximise the power generated in the power takeoff device 22. In other words, the first control system 32 controls the gyroscopic system 2 selectively to provide an optimal power output for providing motive power to the vessel 40 and/or to supply power to on-board equipment, such as sensors and other systems and subsystems. Furthermore, the gyroscopic system 2 further comprises a second control system 34 adapted to control at least one of the damping of the precession rotation of the gimbal support 12 and the rotation speed of the flywheel 14 about the spin axis to control at least one of the roll motion, pitch motion and yaw motion of the vehicle. In other words, the second control system 34 controls the gyroscopic system 2 selectively to provide a desired gyroscopic control to the vessel 40.

In use, the gyroscopic system is used in a method of propulsing a vehicle.

In the method the gyroscopic system as described above is mounted in the vehicle 40. The flywheel 14 is rotated at the desired angular velocity. When the vehicle moves by at least one of roll motion, pitch motion and yaw motion, the gimbal support 12 is caused to precess about the precession axis, and the precession rotation is damped to generate power in the power take-off device 22 coupled to the gimbal support 22. The power is used to provide motive power to the vehicle 40 propulsed by the propulsion system 24.

In the illustrated embodiment in which the vehicle 40 is an autonomous underwater vehicle, typically a manned or unmanned submarine comprising a substantially cylindrical elongate hull 42, when the autonomous underwater vehicle moves by at least one of roll motion, pitch motion and yaw motion as a result of wave or other excitation on an exterior of the autonomous underwater vehicle, that motion causes precession rotation about the precession axis, and the precession rotation is damped to generate power in the power take-off device 22 coupled to the gimbal support 12.

The power generated by the power take-off device 22 may be stored and the provision of motive power may use the stored power.

In one embodiment, the precession rotation generates electrical power in the electrical generator system 28, the electrical power is stored in the storage device 26 which may comprise a battery pack and the propulsion system 24 is driven by electrical power.

In another embodiment, the precession rotation generates power in the form of kinetic energy which is stored, for example in a second flywheel, and the kinetic energy is selectively stored in or outputted from the second flywheel dependent upon input variables associated with a demand for propulsion and/or gyroscopic stability control of the vehicle 40.

The power generation typically is carried out when the autonomous underwater vehicle is at the surface of a body of water. The provision of motive power is carried out at least partly when the autonomous underwater vehicle is submerged beneath the surface of the body of water or at least partly when the autonomous underwater vehicle is at the surface of the body of water. The power generation is typically carried out when the autonomous underwater vehicle is in turbulent water and provision of motive power is carried out at least partly when the autonomous underwater vehicle is submerged beneath the surface of the body of water or at least partly when the autonomous underwater vehicle is at the surface of the body of water.

In a typical cycle, the autonomous underwater vehicle is located at the surface of the body of water in a recharge mode in which the wave energy is harvested and stored and then in a propulsion mode the autonomous underwater vehicle is submerged and propulsed at last partly using the stored harvested energy. When the stored energy is depleted, the autonomous underwater vehicle is raised to effect a subsequent recharge mode. In some embodiments, the oscillatory and rotational motion of the gimbal support about the precession axis may be actively damped to provide a gyroscopic stabilising effect in the vehicle. The preferred embodiments of the present invention can provide a gyrostabiliser system which can be passively or actively damped, by manual selection or automatic control, and also a further active continuous nutation mode is possible in which the gyrostabiliser flywheel is rotationally nutated in a continuous manner to produce opposing moments to the roll motion excitation moments.

The gyrostabiliser system may be employed not only in autonomous underwater vehicles but also in other vessels such as small to medium sized vessels that require stabilisation specifically at low/no speed, for example research vessels, rescue, military and leisure craft and energy efficient operation that benefits from wave energy harvesting.

Various modifications the vehicle and apparatus of the invention will be readily apparent to those skilled in the art and are included within the scope of the invention as defined by the appended claims.

Claims

CLAIMS:

1. A vehicle comprising:

a flywheel having a spin axis,

a drive system adapted to rotate the flywheel about the spin axis,

2. A vehicle according to claim 1 further comprising a storage device for storing power generated by the power take-off device, and wherein the propulsion system is coupled, directly or indirectly, to the storage device to receive stored power therefrom.

3. A vehicle according to claim 1 or claim 2 wherein the precession axis is substantially vertical and the spin axis is substantially horizontal.

4. A vehicle according to any foregoing claim wherein the spin axis substantially coincides with at least one of the roll motion, pitch motion and yaw motion axes of the vehicle.

5. A vehicle according to claim 4 wherein the spin axis substantially coincides with at least one of the roll motion and pitch motion axes of the vehicle.

6. A vehicle according to any foregoing claim wherein an intersection of the precession and spin axes substantially coincides with an intersection of at least two of the roll motion, pitch motion and yaw motion axes of the vehicle.

7. A vehicle according to claim 6 wherein an intersection of the precession and spin axes substantially coincides with an intersection of all of the roll motion, pitch motion and yaw motion axes of the vehicle.

8. A vehicle according to any foregoing claim wherein the drive system is adapted to rotate the flywheel about the spin axis at a spin rate of from 1000 to 50000 revolutions per minute, optionally from 5000 to 20000 revolutions per minute, further optionally about 10000 revolutions per minute.

9. A vehicle according to any foregoing claim wherein the drive system is adapted to rotate the flywheel about the spin axis at a constant spin rate.

10. A vehicle according to any one of claims 1 to 8 wherein the drive system is adapted to rotate the flywheel about the spin axis at a variable spin rate.

1 1. A vehicle according to any foregoing claim wherein the mechanism is adapted linearly to damp any oscillatory and rotational motion of the gimbal support about the precession axis.

12. A vehicle according to any one of claims 1 to 1 1 wherein the mechanism is adapted non-1 inearly to damp any oscillatory and rotational motion of the gimbal support about the precession axis.

13. A vehicle according to any foregoing claim further comprising an electrical generator system comprised in or coupled to the power take-off device.

14. A vehicle according to claim 13 when appendant on claim 2 wherein the electrical generator system is coupled to the storage device which is adapted for storing electrical power, and wherein the propulsion system is adapted to be driven by electrical power.

15. A vehicle according to claim 2 or any one of claims 3 to 13 when appendant on claim 2 wherein the storage device is adapted for storing kinetic energy.

16. A vehicle according to any foregoing claim wherein the mechanism is a hydraulic mechanism.

17. A vehicle according to any foregoing claim which is an autonomous underwater vehicle and the gyroscopic system is adapted to cause precession rotation about the precession axis when the vehicle moves by at least one of roll motion, pitch motion and yaw motion as a result of wave or other excitation on an exterior of the autonomous underwater vehicle.

18. A vehicle according to any foregoing claim which is a manned or unmanned submarine comprising a substantially cylindrical elongate hull.

19. A vehicle according to any foregoing claim further comprising a first control system adapted to control at least one of the damping of the precession rotation of the gimbal support and the rotation speed of the flywheel about the spin axis to maximise the power generated in the power take-off device.

20. A vehicle according to any foregoing claim further comprising a second control system adapted to control at least one of the damping of the precession rotation of the gimbal support and the rotation speed of the flywheel about the spin axis to control at least one of the roll motion, pitch motion and yaw motion of the vehicle.

21. A method of propulsing a vehicle, the vehicle having mounting therein a gyroscopic system comprising a flywheel having a spin axis, a drive system adapted to rotate the flywheel about the spin axis, and a gimbal support in which the flywheel is rotatably mounted for rotation about the spin axis, the gimbal support being rotatably mounted to a fixed base in the vehicle for precession rotation about a precession axis which is orthogonal to the spin axis of the flywheel, the method comprising the steps of:

22. A method according to claim 21 wherein the vehicle is an autonomous underwater vehicle, in step (b) when the autonomous underwater vehicle moves by at least one of roll motion, pitch motion and yaw motion as a result of wave or other excitation on an exterior of the autonomous underwater vehicle, that motion causes precession rotation about the precession axis, and the precession rotation is damped to generate power in a power take-off device coupled to the gimbal support.

23. A method according to claim 22 wherein steps (a) and (b) are carried out when the autonomous underwater vehicle is at the surface of a body of water and step (c) is carried out at least partly when the autonomous underwater vehicle is submerged beneath the surface of the body of water or at least partly when the autonomous underwater vehicle is at the surface of a body of water.

24. A method according to claim 22 or claim 23 wherein steps (a) and (b) are carried out when the autonomous underwater vehicle is in turbulent water and step (c) is carried out at least partly when the autonomous underwater vehicle is submerged beneath the surface of the body of water or at least partly when the autonomous underwater vehicle is at the surface of a body of water.

25. A method according to any one of claims 21 to 24 wherein the precession axis is substantially vertical and the spin axis is substantially horizontal.

26. A method according to any one of claims 21 to 25 wherein the spin axis substantially coincides with at least one of the roll motion, pitch motion and yaw motion axes of the vehicle.

27. A method according to claim 26 wherein the spin axis substantially coincides with at least one of the roll motion and pitch motion axes of the vehicle.

28. A method according to any one of claims 21 to 27 wherein an intersection of the precession and spin axes substantially coincides with an intersection of at least two of the roll motion, pitch motion and yaw motion axes of the vehicle.

29. A method according to claim 28 wherein an intersection of the precession and spin axes substantially coincides with an intersection of all of the roll motion, pitch motion and yaw motion axes of the vehicle.

30. A method according to any one of claims 21 to 29 wherein the flywheel is rotated about the spin axis at a spin rate of from 1000 to 50000 revolutions per minute, optionally from 5000 to 20000 revolutions per minute, further optionally about 10000 revolutions per minute.

31. A method according to any one of claims 21 to 30 wherein the drive system is adapted to rotate the flywheel about the spin axis at a constant spin rate.

32. A method according to any one of claims 21 to 30 wherein the drive system is adapted to rotate the flywheel about the spin axis at a variable spin rate.

33. A method according to any one of claims 21 to 32 wherein the damping linearly damps any oscillatory and rotational motion of the gimbal support about the precession axis.

34. A method according to any one of claims 21 to 32 wherein the damping non- linearly damps any oscillatory and rotational motion of the gimbal support about the precession axis.

35. A method according to any one of claims 21 to 34 further comprising the step of actively damping the oscillatory and rotational motion of the gimbal support about the precession axis.

36. A method according to any one of claims 21 to 35 further comprising the step, between steps (b) and (c) of:

(d) storing power generated by the power take-off device; and

step (c) uses the stored power.

37. A method according to any one of claims 21 to 36 wherein the precession rotation generates electrical power in an electrical generator system comprised in or coupled to the power take-off device.

38. A method according to claim 37 wherein the propulsion system is driven by electrical power.

39. A method according to claim 38 when appendant on claim 36 wherein the electrical power is stored in step (d).

40. A method according to claim 36 wherein the precession rotation generates power in the form of kinetic energy which is stored in step (d).

41. A method according to claim 40 wherein the kinetic energy is stored in a second flywheel.

42. A method according to claim 41 wherein the kinetic energy is selectively stored in or outputted from the second flywheel dependent upon input variables associated with a demand for propulsion and/or gyroscopic stability control of the vehicle.

43. A method according to any one of claims 21 to 42 wherein the damping comprises hydraulic damping.

44. A method according to any one of claims 22 to 24 wherein the autonomous underwater vehicle is a manned or unmanned submarine comprising a substantially cylindrical elongate hull.