Vibration Energy Harvesting Device

TECHNOLOGICAL FIELD

Embodiments of the present disclosure relate to a vibration energy harvesting device. Some relate to a vibration energy harvesting device configured to harvest energy from oscillations in a rotor’s angular speed and some relate to the use of the harvested energy to power a sensing system.

BACKGROUND

Rotors (such as shafts) rotate when subjected to torque. When the torque is not entirely constant and includes perturbations around a mean value, it causes torsional vibration. It is known to mount absorbers to the rotors to counteract torsional vibrations and reduce the amplitude of oscillation in the rotor’s angular speeds caused by them.

BRIEF SUMMARY

According to various, but not necessarily all, embodiments there is provided examples as claimed in the appended claims.

According to various, but not necessarily all, embodiments there is provided a vibration energy harvesting device for converting energy of targeted order oscillations in a rotor’s angular speed into electrical energy, the vibration energy harvesting device comprising: a carrier supporting at least one conductive coil and configured to be mounted to, and thereby rotate at a same angular speed as, the rotor; and a pendulum formed from an inertial mass suspended from the carrier such that the inertial mass can oscillate along a substantially tautochronic path which is tuned to the targeted order. The inertial mass comprises at least one permanent magnet, the motion of which, relative to the at least one conductive coil, induces a voltage in the at least one conductive coil. According to various, but not necessarily all, embodiments there is provided a vibration energy harvesting device for converting energy of targeted order oscillations in a rotor’s angular speed into electrical energy, the vibration energy harvesting device comprising: a carrier supporting at least one permanent magnet and configured to be mounted to, and thereby rotate at a same angular speed as, the rotor; and a pendulum formed from an inertial mass suspended from the carrier such that the inertial mass can oscillate along a substantially tautochronic path which is tuned to the targeted order. The inertial mass comprises at least one conductive coil, the motion of which, relative to the at least one permanent magnet, induces a voltage in the at least one conductive coil.

The following portion of this ‘Brief Summary’ section, describes various features that may be features of any of the embodiments described in the foregoing portion of the ‘Brief Summary’ section. The description of a function should additionally be considered to also disclose any means suitable for performing that function.

The substantially tautochronic path may be comprised in a plane orthogonal to the rotor’s axis of rotation.

The vibration energy harvesting device may be configured to be mounted to the rotor such that an effective pivot of the pendulum is radially offset from the rotor’s axis of rotation.

The inertial mass may be suspended on one or more rollers running on a curved track in the inertial mass and/or a curved track in the carrier.

The curved track in the inertial mass may be curved in an opposite direction to the curved track in the carrier.

The inertial mass may be suspended on twin rollers running on twin sets of curved tracks, displaced from one another in a direction perpendicular to an axis around which the at least one conductive coil is wound. Magnetic poles of the at least one permanent magnet may be coplanar and lie in a plane which is substantially orthogonal to an axis around which the at least one conductive coil is wound.

The vibration energy harvesting device may be configured to be mounted to the rotor such that an axis around which at least one conductive coil is wound is perpendicular to the rotor’s axis of rotation.

The vibration energy harvesting device may be configured to be mounted to the rotor such that the at least one conductive coil is radially offset from the rotor’s axis of rotation.

The vibration energy harvesting device may comprise one or more further pendulums tuned respectively to one or more further targeted order oscillations in the rotor’s angular speed and suspended from the carrier.

According to various, but not necessarily all, embodiments there is provided a sensing system comprising one or more sensors, the vibration energy harvesting device described in the foregoing portion of the ‘Brief Summary’ section, and circuitry configured to operate the one or more sensors using the electrical energy from the vibration energy harvesting device.

The sensing system may comprise one or more wireless transceivers configured to transmit sensor data and/or data produced by processing of the sensor data, wherein the circuitry is configured to operate the one or more wireless transceivers using the electrical energy from the vibration energy harvesting device.

The circuitry may comprise an alternating to direct current convertor.

The circuitry may comprise: an electrical energy storage means configured to be charged by the electrical energy from the vibration energy harvesting device and to release stored energy to enable operation of the one or more sensors; and a controller configured to manage the charging and discharging of the electrical energy storage means. According to various, but not necessarily all, embodiments there is provided a machine comprising the vibration energy harvesting device or the sensing system described in the foregoing portion of the ‘Brief Summary’ section. The machine comprises a rotor.

The machine may comprise a torque source configured to drive rotation of the rotor.

One or more inaccessible electronic components may be comprised within the machine, the one or more inaccessible electronic components being configured to received electrical energy from the vibration energy harvesting device.

According to various, but not necessarily all, embodiments there is provided a vehicle comprising the vibration energy harvesting device or the sensing system described in the foregoing portion of the ‘Brief Summary’ section. The vehicle comprises a driveshaft and the vibration energy harvesting device is configured to convert energy of targeted order oscillations in the driveshaft’s speed into electrical energy.

The vehicle may comprise a prime mover configured to drive rotation of the driveshaft.

BRIEF DESCRIPTION

Some examples will now be described with reference to the accompanying drawings in which:

FIG 1 shows an example of a vibration energy harvesting device described herein; FIG 2 shows lumped parameter model of an example described herein;

FIGS 3A to 3D show another example of a vibration energy harvesting device described herein;

FIG 4 shows an example of another vibration energy harvesting device described herein;

FIGS 5A to 5D show another example of a vibration energy harvesting device described herein;

FIG 6 shows an example of a sensing system described herein; and FIG 7 shows an example of a machine described herein.

DETAILED DESCRIPTION FIG 1 schematically depicts a vibration energy harvesting device 1 for harvesting energy from oscillations in an angular speed of a rotor 3. In particular, the vibration energy harvesting device 1 is configured to convert energy of targeted order oscillations in a rotor’s angular speed into electrical energy.

Although the vibration energy harvesting device 1 may harvest energy most effectively from targeted order oscillations in a rotor’s angular speed, it will be appreciated that it may harvest energy from other orders as well.

The vibrational energy harvesting device 1 comprises a pendulum 17, the inertial mass 13 of which comprises a permanent magnet 21. The pendulum is arranged to move relative to a conductive coil 9, under the influence of oscillations in the angular speed of the rotor 3, and to thereby induce a voltage in the conductive coil 9.

A rotor 3 is a component that rotates about an axis (the axis of rotation 5). The rotor 3 may be an elongate member, a shaft, an axle, or the like.

The rotor 3 may be subject to speed fluctuations. For example, non-constant forces may be involved in the generation or transmission of the torque which drives the rotation of rotor 3, creating torsional vibrations. Consequently, the rotor 3 may be subjected to oscillating torque comprising single-order or multiple-order harmonics. This, in turn, causes the rotor’s angular speed to oscillate about a mean angular speed.

Subjected to oscillating torque comprising single-order or multiple-order harmonics, the oscillations in the rotor’s speed occur at orders of (that is, frequencies which are multiples of) the mean angular speed of the rotor 3. If the rotor 3 rotates faster, the frequency of the oscillations in its speed increases and if the rotor 3 rotates slower, the frequency of the oscillations in its speed decreases.

Targeted order oscillations in the rotor’s angular speed are oscillations in a rotor’s angular speed at frequencies which are a targeted multiple of the rotor’s angular speed. Where the targeted order is the Nth order, the targeted oscillations have a frequency of N times the rotor’s angular speed. The targeted order may be the order of oscillations in the torque to which the rotor 3 is subjected. For example, the combustion stroke of a four-stroke engine produces an acceleration in the angular speed of the crankshaft (a rotor). Since the combustion stroke occurs once every two rotations of the crankshaft, for a single-cylinder four- stroke engine, the torque undergoes half an oscillation cycle per rotation of the crankshaft. Thus, the targeted order may be a half. If the engine comprises multiple cylinders, then the number of combustion strokes occurring per rotation of the crankshaft increases. There will be as many combustion strokes occurring over the course of two rotations of the crankshaft as there are cylinders. Consequently, the targeted order for a rotor 3 subjected to torque generated by a multi-cylinder four- stroke engine may be half of the number of cylinders.

The vibration energy harvesting device 1 comprises a carrier 7 which is configured to be mounted to, and thereby rotate at a same angular speed as, the rotor 3. For example, the carrier 7 can be mounted to the rotor 3 using press fitting, compression fit, set screws, or any other suitable means. The carrier 7 provides a base for other components of the vibration energy harvesting device 1 such that these other components need not be mounted separately or directly to the rotor 3 and can instead be operationally coupled to the rotor 3 via the carrier 7. The carrier 7 is configured to transmit the rotor’s angular speed, and oscillations in the same, to other components of the vibration energy harvesting device 1. The carrier 7 may be a rigid body.

The carrier 7 supports at least one conductive coil 9. In the following, reference is made to only a single conductive coil 9 but it is to be appreciated that multiple conductive coils 9 can be supported by the carrier 7. Each conductive coil 9 can comprise a single or a plurality of turns. In supporting the conductive coil 9, there is no movement between the carrier 7 and the conductive coil 9. The conductive coil 9 is fixed to the carrier 7. Accordingly, the conductive coil 9 is rotated about the axis of rotation 5 at the same angular speed as the rotor 3 and experiences the same oscillations in the angular speed.

In some examples, the carrier 7 supports the conductive coil 9 in a position offset from the axis of rotation 5. As depicted in FIG 1 , the conductive coil 9 is radially offset from the rotor’s axis of rotation 5 (and the rotor 3) when the vibration energy harvesting device 1 is mounted to the rotor 3. The axis 11 about which the conductive coil 9 is wound can be perpendicular to the rotor’s axis of rotation 5 when the vibration energy harvesting device 1 is mounted to the rotor 3. The axis 11 about which the conductive coil 9 is wound can be aligned along a radial direction from the axis of rotation 5. It is, however, to be appreciated that this need not be the case in all examples of the vibration energy harvesting device 1. For example, the axis 11 about which the conductive coil 9 is wound can be aligned parallel with the axis of rotation 5, nevertheless at a position radially offset from the rotor’s axis of rotation 5. More generally, the axis 11 about which the conductive coil 9 is wound can have any orientation relative to the axis of rotation 5 which enables a suitable change in the magnetic flux enclosed by the conductive coil 9 as a result of the motion of the permanent magnet 21 comprised in the inertial mass. A suitable change may be any change at all or may be a change which produces, in the conductive coil 9, a voltage suitable for the application in which the vibration energy harvesting device 1 is used.

The inertial mass 13 is suspended from the carrier 7. The inertial mass 13 may be suspended from one or more points. In contrast to the support for the conductive coil 9, the suspension of the inertial mass 13 does not prevent movement between the carrier 7 and the inertial mass 13. The means of suspension is a mechanical coupling which enables at least a swinging motion to be effected as between the inertial mass 13 and the carrier 7 (and thus also the rotor 3 and conductive coil 9). The effective pivot 15 for the swinging motion may coincide with the point from which the inertial mass 13 is suspended or, if the inertial mass 13 is suspended from the carrier 7 at a plurality of points, the effective pivot 15 may not coincide with the points from which the inertial mass is suspended. Said swinging motion can be generated by the influence of the oscillations in the rotor’s angular speed. The centripetal force acting on the inertial mass 13 produces a reactive centrifugal force having a component acting tangent to the motion in the direction towards an equilibrium position and thus provides a restoring force.

Accordingly, the inertial mass 13, thusly suspended from the carrier 7, forms a pendulum 17.

To achieve a broadband response, the pendulum 17 is tuned to a targeted order of the rotor’s angular speed. Therefore, when the rotor’s angular speed oscillates at that targeted order, the pendulum is tuned to the frequency of oscillations in the rotor’s angular speed. That is, the inertial mass 13 is influenced to oscillate at the same frequency as the rotor’s speed oscillates. Torsional vibration energy is therefore transferred from the rotor 3 into the oscillation of the inertial mass 13.

The tuning is effected by the geometry of a path to which the swinging motion of the inertial mass 13 is constrained. T o enable significant energy harvesting, it is desirable to increase the amplitude of the swinging motion and to sustain this motion without de tuning. Accordingly, the pendulum 17 is configured such that the inertial mass 13 is constrained to motion along a substantially tautochronic path 19 tuned to the targeted order.

A tautochronic path is an epicycloid path providing tautochronic (amplitude independent) tuning. The substantially tautochronic path 19 along which the inertial mass 13 can oscillate may be a tautochronic path and thus the oscillation frequency of the inertial mass 13 may be independent of nonlinear effects associated to the amplitude of its oscillations. Accordingly, the tuning of the pendulum 17 to the targeted order is maintained regardless of the rotor’s angular speed. The pendulum 17 does not detune as the amplitude of its oscillations increase. The oscillation frequency of the inertial mass 13 does not shift away from the frequency of the oscillations in the rotor’s angular speed as the amplitude of the oscillations increase, as may happen with increased rotor speed.

The substantially tautochronic path 19 along which the inertial mass 13 can oscillate may alternatively be a path which does not provide exact tautochronic tuning. For instance, the frequency with which the inertial mass 13 oscillates may have a weak dependence upon the amplitude of the oscillations. This may, in some cases, be due to manufacturing uncertainties, tolerances or ease of manufacture and/or assembly of the inertial mass 13 and its suspension point(s) from the carrier 7. The path 19 will in any case provide for a variable length pendulum 17, for example one in which an effective pendulum 17 length decreases with increasing displacement of the inertial mass 13 from its equilibrium position.

In some examples the substantially tautochronic path 19 may be comprised in a plane orthogonal to the rotor’s axis of rotation 5. As depicted in FIG 1 , said plane is the plane of the page. In some examples the effective pivot 15 is radially offset from the rotor’s axis of rotation 5. That is, the one or more points from which the inertial mass 13 is suspended are arranged such that the effective pivot 15 is radially offset from the rotor’s axis of rotation 5. In other examples the effective pivot 15 can coincide with the rotor’s axis of rotation 5 and means for dynamically adjusting the distance between the inertial mass 13 and the effective pivot 15, in order to yield the substantially tautochronic path 19, can be employed. For example, the inertial mass 13 may be suspended from the carrier 7 on one or more cables, wires, strings, or the like and bumpers arranged about which the one or more cables, wires, strings, or the like bend upon contact to shorten their effective length.

The inertial mass 13 comprises at least one permanent magnet 21. Accordingly, the motion of the inertial mass 13 relative to the at least one conductive coil 9 results in a voltage being induced in the at least one conductive coil 9.

The at least one permanent magnet 21 may be formed from any suitable hard ferromagnetic material. In some examples the inertial mass 13 consists of the at least one permanent magnet 21. In other examples the inertial mass 13 comprises any suitable soft ferromagnetic material by means of which the volume of the magnetic field produced by the at least one permanent magnet 21 may be increased. In still other examples, the inertial mass 13 can comprise so-called non-magnetic materials (such as paramagnetic, diamagnetic, and antiferromagnetic materials) by means of which the mass can be set as desired without an appreciable effect on the magnetic field produced. The inertial mass 13 may comprise both soft ferromagnetic materials and non-magnetic materials.

In some examples the carrier 7 is formed of a material or materials having non ferromagnetic properties, such as aluminium, so that it does not attract the at least one permanent magnet 21 , affecting the system dynamics.

As described in the foregoing and as depicted in FIG 1, the vibration energy harvesting device 1 comprises one pendulum 17 tuned to one targeted order; however, in some examples the vibration energy harvesting device 1 comprises one or more further pendulums tuned respectively to one or more further targeted orders of oscillations in the rotor’s angular speed. In some such examples, these further pendulums may be provided by suspending further inertial masses, comprising permanent magnets, from the carrier 7 such that they oscillate respectively along substantially tautochronic paths tuned to the further targeted orders and move relative to conductive coils supported by the carrier 7 so as to induce a voltage in these coils. For the avoidance of doubt, the geometry of these substantially tautochronic paths differ from one another and from the substantially tautochronic path 19 as a result of their tuning to different orders. The vibration energy harvesting device 1 of such examples can harvest energy from different harmonics of the torsional vibrations to which the rotor 3 is subjected.

Although, depicted in the FIGS as being mounted to just a portion of the rotor’s circumference, it is to be appreciated that the carrier 7 can completely encircle the rotor 3. Where one or more further pendulums tuned respectively to one or more further targeted orders of oscillations in the rotor’s angular speed are suspended from the carrier 7, these may be arranged at different angular positions around the rotor 3 to mechanically balance the load. It may be advantageous for the carrier 7 can completely encircle the rotor 3 for ease of facilitating this.

FIG 2 shows a lumped parameter model of an example of the pendulum 17. The rotor’s axis of rotation 5 is labelled. The effective pivot 15 of the pendulum 17 is in a fixed positional relationship with the rotor 3 and rotates about this axis 5. Movement of the inertial mass 13 about the effective pivot 15 follows the substantially tautochronic path 19. The displacement of the inertial mass 13 along the substantially tautochronic path 19 from the vertex 23 of the substantially tautochronic path 19 is denoted by s. The distance from the rotor’s axis of rotation 5 to the vertex 23 of the substantially tautochronic path 19 is denoted by c, its angular position is denoted by a, and 6 _t represents the angle between the inertial mass 13, effective pivot 15 and vertex 23 (the tangent angle to an epicycloid path).

Electromagnetic coupling between the mechanical pendulum 17 and the conductive coil 9 produces a mechanical force acting on the pendulum 17 as an electrical damping effect on the pendulum motion. The force is given by:

Felec — ^C elec S ~ F)1 where c _eiec denotes the electrical damping coefficient, Q denotes the electromagnetic coupling factor (the coupling between the mechanical and electrical parts of the vibration energy harvesting device 1) and I is the electrical current in the conductive coil 9.

To calculate the dynamic response of the pendulum 17, the following equation of motion of can be used: where c _mech is the mechanical damping of the pendulum 17, m is the inertial mass 13 of the pendulum 17, and g is the acceleration due to gravity. X(s) is provided by the following function:

X(s) = c ² — n ² s ² where n is the targeted order to which the pendulum 17 is tuned.

The above equation of motion assumes that the inertial mass 13 is sufficiently close to the rotor’s axis of rotation 5 that gravitational acceleration is significant compared to the centripetal acceleration (at least at low angular speeds, a). That is, gravitational acceleration is not negligible. It is to be appreciated however that in some examples of the present disclosure, the inertial mass 13 may be sufficiently far from the rotor’s axis of rotation 5 that acceleration due to gravity has a negligible effect relative to the centripetal acceleration acting on the inertial mass 13, in which case the gravitational acceleration term, g sin(a + 9 _t ) can be omitted from the equation of motion when calculating the dynamic response of the pendulum 17.

The voltage e induced in the conductive coil 9 depends on the dynamic response of the pendulum 17 and, by Faraday’s law, is given by: e = Qs The total power delivered to the electrical part of the vibration energy harvesting device 1 is therefore: and the usable power for any electrical loads connected to the conductive coil 9 is given by: where R _coU is the internal resistance in the conductive coil 9 and ff _ioad is the resistance of any electrical load coupled thereto.

The parameters of the pendulum 17 may be optimised to provide a dynamic response which yields a desired usable power.

In some examples, if the motion of the inertial mass 13 has little effect on the motion of the rotor 3, the oscillations in the rotor’s angular speed will remain for longer and the delivery of power to the electrical part of the vibration energy harvesting device 1 may be sustained for longer. In such examples, the vibration energy harvesting device 1 does not function as a vibration absorber or at least not effectively. One way of achieving this is to use a small inertial mass 13. In some examples, the motion of the inertial mass 13 has a negligible effect on the motion of the rotor 3 altogether. A sufficiently small mass for achieving this may satisfy the following condition: where I _d is the rotor’s mass moment of inertia, W is the rotor’s mean angular speed, N is the number of pendulums and c _tot is the total damping experienced by the pendulum 17 (mechanical and electrical).

FIG 3A schematically depicts an example vibration energy harvesting device 1 with the pendulum 17 in its equilibrium position and FIG 3B depicts the same example with the pendulum 17 displaced from its equilibrium position. For ease of visual inspection, FIG 3C depicts the same example absent the inertial mass 13 and FIG 3D depicts the inertial mass 13 absent from FIG 3C.

In the depicted example, the opposing magnetic poles 37, 39 of the at least one permanent magnet 21 are coplanar. At least while the pendulum 17 is in its equilibrium position, the opposing magnetic poles 37, 39 of the at least one permanent magnet 21 lie in a plane which is substantially orthogonal to the axis 11 around which the conductive coil 9 is wound.

The opposing magnetic poles 37, 39 may be exposed on the surface of the inertial mass 13 most proximate to and/or facing the conductive coil 9.

In some examples the opposing magnetic poles 37, 39 may be provided by a pair of permanent magnets 21. These may be attached to the inertial mass 13 in order to magnetise it.

In the plane orthogonal to the rotor’s axis of rotation 5, within which the inertial mass 13 moves, the width of the conductive coil 9 is such that the movement of the inertial mass 13 causes the magnetic flux enclosed by the conductive coil 9 to change. For example, the conductive coil 9 is not so wide that motion of the inertial mass 13 under the influence of oscillations in the rotor’s angular speed remains within the projected area of the conductive coil 9. In some examples, the width of the conductive coil 9 is less than the combined width of the opposing magnetic poles 37, 39 and any separation between them, thus ensuring that any motion in the plane orthogonal to the rotor’s axis of rotation 5 causes a change in the magnetic flux enclosed by the conductive coil 9. In some examples, the width of the conductive coil 9 is significantly smaller. The width of the conductive coil 9 may be selected to maximise the rate of change of magnetic flux enclosed by the conductive coil 9.

The inertial mass 13 can be suspended on one or more rollers 31 , 3T running on one or more curved tracks 33, 33' in the inertial mass 13 and/or one or more curved tracks 35, 35' in the carrier 7. The geometry of the one or more curved tracks 33, 33', 35, 35' are such as to constrain relative motion between the inertial mass 13 and the carrier 7 to motion along the substantially tautochronic path 19.

The one or more rollers 31 are rotatable about axes oriented parallel to the rotor’s axis of rotation 5.

In some examples these axes are not fixed in place and both the inertial mass 13 and the carrier 7 may move relative to these axes.

In other examples these axes may be fixed in place to the carrier 7. The one or more curved tracks 33, 33' in the inertial mass 13 may be the only tracks on which the one or more rollers 31 , 31 ' run. That is, there may be no tracks 35, 35' in the carrier 7. In still other examples these axes may be fixed in place to the inertial mass 13. The one or more curved tracks 35, 35' in the carrier 7 may be the only tracks on which the one or more rollers 31 , 3T run. That is, there may be no tracks 33, 33' in the inertial mass 13.

The one or more curved tracks 33, 33' in the inertial mass 13 may be cut through the inertial mass 13 so that the one or more rollers 31 , 3T can extend through the inertial mass 13 and protrude on either side. The carrier 7 may be formed so as to support the one or more rollers 31, 3T on either side of the inertial mass 13, whether by providing fixing points for the one or more rollers 31, 31 ' on either side of the inertial mass 13 or by receiving the one or more rollers 31 , 3T in one or more curved tracks 35, 35' on either side of the inertial mass 13.

In the depicted example, the one or more curved tracks 33, 33' in the inertial mass 13 are curved in an opposite direction to the one or more curved tracks 35, 35' in the carrier 7. In some examples the one or more curved tracks 33, 33' in the inertial mass 13 appear convex from the perspective of the axis of rotation 5 whereas the one or more curved tracks 35, 35' in the carrier 7 appear concave from the perspective of the axis of rotation 5. The geometry of the one or more curved tracks 33, 33' may be mirrored with respect to the geometry of the one or more curved tracks 35, 35'. In the depicted example the inertial mass 13 is suspended on twin rollers 31 , 31' running on twin sets of curved tracks 33, 33' and 35, 35', displaced from one another in a direction perpendicular to an axis 11 around which the conductive coil 9 is wound. The thusly, formed pendulum 17 is therefore functionally bifilar.

The suspension of the inertial mass 13 on twin rollers 31 , 3T running on twin sets of curved tracks 33, 33' and 35, 35', enables the plane in which the opposing magnetic poles 37, 39 of the at least one permanent magnet 21 lie to remain substantially orthogonal to the axis 11 around which the conductive coil 9 is wound while the inertial mass 13 oscillates along the substantially tautochronic path 19. That is, the magnetic poles 37, 39 are not rotated with respect to the conductive coil 9.

It will be appreciated that the same effect can be achieved in other examples in which the twin rollers 31, 31 ' may run on twinned tracks 33, 33' in the inertial mass 13 while having a fixed position in respect of the carrier 7 or in which the twin rollers 31 , 31 ' may run on twinned tracks 35, 35' in the carrier 7 while having a fixed position in respect of the inertial mass 13.

Although in the foregoing, the carrier 7 has been described as supporting the at least one conductive coil 9 and the pendulum 17 has been described as being formed from suspending the at least one permanent magnet 21 , as comprised in the inertial mass 13, from the carrier 7, it is to be appreciated that the at least one conductive coil 9 and the at least one permanent magnet 21 could switch places as is depicted in FIG 4 and FIGS 5A-D.

FIG 4 schematically depicts another example of a vibration energy harvesting device 1 for converting energy of targeted order oscillations in a rotor’s angular speed into electrical energy.

In this example the vibration energy harvesting device 1 comprises a carrier 7 supporting at least one permanent magnet 21 and configured to be mounted to, and thereby rotate at a same angular speed as, the rotor 3. The carrier 7 can be as described in relation to FIG 1 except that it supports the at least one permanent magnet 21 rather than the at least one conductive coil 9. In this example the vibration energy harvesting device 1 comprises a pendulum 17 formed from an inertial mass 13 suspended from the carrier 7 such that the inertial mass 13 can oscillate along a substantially tautochronic path 19 which is tuned to the targeted order. The difference between the pendulum 17 described in FIG 1 and 2 and the pendulum 17 of the example depicted in FIG 4 is that the inertial mass 13 comprises the at least one conductive coil 9 rather than the at least one permanent magnet 21.

The motion of the at least one conductive coil 9, relative to the at least one permanent magnet 21, induces a voltage in the at least one conductive coil 9.

In some examples, and as depicted in FIG 4, the vibration energy harvesting device 1 can be configured to be mounted to the rotor 3 such that an effective pivot 15 of the pendulum 17 is radially offset from the rotor’s axis of rotation 5.

In some examples, and as depicted in FIG 4, the vibration energy harvesting device 1 can be configured to be mounted to the rotor 3 such that an axis 11 around which at least one conductive coil 9 is wound is perpendicular to the rotor’s axis of rotation 5 when the pendulum 17 is in its equilibrium position.

As with the example vibration energy harvesting device 1 depicted in FIG 1, examples of the vibration energy harvesting device 1 in which: the at least one conductive coil 9 is comprised in the inertial mass 13 of the pendulum 17; and the at least one permanent magnet 21 is supported by the carrier 7 so that it rotates at the same angular speed as the rotor 3, can comprise one or more further pendulums tuned respectively to one or more further targeted order oscillations in the rotor’s angular speed and suspended from the carrier 7. In some such examples, these further pendulums may be provided by suspending further inertial masses, comprising conductive coils, from the carrier 7 such that they oscillate respectively along substantially tautochronic paths tuned to the further targeted orders and move relative to permanent magnets supported by the carrier 7 so as to induce a voltage in these coils.

In some examples the carrier 7 may be as described in relation to FIGS 3A-C except that it supports the at least one permanent magnet 21 rather than the at least one conductive coil 9 and the pendulum 17 may be as described in relation to FIGS 3A, B and D except that the inertial mass 13 comprises the at least one conductive coil 9 rather than the at least one permanent magnet 21. An example of the resultant vibration energy harvesting device 1 is depicted in FIG 5A-D. FIG 5A depicts the pendulum 17 in its equilibrium position, FIG 5B depicts the pendulum 17 displaced from its equilibrium position, and FIGS 5C and 5D respectively depict the carrier 7 and inertial mass 13 separately.

The inertial mass 13, comprising the at least one conductive coil 9, can be suspended on one or more rollers 31, 3T running on a curved track 33, 33' in the inertial mass 13 and/or a curved track 35, 35' in the carrier 7.

The geometry of the one or more curved tracks 33, 33', 35, 35' can be such as to constrain relative motion between the inertial mass 13, comprising the at least one conductive coil 9, and the carrier 7, supporting the at least one permanent magnet 21, to motion along the substantially tautochronic path 19.

The curved track 33, 33' in the inertial mass 13 can be curved in an opposite direction to the curved track 35, 35' in the carrier 7.

The inertial mass 13, comprising the at least one conductive coil 9, can be suspended on twin rollers 31, 3T running on twin sets of curved tracks 33, 33' and 35, 35', displaced from one another in a direction perpendicular to an axis 11 around which the at least one conductive coil 9 is wound.

Magnetic poles 37, 39 of the at least one permanent magnet 21, supported by the carrier 7, can be coplanarand lie in a plane which is substantially orthogonal to an axis 11 around which the at least one conductive coil 9 is wound.

If the inertial mass 13, comprising the at least one conductive coil 9, is suspended on the above-mentioned twin rollers 31 , 3T running on twin sets of curved tracks 33, 33' and 35, 35', the axis 11 around which the at least one conductive coil 9 is wound is not rotated relative to the plane in which the magnetic poles 37, 39 lie.

FIG 6 schematically depicts a sensing system 41 comprising one or more sensors 43 powered by electrical energy obtained by the vibration energy harvesting device 1. The sensing system 41 comprises the vibration energy harvesting device 1 along with circuitry 47 configured to operate the one or more sensors 43 using the electrical energy from the vibration energy harvesting device 1.

In some examples, such as the one depicted, but not necessarily all examples, the sensing system 41 also comprises one or more wireless transceivers 45. The one or more wireless transceivers 45 are configured to transmit sensor data and/or data produced by processing the sensor data. The one or more wireless transceivers 45 enable a wireless connection between the sensing system 41 and a remote device (which may, in some examples, be part of the same machine in which the sensing system 41 is installed). The wireless connection could be via short-range radio communications such as Wi-Fi or Bluetooth, for example, or over long-range cellular radio links or any other suitable type connection. The circuitry 47 is also configured to operate the one or more wireless transceivers 45 using the electrical energy from the vibration energy harvesting device 1.

In some examples the circuitry 47 comprises means 49 allowing for the transmission of power and electrical signals from a rotating to a stationary structure. The means 49 may be, for example, a slip ring or rotary transformer or any other suitable means.

In some examples the circuitry 47 comprises an alternating to direct current convertor 51 such as a rectifier.

In some examples the circuitry 47 comprises an electrical energy storage means 53 configured to be charged by the electrical energy from the vibration energy harvesting device 1 and to release stored energy to enable operation of the one or more sensors 43 and, in some examples, the one or more wireless transceivers 45. The electrical energy storage means 53 may be, for example, a capacitor, supercapacitor, rechargeable battery, or any other suitable means.

In some examples the circuitry 47 comprises a controller 55. The controller 55 is configured to read the signal output from the one or more sensors 43 to obtain measurement data. Optionally, the controller 55 may control what data is transmitted from the one or more wireless transceivers 45. The controller 55 can be further configured to manage the charging and discharging of the electrical energy storage means 53. For example, the controller 55 may measure when the electrical energy storage means 53 has charged to an upper threshold and, in response, obtain and, optionally, transmit measurement data and may measure when the electrical energy storage means 53 has discharged to a lower threshold and, in response, suspend the obtaining of measurement data so that the electrical energy storage means 53 is able to recharge. This cycle can be repeated with data transmission able to occur whenever the electrical energy storage means 53 is sufficiently charged. In some examples the controller 55 is configured to provide periodic transmission of data.

Implementation of the controller 55 may in hardware alone, have certain aspects in software including firmware alone or can be a combination of hardware and software (including firmware).

The controller 55 may be implemented using instructions that enable hardware functionality, for example, by using executable instructions (code) of one or more computer programs, stored in and loaded from memory, in at least one general- purpose or special-purpose processor. The instructions provide the logic and routines that enable the sensing system 41 to perform the gathering and, optionally, transmission of measurement data.

Said processor is configured to read from and write to memory. By reading the memory, the processor is able to load and execute a computer program stored in the memory. The processor can be implemented as a single component/circuitry or as one or more separate components/circuitry some or all of which may be integrated/removable. The memory can be implemented as a single component/circuitry or as one or more separate components/circuitry some or all of which may be integrated/removable and/or may provide permanent/semi-permanent/ dynamic/cached storage.

The functions of the controller 55 may be split between different hardware, each comprising a processor and memory storing a computer program which, when executed by the processor, performs respective functions. For example, reading the signal output from the one or more sensors 43 and, optionally, controlling transmission from the one or more wireless transceivers 45 can be performed by a microcontroller (MCU) or other computer, while managing the charging and discharging of the electrical energy storage means 53 may be performed by a power management unit (PMU). The PMU may coordinate when measurement data is gathered and transmitted and when the electrical energy storage means 53 is recharged. The PMU may communicate with the MCU via a bidirectional channel.

References to controller, computer, processor, etc. should be understood to encompass not only computers having different architectures such as single /multi processor architectures and sequential (Von Neumann)/parallel architectures but also specialized circuits such as field-programmable gate arrays (FPGA), application specific circuits (ASIC), signal processing devices and other processing circuitry. References to computer program, instructions, code, etc. should be understood to encompass software for a programmable processor or firmware such as, for example, the programmable content of a hardware device whether instructions for a processor, or configuration settings for a fixed-function device, gate array or programmable logic device etc.

Although the means 49 allowing for the transmission of power and electrical signals from a rotating to a stationary structure is depicted in FIG 6 to precede the other components 51 , 53, 55 of the circuitry 47, it is to be appreciated that any of these may be mounted to rotate with the rotor 3, either as part of or mounted to the vibration energy harvesting device 1 or as separately mounted to the rotor 3. In such examples the means 49 allowing for the transmission of power and electrical signals from a rotating to a stationary structure is connected between the components which rotate with the rotor 3 and those which do not.

In some examples, the one or more sensors 43 too could be mounted to rotate with the rotor 3 in which case the means 49 allowing for the transmission of power and electrical signals from a rotating to a stationary structure may be omitted from the circuitry 47. In such examples, the vibration energy harvesting device 1 can comprise: the one or more sensors 43; optionally, the one or more wireless transceivers 45; and the circuitry 47 configured to operate the one or more sensors 43 and, optionally, the one or more wireless transceivers 45 using the electrical energy induced in the conductive coil 9. FIG 7 schematically depicts a machine 63 comprising a rotor 3 and the vibration energy harvesting device 1 mounted to the rotor 3.

The one or more sensors 43, whether as part of the vibration energy harvesting device 1 or as comprised in the sensing system 41 described in relation to FIG 6 above, can be comprised within the machine 63.

In some examples, the one or more sensors 43 comprised within the machine 63 are inaccessible. The one or more sensors 43 are inaccessible to humans while within the machine 63. They are inaccessible without at least partial disassembly of the machine 63. By inaccessible, it is meant that a human would be either unable to view, with a naked eye, the sensor 43 without at least partial disassembly of the machine 63 or unable to effect substantial digital (in the sense of fingers) manipulation of the sensor 43 or without at least partial disassembly of the machine 63. Substantial digital manipulation may include, for example, the level of digital manipulation required in order to replace a battery, if the one or more sensors 43 were to be powered by a battery. Therefore, the one or more sensors 43 may be inaccessible in so far as would withstand attempts to change a battery, if they were to be powered by a battery, without at least partial disassembly of the machine 63. For the avoidance of doubt, at least partial disassembly of the machine 63 includes removal of the one or more sensors 43 from the machine 63.

In some examples the machine 63 comprises a housing 65 within which the one or more sensors 43 are disposed. The housing 65 may enclose the one or more sensors 43 thereby making the one or more sensors 43 inaccessible without removal of the housing 65 or parts of the housing 65. If there are apertures in the housing 65, other machine parts 69 disposed within the housing 65 may obstruct access to the one or more sensors 43 from these apertures. In obstructing access, these other machine parts 69 may be interposed between the apertures and the location of the one or more sensors 43.

In other examples the machine 63 may comprise no housing. The one or more sensors 43 may nevertheless be rendered inaccessible by the positioning of other machine parts 69. These other machine parts 69 may obstruct access to the one or more sensors 43 from positions external to the machine 63. In obstructing access, these other machine parts 69 may be interposed between positions external to the machine 63 and the location of the one or more sensors 43.

In some examples the sensing system 41 as a whole, whether comprising the one or more wireless transceivers 45 or not, can be comprised within the machine 63.

In some examples, the sensing system 41, or components thereof, comprised within the machine 63 is/are inaccessible. The sensing system 41 , or components thereof, is/are inaccessible to humans while within the machine 63. They are inaccessible without at least partial disassembly of the machine 63. By inaccessible, it is meant that a human would be either unable to view, with a naked eye, the sensing system 41, or components thereof, without at least partial disassembly of the machine 63 or unable to effect substantial digital (in the sense of fingers) manipulation of the sensing system 41, or components thereof, or without at least partial disassembly of the machine 63. Substantial digital manipulation may include, for example, the level of digital manipulation required in order to replace a battery, if the sensing system 41, or components thereof, were to be powered by a battery. Therefore, the sensing system 41 , or components thereof, may be inaccessible in so far as would withstand attempts to change a battery, if they were to be powered by a battery, without at least partial disassembly of the machine 63. For the avoidance of doubt, at least partial disassembly of the machine 63 includes removal of the sensing system 41, or components thereof, from the machine 63.

In some examples the machine 63 comprises a housing 65 within which the sensing system 41, or components thereof, are disposed. The housing 65 may enclose the sensing system 41, or components thereof, thereby making the sensing system 41, or components thereof, inaccessible without removal of the housing 65 or parts of the housing 65. If there are apertures in the housing 65, other machine parts 69 disposed within the housing 65 may obstruct access to the sensing system 41, or components thereof, from these apertures. In obstructing access, these other machine parts 69 may be interposed between the apertures and the location of the sensing system 41, or components thereof.

In other examples the machine 63 may comprise no housing. The sensing system 41, or components thereof, may nevertheless be rendered inaccessible by the positioning of other machine parts 69. These other machine parts 69 may obstruct access to the sensing system 41, or components thereof, from positions external to the machine 63. In obstructing access, these other machine parts 69 may be interposed between positions external to the machine 63 and the location of the sensing system 41, or components thereof.

It is to be understood that inaccessible may refer to physical inaccessibility and thus that the one or more wireless transceivers 45, as may be comprised in an inaccessible sensing system 41 , are still able to communicate with remote devices even though other machine parts 69 or housing 63 may be interposed between them. That is, the other machine parts 69 or housing 63 may not provide electromagnetic shielding.

In some examples the machine 63 comprises a torque source 67 (such as a combustion engine or electric motor) configured to drive rotation of the rotor 3. In other examples the torque source 67 may be replaced by a torque transmitter where the source of torque is distinct from the machine 63. The torsional vibrations to which the rotor 3 is subjected may be introduced by the torque source 67 or the torque transmitter.

Accordingly, it is advantageous to provide these inaccessible one or more sensors 43 or sensing system 41 as a whole with electrical energy harvested from the oscillations in the rotor’s angular speed using the vibration energy harvesting device 1 as this avoids the need for disassembly once the one or more sensors 43 or sensing system 41 as a whole have/has been installed in the machine 63, as may otherwise be required in order to maintain battery-powered sensors or systems. By configuring the vibration energy harvesting device 1 to support the sensing system 41 , such that the means 49 allowing for the transmission of power and electrical signals from a rotating to a stationary structure is unnecessary, by providing the one or more wireless transceivers 45, and by implementing the components of the sensing system 41 by ASICs or other integrated circuits (for example, the one or more sensors 43 may be implemented with microelectromechanical system technology) potentially cumbersome electrical wiring can be avoided. Accordingly, various embodiments hereinbefore described enable challenging monitoring tasks in difficult to reach areas within the machine 63 to be more easily accomplished, allowing parameters such as temperature, forcing, fluid properties etc. to be more easily measured. The machine 63 may be a vehicle including automotive vehicles of both passenger and industrial types, railed vehicles, watercrafts, aircrafts, and the like.

Consequently, there is provided a vehicle comprising the vibration energy harvesting device 1 , and optionally the rest of the sensing system 41 , wherein the vehicle comprises a driveshaft (the rotor 3), and wherein the vibration energy harvesting device 1 is configured to convert one or more targeted orders of the driveshaft’s speed oscillations into electrical energy. The vehicle may comprise a prime mover configured to drive rotation of the driveshaft, or in the case of certain railed vehicles, for example, it may not and may instead comprise means for transmitting externally generated torque to the driveshaft.

It is to be appreciated that the electrical energy obtained from the oscillations in the rotor’s angular speed by the vibration energy harvesting device 1 may be used to operate any electronic component instead of the one or more sensors 43. Said electronic component(s) may be comprised within the machine 63 and may be inaccessible in the manner described of the one or more sensors 43 in the foregoing. The circuitry 47 may be configured to operate said electronic component(s) using the electrical energy from the vibration energy harvesting device 1.

The term ‘comprise’ is used in this document with an inclusive not an exclusive meaning. That is any reference to X comprising Y indicates that X may comprise only one Y or may comprise more than one Y. If it is intended to use ‘comprise’ with an exclusive meaning then it will be made clear in the context by referring to “comprising only one” or by using “consisting”.

In this description, reference has been made to various examples. The description of features or functions in relation to an example indicates that those features or functions are present in that example. The use of the term ‘example’ or ‘for example’ or ‘can’ or ‘may’ in the text denotes, whether explicitly stated or not, that such features or functions are present in at least the described example, whether described as an example or not, and that they can be, but are not necessarily, present in some of or all other examples. Thus ‘example’, ‘for example’, ‘can’ or ‘may’ refers to a particular instance in a class of examples. A property of the instance can be a property of only that instance or a property of the class or a property of a sub-class of the class that includes some but not all of the instances in the class. It is therefore implicitly disclosed that a feature described with reference to one example but not with reference to another example, can where possible be used in that other example as part of a working combination but does not necessarily have to be used in that other example.

Although examples have been described in the preceding paragraphs with reference to various examples, it should be appreciated that modifications to the examples given can be made without departing from the scope of the claims.

Features described in the preceding description may be used in combinations other than the combinations explicitly described above.

Although functions have been described with reference to certain features, those functions may be performable by other features whether described or not.

Although features have been described with reference to certain examples, those features may also be present in other examples whether described or not.

The term ‘a’ or ‘the’ is used in this document with an inclusive not an exclusive meaning. That is any reference to X comprising a/the Y indicates that X may comprise only one Y or may comprise more than one Y unless the context clearly indicates the contrary. If it is intended to use ‘a’ or ‘the’ with an exclusive meaning then it will be made clear in the context. In some circumstances the use of ‘at least one’ or ‘one or more’ may be used to emphasis an inclusive meaning but the absence of these terms should not be taken to infer any exclusive meaning.

The presence of a feature (or combination of features) in a claim is a reference to that feature or (combination of features) itself and also to features that achieve substantially the same technical effect (equivalent features). The equivalent features include, for example, features that are variants and achieve substantially the same result in substantially the same way. The equivalent features include, for example, features that perform substantially the same function, in substantially the same way to achieve substantially the same result. In this description, reference has been made to various examples using adjectives or adjectival phrases to describe characteristics of the examples. Such a description of a characteristic in relation to an example indicates that the characteristic is present in some examples exactly as described and is present in other examples substantially as described.

Whilst endeavoring in the foregoing specification to draw attention to those features believed to be of importance it should be understood that the Applicant may seek protection via the claims in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not emphasis has been placed thereon.

I/we claim: