GB2508400A

GB2508400A - Gyroscopic system with power generation

Info

Publication number: GB2508400A
Application number: GB1221587.7A
Authority: GB
Inventors: Nicholas Charles Townsend; Ramanand Ajit Shenoi
Original assignee: University of Southampton
Current assignee: University of Southampton
Priority date: 2012-11-30
Filing date: 2012-11-30
Publication date: 2014-06-04
Anticipated expiration: 2032-11-30
Also published as: WO2014083044A1; GB2508400B

Abstract

A gyroscopic system comprising: a drive system 18 adapted to rotate a flywheel 14 about a spin axis S, a gimbal support 12 in which the flywheel is mounted for rotation about the spin axis, the gimbal support being rotatably mounted to a fixed base for precession rotation about an axis V orthogonal to the spin axis of the flywheel, a power take-off device 22 coupled to the gimbal support comprising a mechanism which damps the precession rotation to generate power in the power take-off device, and a controller 32, 34 for the mechanism for controlling the precession rotation of the gimbal support. The controller is adapted to receive an input variable related to an input mechanical impulse on the gyroscopic system causing precession rotation and to output a control parameter having a non-linear relationship with the input variable to control the precession rotation according to at least one precession response.

Description

GYROSCOPi C qy5p'J I he present inventron reates to a gyroscopic system, in partcuar a gyroscopic controllahk' moment generator adapted to be used as a motion control device for incorporation into a vehicle, thr exarnpk a marine vessel such as a boat or ship. The present invention thrther relates to a method of controlling the precession response of a gyroscopic system.

it is known in the art, for example from the Applicant's GBA247O96l, to provide a gyroscopic system to control or improve the motion characteristics of a vehicle, in particular marine vessels, subjected to such uncontrolled and undesirable movements. Gyrostabiliser systems generate stabilising moments entirely within the hull of a vessel without simply rdying on providing sufficient movable weight. Such gyrostabiliser systems are becoming of increased. interest in the marine vessel art, and are a reernerging solution.

A gyrostabiliser uses the inertial property of a rotating body or fiywhee to apply moments to a vehicle (or other object) to after 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 hod, rotating with the body but not spinning with the body, and a symmetrica' rotating body or flywheel in x and y axes, (i.e, i=I=l and:i can be expressed as; = !(th ULQ)+JJll (w, +) (1) M =i(cb +Qa).rLOJx(Wr+W) (2) M=LJth.±Lii) (3) where: M, M and M are, respectively, the moment acting about the x, y or a axis, I is the mass moment of inertia of the rotating body or flywheel, about the x or y axis, h. is the mass moment of inertia about the z axis, w, and w. are, respectively, the rate of rotation of the gyroscope about the x, y or a and th are, respectively, the angular acceleration of the gyroscope about the x, y or z axis, is the spin rate of the rotating body or flywheel, and 1j is the angular acceleration of the rotating body or flywheel.

When operating, the rotating body or flywheel within the gyroscope rotates about an axis, rliich itself is free to rotate. J}ierefture. in addition to the usua terms that accourt the moments when the rotating body or flywheel is not spinning. Equations. (2) and (3) indicate the existence of additionaL gyroacopic n.ionients, that act around the x and y axes ftc, 41 1:w.' and M = -i.v). These gvroscopic moments are used to apply stabi.Iising moments in gyrostabilisers.

Inn 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 gyrostahiliser 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 he damped by the provision of damping elements.

In another particular arrangement, known as active gyrostahi User system, the gyroscope is forced to rotate about its free axis, such rotation herein being known as nutation, resulting m a motioncontrolhng moment being generated about the ship4lxed axis of the gyroscope.

For both passive and active gyrostabiLisers the stabilising effect is dependent on; The massinoment-ofinertia 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 (y) and, The rate of rotation of the gyroscope about its free axis, ( oru, depending on axis definition).

The rate of rotation of the rotating body or flvwhed of the gyroscope about its free axis (w in a gyrostabiliser, must retain a phase relationship to the excitation.

In an active gyrostahiliser, where this rotation (w orw2) 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 gyrostahiliser systems. the gvroscopic 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 hut 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 timiting the stabilising moments tnat can he achieved.

It is also known for example from GB-A.-2470961, for the gyroscopic system to control the damping to enable energy to he retrieved from the gvroscopic system. En particular, a damper mechanism may be coupled to the gimbal support fOr the flywheel to damp the rotational motion of the gimbal support.

The oresent invention aims to provide a gyroscopic system adapted to provide a greater energy retrieval efficiency and effectiveness.

Accordingly, the present invention provides a gyrosconic system 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 rotatabi mounted for rotation about the spin axis, the gimbal support being rotatabl.y mounted to a fixed base for precession rotation about a precession axis which is orthogonal to the spin axis of the flywheel, a power take-off device coupled to the gimbal support, the power take-off device comprising a mechanism which daurips the precession rotation to generate power in the power taxe-ott. device, and a controller for the mechanism for controlling the precession rotation of the gimbal support, the controller being adapted (a) to receive an input variable related to an input mechanical impulse on the gyroscopic system causing precession rotation and Ib) to output a control parameter having a nonlinear relationship with the input variable to control the precession rotation according to at least one precession response.

In some embodiments, the precession response defined by the control parameter is a first precession response having substantially sinusoidal relationship for the precession angle with respect to time and has variable maximum precession angle between cycles.

In some embodiments, the precession response defined by the control parameter is a second precession response having a non-sinusoidal oscillatory relationship for the precession angle with respect to time. Optionally, the non-sinusoidal oscillatory relationship for the precession angle with respect to time has variable maximum precession angle between cycles and/or the non-sinusoidal oscillatory relationship for the precession angle with respect to time has at least two superposed frequencies when the input variable has a single input freqi.iency, in sonic embodiments, the precession response defined by the control parameter is a third precession response having a substantially random oscillatory relationship for the precession angle with respect to time. Optionally, the substantially random oscillatory relationship for the precession angle with respect to time has substantially random oscillatory frequency and/or the substantially random oscillatory relationship for the precession angle with respect to time has substantially random variable maximum precession angle between cycles.

in some embodiments, the precession response defined by the control parameter is a fourth precession response having a continuous rotation with a non-sinusoidal relationship for the precession angle with respect to time, Optionally, the continuous rotation is variable, random, non-linear or chaotic, In some embodiments, the controller is adapted to output the control parameter havin.g at least two precession responses which sequentially change with respect to time and/or the input variable. $

In some embodiments, the controuer is adapted to output the control parameter having the first, second third or fiiurth precession response an.d sequentially to change the first, second third or fourth precession response to a different first, second third or fourth precession response in response to a change in time and/or the input variable, In some embodiments, the at least one precession response controls damping of the precession rotation and/or controls power generated in the power takeoff device and/or controls motion of the fixed base and/or controls a nutation response of the gimbal support.

In some embodiments, the control parameter is adapted to damp the precession rotation of the gimbal support in response to input harmonic or noiFharmonic excitation moments or motions on the gyroscopic system and the angu!ar velocity of the precession rotation.

Optionally, in the absense of input excitation moments or motions the precession axis is substantially vertical and the spin axis is substantially horizontal, and the input excitation moments on the gyroscopic system are about a horizontal axis, Optionally, the input excitation moments or mouons have a frequency of from 0.1 to 5 l-Iertz, optionally from 0,1 to I Hertz.

In some embodiments, the controller is adapted to damp the precession rotation of the gimbal support in response to input harmonic or nonharmonie excitation moments or motions on the gyroscopic system and thc angular v&ocity of the precession rotation.

in some embodiments, the drive system is adapted to rotate the flywheel about the spin axis at a spin race of from 1000 to 50000 revolutions per minute, In some embodiments, the first drive system is adapted selectively to rotate the flywheel about the spin axis at a constant spin race or at a variable spin rate.

In some embodiments, the mechanism is a hydraulic mechanism.

In some embodiments, the gyroscopic system further comprises an electrical generator system comprised in or coupled to the power uakcoff device.

C

Optionally, the gyroscopic system ibrther comprises a storage device coupled to the electrical generator system which is adapted for storing electrical power.

In some embodiments, the gyroscopic system further comprises a storage device coupled to the power take-off device which is adapted for storing kinetic energy.

The present invention further provides a marine vessel having mounted therein the gyroscopic system according to the invention, the fixed base being fixed to the vessel.

In some embodiments, the marine vessel comprises a propulsion system which is directly or indirectly coupled 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 marine vessel, Optionally, the marine vessel is a manned or unmanned submarine comprising a substantially cylindrical elongate hull.

In some embodiments, the precession axis is substantially vertical and the spin axis is substantially horizontal.

In some embodiments, the spin axis substantially coincides with at least one of the roll motion, pitch motion and yaw motion axes of the vessel, optionally with at least one of the roll motion and pitch motion axes of the vessel.

In some embodiments, 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 vessel.

The present invention further provides a method of controlling the precession rotation of a gyroscopic system 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 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 gyroscopic system moves as a result of an input mechani al impulse on the gyroscopic system, that motion causes precession rotation of the gimbal support about the precession axis, (h) when the gyioscopie system moves as a result of an input mechanical impulse on the gyroscopic system, damping the precession rotation to generate power in a power take-off device coupled to the gimha support, and (c) controlling the precession rotation of the gimbal support by: (i) receiving an input variable related to the input mechanical impulse on the gyroscopic system causing precession rotation, and (ii) outputting a control parameter having a non-linear reationship with the input variable to control the precession rotation according to at least one precession response.

Further optional features and aspects of the present invention are defined in the dependent claims.

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 system in a vehicle in accordance with an embodiment of the present invention; Figure 3 is a schematic diagram of an autonomous underwater vehicle incorporating the gyroscopic stahiliser system of Figure 2 in accordance with another embodiment of the present invention; Figures 4(a) to 4e) illustrate a number of graphs showing the modelled relationship between precession angle and time for varying damping factors applied in a gyroscopic system in accordance with embodiments of the present invention; Figures 5(a) to 5(e) correspondingly illustrate a number of aphs showing the modelled relationship between precession angular velocity and precession angle for varying damping factors applied in a gyroscopic system in accordance with embodiments of the present invention; and / Figures 6(a) to 6(e) correspondingly illustrate a number of graphs showing the modelled relationship between instantaneous output power and precession angle for varying damping factors applied in a gyroscopic system in accordance with embodiments of the present invention.

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 hufl 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 shall 16 of the flywheel 14 being rotationally mounted in the gimbal support 12, A spin motor 18 is mounted to the shaft 1$ 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 he arranged, together with the spin motor 18, to spin in a selected one of two opposite rotational directions. The spin motor 1 8 comprises a drive system for rotating the flywheel 1 4 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 fixedy 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 gimba.l 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.

B

Thus, in the illustrated embodiment the precession axis is substantially vertical and the spm axis is substantially hori-ontal, In an alternative con.tiguraton of the gyroscopic system in the invention1 the base comprises two horizontafly spaced base elements and the gimbal support could he mounted to precess about a vertical axis.

Typically, the spin axis substantially coincides with at least one of the roil 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 vehice, more typically an intersection of all of the roil 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 roil motion, pitch motion and yaw motion.

in alternative embodiments, the gyroscopic system may comprise plural flywheel!gimbai support assemblies, either coupled together to a singk energy harvesting and power utilising system or independently operating to provide independent energy harvesting and utitisation.

A power take-off device 22 is coupled to the gimbal support 12, F he power take-off device 22 comprises a. switchable mechanism 22 which is selectively coupiable to the girnba.l support 12, directly or indirectly by one or both of the shafts 20, 20', controliably to damp any rotational precession rotation ofT the gimbal support 1 2. The mechanism is adapted inearly 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 ol' the precession rotation generates power in the power take-off device 22, The power take-otT device 22 may he 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 dectrica! power, and the propulsion ssten 24 is adapted to he driven by electrical power.

In one emhodment, 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 th 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 gyrostahiliser 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 rnorrieut.

The power take-off mechanism 22 may optionally he wholly or partly incorporated into the riutation motor or a controller therefor, for example by electromagnetic damping, arid 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. i'he gyroscopic system 2 is adapted to cause precession rotation about the precession axis V when the vessel 40 moves by at least one of roil 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.

Note that the X, Y and Z axes do not correspond to the correspondingly named axes in Figure 1.

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 1 2 and the rotation speed of the flywheel 14 about the spin axis to maximise the power generated in the power take-off device 22. In other words, the first control system 32 controls the gyroscopic system 2 selectively to provide an optimal power output, typically electrical power, for providing power to the vessel 40, for example to provide motive power andior to supply power to on-hoard equipment, such as sensors and other systems and subsystems. Furthermore, the gvroscopic system 2 thrther comprises a second control system 34 adapted to control at least one of the damping of the precession rotatjon of the gimbal support 1.2 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. n 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 aL 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 propuised 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 roil 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 he stored and the provision of motive power may use the sic red power.

in one embodiment, the precession rotation generates electrical power in the eiectrica.l 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' generatron is typically caried 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 p1y* hen the autonomous underwater vehicle is at the surface of the body of water.

In a typical cycle, the auionomous 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 propuised 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 osetilatory and rotational motion of the gimbal support about the precession axis may he actively damped to provide a gyroscopic stahihsing effect in the vehicle. The preferred embodiments of the present invention can provide a gyrostabiliser system which can he passively or actively damped, by manual selection or automatic control, and also a thrther active continuous notation mode is possible in which the gyrostahiliser flywheel is rotationally nutated in a continuous manner to produce opposing moments to the roil motion excitation moments.

The gyrostabiliser system may he 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.

As will he apparent from the foregoing, there is in some applications a need or desire for the power takeoff from the damping to be niaximised to permit effective and. efficient energy harvesting from input mechanical energy acting on the gyroscopic system.

A modelling and analysis of a single gimbal gyroscopic energy harvester damper mechanism shows that the instantaneous power P(t) absorbed by the damper due to the flywheel precession may be modelled as: P(t) B (32 where Bg represents a damping factor for the precession power takeoff from the damping and (3 represents the precession angular velocity.

When the gyroscopic system receives input iriechar.ucai impulses, the frequency of those inipuhes, referred to herein as the forcing frequency, can affect the response of the gyroscopic system with regard to the precession behaviour.

The effect of forcing frequency on the gyroscopic precession response to forced harmonic moments about the X axis shown in Figure 3 can he modelled, using the relationship above, to indicate that around resonance, when the body motions are greatest, the gyroscopic precession responses can become nonlinear.

In this aspect of the present invention, the second control system 34 controls the precession rotation of the gimbal support. The second control system 34 is adapted (a) to receive an input variable related to an input mechanical mpuise on the gyroscopic system causing precession rotation and (b) to output a control parameter having a non4inear relationship with the input variable to control the precession rotation according to at least one precession response.

In one application, the precession response defined by the control parameter is a first precession response having substantially sinusoidal relationship for the precession angle with respect to time and has variable maximum precession angle between cycles.

In another apnlication. the precession response defined by the control paraiTleter is a second.

precession response having a non-sinusoidal oscillatory relationship for the precession angle with respect to time, Typically, the non-sinusoidal oscillatory relationship for the precession angle with respect to time has variable maximum precession angle between cycles, and/or the non-sinusoidal oscillatory relationship for the precession angle with respect to time has at least iwo superposed frequencies when the input variable has a single input frequency.

In another application, the precession response defined by the control parameter is a third precession response having a substantially random oscillatory relationship for the precession angle with respect to time. Typically, the substantially random oscillatory relationship for the precession angk with respect to time has substantially random oscillatory frequency, and/or the substantially random osciLlatory relationship for the precession angle with respect to time has substantially random variable maximum precession angle between cycles.

In another application, the precession response defined by the control parameter is a fourth precession response having a continuous rotation with a non-sinusoidal relationship fix the precession angle with respect to Lime, Typically. the continuous rotation is variable, random.

non-linear or chaotic, in some embodiments, the second control system 34 is adapted to output the contr& parameter having at keast two precession responses which sequentially change with respect to time and/or the input variable.

In sonic embodiments, the second control system 34 is adapted to output the control parameter having the first, second third or fourth precession response and sequentially to change the first, second third or fourth precession response to a different first, second third or fourth precession response in response to a change in time and/or the input variable.

The at least one precession response may control damping of the precession rotation, and/or may contro power generated in the power takeoff device, and/or may control motion of the fixed base/and/or may control a nutation response of the gimbal support.

Accordingly, typically the control parameter is adapted to damp the precession rotation of the gimbal support in response to input hannonic or nonharmomc excitation moments or motions on the gyroscopic system and. the angular velocity of the precession rotation.

Typically, in. the absense of input excitation moments the precession axis is substantially vertical and the spin axis is substantially horizontal, and. the input excitation moments or motions on the gyroscopic system are about a horizontal axis.

The input excitation moments or motions typically have a frequency of from 0.1 to 5 1-Jertz, optionally from (LI to I Hertz.

Typically, the second control system 34 is adapted to damp the precession rotation of the gimbal support in response to input harmonic or non-harmonic excitation moments or motions on the cyroscopic system and the angular velocity of: the precession rotation.

in these sppitcations, providing non-linear relationship between the input variable and the output contro parameter constitutes a development from single frequency sinusoidal, in this specification called "regular", gyroscopic precession to nonlinear gvroscopic precession. as illustrated in Figure 4, Figure 5 and Figure 6, Figures 4 and 5 represent the calculated outputs and responses for various control and input variables. In particular, for each calculation the values of: Bg representing the damping factor; the rotational speed of the flywheel and the frequency W: of the input mechanical imputses, for example wave energy, causing rotation about a rofl motion axis X, are provided.

Typically with greater gyroscopic damping providing greater damping resistance a single frequency sinusoidal gyroscopic response can be expected, The input variable related to an input mechanical impulse on the gyroscopic system causes precession rotation and the resultant precession damping response has a linear relationship with the input variaHe, Figure 4 (a) shows the relationship between the precession angle () and time for a linear damping relationship. This was modelled with a high damping factor of 300Nm.s to represent the greater precession damping, a rotational speed of the flywheel at 12,000 rpm and a frequency co of the input mechanical impulses of 0.2 Hz. The precession angle shows a single frequency sinusoidal response with respect to time. Figure 5 (a) shows the relationship between the precession angular velocity () and precession angle () time for a linear damping relationship. There is a circular plot of the precession angular velocity () versus the precession angle (p).

In contrast, with lower gyroscopic damping, nonlinear gyroscopic motion responses can be expected. Figure 4 (h) shows the relationship between the precession angle and. time for the initial onset of nonlinear gyroscopic precession, which appears to begin with a period doubling, identifiable by the lower frequency component and distinctive time history. This was modelled with a lower damping factor of 250Nm,s to represent the reduced precession damping. a rotational speed of the flywheel at l2,000 rpm and a frequency io of the input mechanical impulses of 0.2 i-la. Figure 5 (h) shows the relationship between the precession angular velocity () and precession angle () time for the initial nonlinear damping relationship, showing the period doubling relationship, and a noncircuiar plot of the precession angular velocity (*) versus the precession angle ([i).

With further damping redu.cdons the period doubling response can he exaggerated and oscillations can deve'op, as shown in Figures 4 (c) and 4(d), and 5(c) and 5(d). with distinctive precession angular velocity (3) versus the precession angle (D) and, at times, relatively large angular velocities. For Figures 4(c) and 5(c) this was modelled with a clamping factor of 200Nm.s to represent the reduced precession damping, a rotational speed of the flywheel at 12,000 rpm and a frequency o of the input mechanical impulses of 0.2 Hz.

For Figures 4(d) and 5(d) this was modelled with a damping factor of I5ONm.s to represent the reduced precession damping, a rotationa speed of the flywheel at 12,000 rpm and a frequency o of the input mechanical impulses of 0.2 Hz. The angular velocity for some of the precession cyc]e is significantly increased as compared to the single frequency sinusoidal response of Figure 4(a). Such large angular velocities as shown in Figure 5 (c) and (d) imply that relatively large instantaneous powers are available for take-off from the rotating gimbal structure by the damping mechanism in an energy harvesting mode.

For Figures 4e) and 5(e) this was modelled with a damning factor of lOONm.s to represent the reduced precession damping, a rotational speed of the flywheel at 12,000 rpm and a frequency co of the input mechanical impulses of 0.2 Hz. With certain damping and fi'equency combinations the period doubling motion can become a continuous oscillation, as shown in Figure 5(e), spanning two workspace' regions, i.e., at 90° to +90 and +900 to +270°, or greater than two workspace regions. The motion can thrther develop into a continuous rotation& precession, which implies that a continuous power output is achievable.

It is to be noted that in any given gyroscopic system and at any given input excitation frequency, the lower the damping the greater the precession, which may cause the onset of irregular motion at lower damping. in addition, if the input excitation frequency changes so as to move closer to a. resonance frequency of the system having a given damping, this may also cause the onset of irregular motion.

The power characteristics of the system, subjected to forced harmonic moment excitations about the X axis, are illustrated in Figure 6. Figure 6 shows the relationship between instantaneous output power and. precession angle. Similar to the precession responses of Figures 4 and 5. the instantaneous powers of Figure 6 were found to exhibit characteristic responses.

Figure 6(a) corresponds to Figures 4(a) and 5(a) and shows the power output for a single frequency sinusoidal linear output, There i.s a single peak at a precession angle of 0°. Figure 6(h) corresponds to Figures 4(b) and 5(h) and shows the power output for a nonlinear output.

There is a wider single peak at a precession angle of 0°. Figure 6(c) corresponds to Figures 4(c) and 5(c) and shows the power output for a nonlinear output showing period doubling, the maximum instantaneous power predominantly occurring at precession angles of Q° (and/or multiples of +II 300), Figure 6(d) corresponds to Figures 4(d) and 5(d) and shows the power output for a nonlinear output showing a similar relationship as for Figure 6(c). Figure 6(e) corresponds to Figures 4(e) and 5(e) arid shows the power output for a nonlinear output showing continuous oscillation spanning several workspace' regions, the maximum instantaneous power predominantly occurring at precession angles of 00 (and/or multiples of ±/i 80). As described above, with certain damping and frec.uency combinations greater than two workspac& regions may be provided.

It is to be noted from Figures 6(a) to (d) that provided nonlinear precession motions are allowed to develop, greater precession rates and instantaneous powers are available. The spin rate and damping, 3g. are matched br a given body, flywheel design (mass moment of inertia) and forced excitation (frequency and magnitude). At low spin rates where the gyroscopic response is regular, a decrease in damping yields a greater precession response and greater power capture. However, with greater spin rates, where the gyroseopic responses can become nonlinear an optimal damping emerges.

These modelled results provide a valuable insight into the behaviour and performance of a single gimbal gyroscopic energy harvester, including nonlinear responses and show that by controllably damping the precession rotation of the gimbal support, so that when the controller receives an input variable related to an input mechanical impulse on the gyroscopic system causing precession rotation and outputs a control parameter having a nonlinear relationship with the input variable to control the damping of the precession rotation, the output takeoff power can be increased and optionally maximised.

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 gyroscopic system 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 for precession rotation about a precession axis which is orthogonal to the spin axis of the flywheel, a power take-off device coupled to the gimbal support, the power takc-off device comprising a mechanism which damps the precession rotation to generate power in the power take-off device, and a controller for the mechanism for controlling the precession rotation of the gimbal support, the controller being adapted (a) to receive an input variable related to an input mechanical impulse on the gyroscopic system causing precession rotation and (b) to output a control parameter having a non-linear relationship with the input variable to control thc precession rotation according to at least one precession response.
2. A gyroscopic system according to claim 1 wherein the precession response defined by the control parameter is a first precession response having substantially sinusoidal relationship for the precession angle with respect to time and has variable maximum precession angle between cycles.
3. A gyroscopic system according to claim 1 wherein the precession response defined by the control parameter is a second precession response having a non-sinusoidal oscillatory relationship for the precession angle with respect to time.
4. A gyroscopic system according to claim 3 wherein the non-sinusoidal oscillatory relationship for the precession angle with respect to time has variable maximum precession angle between cycles.
5. A gyroscopic system according to claim 3 or claim 4 wherein the non-sinusoidal oscillatory relationship for the precession angle with respect to time has at least two superposed frequencies when the input variable has a single input frequency.
6. A gyroscopic system according to claim I wherein the precession response defined by the control parameter is a third precession response having a substantially random oscillatory relationship for the precession angle with respect to time.
7. A gyroscopic system according to claim 6 wherein the substantially random oscillatory relationship for the precession angle with respect to time has substantially random oscillatory frequency.
8. A gyroscopic system according to claim 6 or claim 7 wherein the substantially random oscillatory relationship for the precession angle with respect to time has substantially random variable maximum precession angle between cycles.
9. A gyroscopic system according to claim 1 wherein the precession response defined by the control parameter is a fourth precession response having a continuous rotation with a non-sinusoidal relationship for the precession angle with respect to time.
10. A gyroscopic system according to claim 9 wherein the continuous rotation is variable, random, non-linear or chaotic.
11. A gyroscopic system according to any foregoing claim wherein the controller is adapted to output the control parameter having at least two precession responses which sequentially change with respect to time and/or the input variable.
12. A gyroscopic system according to any one of claims 2 to 10 wherein the controller is adapted to output the control parameter having the first, second third or fourth precession response and sequentially to change the first, second third or fourth precession response to a different first, second third or fourth precession response in response to a change in time and/or the input variable.
13. A gyroscopic system according to any foregoing claim wherein the at least one precession response controls damping of the precession rotation.
14. A gyroscopic system according to any foregoing claim wherein the at least one precession response controls power generated in the power take-off device.
15. A gyroscopic system according to any foregoing claim wherein the at least one precession response controls motion of the fixed base.
16. A gyroscopic system according to any foregoing claim wherein the at least one precession response controls a nutation response of the gimbal support.
17. A gyroscopic system according to any foregoing claim wherein the control parameter is adapted to damp the precession rotation of the gimbal support in response to input harmonic or non-harmonic excitation moments or motions on the gyroscopic system and the angular velocity of the precession rotation.
18 A gyroscopic system according to claim 17 wherein in the absense of input excitation moments or motions the precession axis is substantially vertical and the spin axis is substantially horizontal, and the input excitation moments on the gyroscopic system are about a horizontal axis.
19. A gyroscopic system according to claim 17 or claim 18 wherein the input excitation moments or motions have a frequency of from 0.1 to S Hertz, optionally from 0.1 to 1 Hertz.
20. A gyroscopic system according to any foregoing claim wherein the controller is adapted to damp the precession rotation of the gimbal support in response to input harmonic or non-harmonic excitation moments or motions on the gyroscopic system and the angular velocity of the precession rotation.
21. A gyroscopic system 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.
22. A gyroseopie system according to any foregoing claim wherein the first drive system is adapted selectively to rotate the flywheel about the spin axis at a constant spin rate or at a variable spin rate.
23. A gyroscopic system according to any foregoing claim wherein the mechanism is a hydraulic mechanism.
24. A gyroscopic system according to any foregoing claim further comprising an electrical generator system comprised in or coupled to the power take-off device.
25. A gyroscopic system according to claim 24 further comprising a storage device coupled to the electrical generator system which is adapted for storing electrical power.
26. A gyroscopic system according to any one of claims 1 to 24 further comprising a storage device coupled to the power take-off device which is adapted for storing kinetic energy.
27. A marine vessel having mounted therein the gyroscopic system according to any foregoing claim, the fixed base being fixed to the vessel.
28. A marine vessel according to claim 27 comprising a propulsion system which is directly or indirectly coupled 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 marine vessel.
29. A marine vessel according to claim 28 which is a manned or unmanned submarine comprising a substantially cylindrical elongate hull
30. A marine vessel according to any one of claims 28 to 29 wherein the precession axis is substantially vertical and the spin axis is substantially horizontal.
31. A marine vessel according to any one of claims 28 Lu 30 whcrein the spin axis substantially coincides with at least one of the roll motion, pitch motion and yaw motion axes of the vessel.
32. A marine vessel according to claim 31 wherein the spin axis substantially coincides with at least one of the roll motion and pitch motion axes of the vessel.
33. A marine vessel according to claim 31 or claim 32 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 vessel.
34. A method of controlling the precession rotation of a gyroscopic system 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 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 gyroscopic system moves as a result of an input mechanical impulse on the gyroscopic system, that motion causes precession rotation of the gimbal support about the precession axis, (b) when the gyroscopic system moves as a result of an input mechanical impulse on the gyroscopic system, damping the precession rotation to generate power in a power take-off device coupled to the gimbal support, and (c) controlling the precession rotation of the gimbal support by: (i) receiving an input variable related to the input mechanical impulse on the gyroscopic system causing precession rotation, and (ii) outputting a control parameter having a non-linear relationship with the input variable to control the precession rotation according to at least one precession response.
35. A method according to claim 34 wherein the precession response defined by the control parameter is a first precession response having substantially sinusoidal relationship for the precession angle with respect to time and has variable maximum precession angle between cycles.
36. A method according to claim 34 wherein the precession response defined by the control parameter is a second precession response having a non-sinusoidal oscillatory relationship for the precession angle with respect to time.
37. A method according to claim 36 wherein the non-sinusoidal oscillatory relationship for the precession angle with respect to time has variable maximum precession angle between cycles.
38. A method according to claim 36 or claim 37 wherein the non-sinusoidal oscillatory relationship for the precession angle with respect to time has at least two superposed frequencies when the input variable has a single input frequency.
39. A method according to claim 34 wherein the precession response defined by the control parameter is a third precession responsc having a substantially random oscillatory relationship for the precession angle with respect to time.
40. A method according to claim 39 wherein the substantially random oscillatory relationship for the precession angle with respect to time has substantially random oscillatory frequency.
41. A method according to claim 39 or claim 40 wherein the substantially random oscillatory relationship for the precession angle with respect to time has substantially random variable maximum precession angle between cycles.
42. A method according to claim 34 wherein the precession response defined by the control parameter is a fourth precession response having a continuous rotation with a non-sinusoidal relationship for the precession angle with respect to time.
43. A method according to claim 42 wherein the continuous rotation is variable, random, non-linear or chaotic.
44. A method according to any one of claims 34 to 43 wherein the control parameter has at least two precession responses which sequentially change with respect to time andlor the input variable.
45. A method according to any one of claims 35 to 43 wherein the control parameter has the first, second third or fourth precession response and sequentially changes the first, second third or fourth precession response to a different first, second third or fourth precession response in response to a change in time and/or the input variable.
46. A method according to any one of claims 34 to 45 wherein the at least one precession response controls damping of the precession rotation.
47. A method according to any one of claims 34 to 46 wherein the at least one precession response controls power generated in the power take-off device.
48. A method according to any one of claims 34 to 47 wherein the at least one precession response controls motion of the fixed base.
49. A method according to any one of claims 34 to 48 wherein the at least one precession response controls a nutation response of the gimbal support.
50. A method according to any one of claims 34 to 49 wherein the control parameter is adapted to damp the precession rotation of the gimbal support in response to input harmonic or non-harmonic excitation moments or motions on the gyroscopic system and the angular velocity of the precession rotation.51 A method according to claim 50 wherein in the absense of input excitation moments or motions the precession axis is substantially vertical and the spin axis is substantially horizontal, and the input excitation moments on the gyroscopic system are about a horizontal axis.52. A method according to claim 50 or claim 51 wherein the input excitation moments or motions have a frequency of from 0.1 to S Hertz, optionally from 0.1 to I Hertz.53. A method according to any one of claims 34 to 52 wherein the control parameter damps the precession rotation of the gimbal support in response to input harmonic or non-harmonic excitation moments or motions on the gyroseopic system and the angular velocity of the precession rotation.54. A method according to any one of claims 34 to 53 wherein in step (a) the flywheel is rotated about the spin axis at a spin rate of from 1000 to 50000 revolutions per minute.55. A method according to any one of claims 34 to 54 wherein in step (a) the flywheel is rotated about the spin axis at a constant spin rate or at a variable spin rate.56. A method according to any one of claims 34 to 55 wherein the power-take off is hydraulic.57. A method according to any one of claims 34 to 43 farther comprising generating electrical power in an electrical generator system comprised in or coupled to the power take-off device.58. A method according to claim 57 further comprising storing electrical power in a storage device coupled to the electrical generator system.59. A method according to any one of claims 34 to 57 further comprising storing kinetic energy in a storage device coupled to the power take-off device.60. A method according to any one of claims 34 to 59 wherein the gyroscopic system is mounted in a marine vessel, the fixed base being fixed to the vessel, and the input mechanical impulse causes at least one of roll motion, pitch motion and yaw motion of the marine vessel.61. A method according to claim 60 wherein the marine vessel comprises a propulsion system which is directly or indirectly coupled to the power-take off device to receive generated by the power take-off device which is converted to motive power to propulse the marine vessel.62. A method according to claim 61 wherein the marine vessel is a manned or unmanned submarine comprising a substantially cylindrical elongate hull.63. A method according to any one of claims 60 to 62 wherein the precession axis is substantially vertical and the spin axis is substantially horizontal.64. A method according to any one of claims 60 to 63 wherein the spin axis substantially coincides with at least one of the roll motion, pitch motion and yaw motion axes of the vessel.65. A method according to claim 64 wherein the spin axis substantially coincides with at least one of the roll motion and pitch motion axes of the vessel, 66. A method according to claim 64 or claim 65 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 vessel,