GB1564007A

GB1564007A - Machines

Info

Publication number: GB1564007A
Application number: GB3272676A
Authority: GB
Original assignee: Marconi Co Ltd
Current assignee: BAE Systems Electronics Ltd
Priority date: 1976-08-05
Filing date: 1976-08-05
Publication date: 1980-04-02
Also published as: DE2646497B2; DE2646497A1; DE2646497C3

Description

(54) IMPROVEMENTS IN OR RELATING TO MACHINES (71) We, THE MARCONI COMPANY LIMITED, a British Company, of Marconi House, New Street, Chelmsford, Essex, cM1 lPL, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to machines and more specifically to machines in which rotational motion is imparted to a body.

It is commonly required to impart rotational motion to a body about an axis which is controlled either to achieve a stabilisinig effect so that the direction of the axis of rotation tends to remain constant in the face of certain external influences or to achieve a controlled change in the direction of the axis. Such a requirement exists in the aerial field, for example, where the carrier of a scanning aerial is required to be rotated about a controlled axis.

It is an object of the present invention to provide an improved machine for imparting rotational motion to a body about a controlled axis.

According to this invention there is provided a machine wherein relative rotational motion is provided between two bodies, one of said two bodies having a surface which is, at least in part, at least approximately spherical, and the other of said two bodies having a plurality of electromagnetic means arranged around a circle to produce, when energised lines of force cutting said surface of said one body, said two bodies being arranged such that the at least approximately spherical surface of said one body may move radially with respect to said circle over said electromagnetic means of said other body, and including means for applying polyphase alternating electric current to energise said electromagnetic means to effect relative rotation between said two bodies about an axis passing through said circle and means for varying the phase of said alternating electric current applied to at least one of said electromagnetic means whereby said axis of rotation, together with said one body, is tilted.

Preferably each electro-magnetic means consists of an individual electro-magnetic coil mounted on a core.

Preferably said core is a '4U" shaped core the connecting portion of which extends radially from the axis of said circle, in which case preferably the surfaces of said coil and core assemblies which face the said surface of said one body lie at least approximately on the surface of an imaginary sphere which is concentric with the said surface of said one member.

Preferably again three electro-magnetic coils are provided around said circle, angularly spaced by 120 and each arranged to be fed with an appropriate one of the phases of a regular three phase supply.

Mechanical means may be provided supporting one of said two bodies from the other.

Preferably, however, a further plurality of electro-magnetic means are arranged around a second circle, concentric with said first mentioned circle, to produce, when energised, lines of force cutting said surface of said one body and a radial force in opposition to a radial force produced by said first mentioned plurality of electro-magnetic means and tending to produce relative lateral motion between said two bodies.

Preferably again each of said further electro-magnetic means comprises a coil and core assembly and preferably for each elec tro-magnetic coil around said first mentioned circle, a radially aligned electromagnetic coil is provided in said second circle.

In the case described immediately above it will be found possible in many cases to support said one body from the other, or vice versa, by electro-magnetic levitation effects alone.

Said one body may comprise magnetic material. In some embodiments of the invention, however, said one body comprises non-magnetic material, such as aluminium or copper, into which eddy currents are induced due to said lines of force cutting said surface of said one body. It is, of course, necessary for there to be a repulsive effect between said two bodies if the effects of magnetic levitation are to be relied upon in supprting said one body from the other, or vice versa.

In another embodiment of the invention said one member comprises a spherical coil, wound in squirrel cage fashion.

Means may be provided for varying the voltage and phase of the supply to at least one of said electro-magnetic means.

Either said one member or said other member may be fixed relative to a reference surface, in which case said other member or said one member may carry apparatus, such as an aerial system, which is required to be rotated about an axis relative to said reference surface.

The invention is illustrated in and further described with reference to the drawings accompanying the Provisional Specification in which, Figure 1 is a plan view of the stator of one machine in accordance with the present invention, Figure 2 is a part cut away side elevation of one machine utilising the stator of Figure 1, Figure 3 illustrates a preferred stator, Figure 4 is a section in elevation of another machine in accordance with the present invention, and Figure 5 is a plan view of the core of the stator used in the machine of Figure 4 in an unwound state.

Like references are used for like parts throughout.

Referring to Figures 1 and 2, the stator consists of an arrangement of three "U" shaped cores, 1, 2, 3, each carrying a coil winding 4, 5 and 6 respectively. The cores 1, 2 and 3 extend radially from a vertical axis 7 and are angularly spaced one from another by 1200. Each core 1, 2 or 3 and its respective coil 4, 5 or 6 are precisely similar and, as best seen from Figure 2, have upper surfaces which lie approximately on the surface of an imaginary sphere 8 (shown dotted) in Figure 2.

The rotor consists of a spherical dish 9 of aluminium. The sphericaly under-surface of the aluminium dish 9 is concentric with the imaginary sphere 8. The aluminium dish 9 is suspended by a plurality of radially disposed suspension rods, of which one, referenced 10, is shown in Figure 1. The suspension rods such as 1-0 are attached to a fixed point (not shown) above the dish 9 and lying on the axis 7. The suspension rods such as 10 are attached to the aforementioned fixed point above the dish 9 in such manner (e.g.

by the use of a rotatable collar) so that the assembly of the dish 9 with its suspension rods such as 10 may rotate about the axis 7, as it were in "maypole" fashion. The lengths of the suspension rods such as 10 are arranged to provide a small air gap 11 between the imaginary spherical surface 8 and the aluminium dish 9.

The power supply to the coils 4, 5 and 6 is three phase. The first phase is connected to coil 5 (as represented at 12), the second phase is connected to coil 6 (as represented by 13), and the third phase is connected to coil 4 (as represented at 14). The arrows 15, 16 and 17 associated with the phases 12, 13 and 14 respectively represent that each of the three phases are relatively adjustable.

In operation, with the three phase supply connected and with each of the phases of similar voltage, a magnetic field is created which rotates. Due to eddy current effects in the matrial af the dish 9 a repulsive force is created which acts towards the geometric centre of the sphere 8. This repulsive force couples the aluminium dish to the rotating magnetic field and the dish rotates about the vertical axis 7. If now the phase applied to one of the coils 4, 5 or 6 is varied, the dish 9 continues to rotate, but the axis of rotation departs from the vertical axis 7. In other words, the dish and its rotational axis tilts.

In the embodiment described above, levitation of the dish 9 tends to occur. However, levitation is restrained by the suspension of the dish 9. With a stator arrangement as shown in Figure 1, it is not possible to dispense with the suspension of the dish 9 and to rely upon the leviation effect achieved to provide the required working clearance represented by the air-gap 11, since the position of the axis of rotation of the dish 9, irrespective of the adjustment of the voltages of the three phases, is basically unstable and without the constraint imposed by the suspension the dish 9 would tend to move out of the field.

Referring to Figure 3, in this example stability of the position of the axis of rotation of a dish such as the dish 9 of Figure 2 is achieved without the necessity of the constrain imposed by a mechanical suspension.

This is achieved by providing not just one ring of coils on the stator, as shown in Figure 1, but an inner and an outer ring of coils. The individual coils in the outer ring have been referenced 4, 5 and 6 in conformity with Figure 1 and each is mounted on a "U" shaped core, again referenced 1, 2 and 3 in conformity with Figure 1. The inner ring of coils consists of three coils 19, 20 and 21, each mounted on a "U" shaped core 22, 23 and 24 respectively. It will be seen that in this example, inner coil 20 is radially aligned with outer coil 5, inner coil 21 is radially aligned with outer coil 6 and inner coil 9 is radially aligned with outer coil 4. The upper surfaces of all of the coil and core assemblies lie approximately on the surface of an imaginary sphere equivalent to 8 in Figure 2.

Again coils 4, 5 and 6 are supplied each with one phase of a three phase supply as represented at 14, 15 and 13 respectively.

Each of the inner coils 19, 20 and 21 are also supplied, as represented at 25, 26 and 27, with one of the phases of the same three phase power supply, but, not the same phase as is applied to the outer coil 4, 5 or 6 with which it is radially aligned. The object is to ensure that between radially aligned inner and outer coils, there is a phase lead or lag.

ln this present example, if one conventionally considers the three phases of the three phase supply to be red phase, blue phase and yellow phase, then red phase is applied to outer coil 5 and inned coil 21, blue phase is applied to outer coil 6 and inner coil 19, whilst yellow phase is applied to outer coil 4 and inner coil 20.

With such an arrangement the aluminium dish 9 will be found to rotate about an axis which is stable although fully supported by the levitation effect of the magnetic field.

The stability of the axis of rotation is due to the fact that with the single ring of coils shown in Figure 1, a travelling field is produced which acts radially outwards. The eddy currents induced in the aluminium dish 9 lag the current in the coils and the currents flowing in the dish furthest from the axis have an increased lag due to cur tents nearer to the axis. Providing the inner ring of coils 19, 20 and 21 and feeding these with a lagging current compared with the outer ring of coils acts to provide an inwardly directed force which opposes the aforementioned outwardly acting force.

In fact, not only is the rotational axis stabilised, but, if the position of the aluminium dish is disturbed a restoring force acts to re-establish the axis of rotation. The extra repulsive forces also enhance levitation effect, whilst at the same time, compared with the arrangement utilised the stator of Figure 1, rotation does not appear to be impaired.

By altering the phase of one of the outer coils 4, 5 or 6, the radial force exerted by the stator is modified and the aluminium dish 9 together with its rotational axis will tilt and then rotate with stability.

With the embodiments so far described the stator comprises the magnetic field producing means whilst the rotor is the member in which eddy currents are induced. It is, of course, possible to reverse the roles and provide the coil assembly as the rotor.

Furthermore, the rotor has been described as an aluminium dish, in other words, of a material not conventionally regarded as magnetic. Other such materials may be used, for example copper. Furthermore, the rotor itself in an example otherwise as hitherto described may itself be magnetic, for example, it may be constituted by a spherical coil and one such embodiment will now be described with reference to Figures 4 and 5.

Referring to Figure 4, the stator consists of a core 28, which is shown in plan view in Figure 5 (in an unwound state) having an outer ring of windings 29 like windings 4, 5 ad 6 of Figure 3 and an inner ring of windings 30 like windings 19, 20 and 21 of Figure 3. Again the windings in the outer ring of windings 29 are supplied with progressively different phases, as are the windings of the inner ring of windings, with again a lag between radially aligned inner and outer windings. The rotor consists of a part spherical core 31 of magnetic material, which in this example, is suspended by suspension members such as 32 from a variable axis shaft 33 carried by a spherical bearing 34. Carried on the rotor core 31 is a squrrel cage rotor winding 33.

Referring more particularly to Figure 5, the core consists essentially of concentric wound strips. Slots for the windings are shown at 35.

WHAT WE CLAIM IS:- 1. A machine wherein relative rotational motion is provided between two bodies, one of said two bodies having a surface which is, at least in part, at least approximately spherical, and the other of said two bodies having a plurality of electromagnetic means arranged around a circle to produce, when energised, lines of force cutting said surface of said one body, said two bodies being arranged such that the at least approximately spherical surface of said one body may move radially with respect to said circle over said electromagnetic means of said other body, and including means for applying polyphase alternating electric current to energise said electromagnetic means to effect relative rotation between said two bodies about an axis passing through said circle and means for varying the phase of said alternating electric current applied to at least one of said electro-magnetic means whereby said axis of rotation, together with said one body, is tilted.

2. A machine as claimed in claim 1 and wherein each electro-magnetic means consists of an individual electro-magnetic coil mounted on a core.

3. A machine as claimed in claim 2 and wherein said core is a "U" shaped core the connecting portion of which extends radially from the axis of said circle.

4. A machine as claimed in claim 3 and wherein the surfaces of said coil and core assemblies which face the said surface of said one body lie at least approximately on the surface of an imaginary sphere which is

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. the surface of an imaginary sphere equivalent to 8 in Figure 2. Again coils 4, 5 and 6 are supplied each with one phase of a three phase supply as represented at 14, 15 and 13 respectively. Each of the inner coils 19, 20 and 21 are also supplied, as represented at 25, 26 and 27, with one of the phases of the same three phase power supply, but, not the same phase as is applied to the outer coil 4, 5 or 6 with which it is radially aligned. The object is to ensure that between radially aligned inner and outer coils, there is a phase lead or lag. ln this present example, if one conventionally considers the three phases of the three phase supply to be red phase, blue phase and yellow phase, then red phase is applied to outer coil 5 and inned coil 21, blue phase is applied to outer coil 6 and inner coil 19, whilst yellow phase is applied to outer coil 4 and inner coil 20. With such an arrangement the aluminium dish 9 will be found to rotate about an axis which is stable although fully supported by the levitation effect of the magnetic field. The stability of the axis of rotation is due to the fact that with the single ring of coils shown in Figure 1, a travelling field is produced which acts radially outwards. The eddy currents induced in the aluminium dish 9 lag the current in the coils and the currents flowing in the dish furthest from the axis have an increased lag due to cur tents nearer to the axis. Providing the inner ring of coils 19, 20 and 21 and feeding these with a lagging current compared with the outer ring of coils acts to provide an inwardly directed force which opposes the aforementioned outwardly acting force. In fact, not only is the rotational axis stabilised, but, if the position of the aluminium dish is disturbed a restoring force acts to re-establish the axis of rotation. The extra repulsive forces also enhance levitation effect, whilst at the same time, compared with the arrangement utilised the stator of Figure 1, rotation does not appear to be impaired. By altering the phase of one of the outer coils 4, 5 or 6, the radial force exerted by the stator is modified and the aluminium dish 9 together with its rotational axis will tilt and then rotate with stability. With the embodiments so far described the stator comprises the magnetic field producing means whilst the rotor is the member in which eddy currents are induced. It is, of course, possible to reverse the roles and provide the coil assembly as the rotor. Furthermore, the rotor has been described as an aluminium dish, in other words, of a material not conventionally regarded as magnetic. Other such materials may be used, for example copper. Furthermore, the rotor itself in an example otherwise as hitherto described may itself be magnetic, for example, it may be constituted by a spherical coil and one such embodiment will now be described with reference to Figures 4 and 5. Referring to Figure 4, the stator consists of a core 28, which is shown in plan view in Figure 5 (in an unwound state) having an outer ring of windings 29 like windings 4, 5 ad 6 of Figure 3 and an inner ring of windings 30 like windings 19, 20 and 21 of Figure 3. Again the windings in the outer ring of windings 29 are supplied with progressively different phases, as are the windings of the inner ring of windings, with again a lag between radially aligned inner and outer windings. The rotor consists of a part spherical core 31 of magnetic material, which in this example, is suspended by suspension members such as 32 from a variable axis shaft 33 carried by a spherical bearing 34. Carried on the rotor core 31 is a squrrel cage rotor winding 33. Referring more particularly to Figure 5, the core consists essentially of concentric wound strips. Slots for the windings are shown at 35. WHAT WE CLAIM IS:-

1. A machine wherein relative rotational motion is provided between two bodies, one of said two bodies having a surface which is, at least in part, at least approximately spherical, and the other of said two bodies having a plurality of electromagnetic means arranged around a circle to produce, when energised, lines of force cutting said surface of said one body, said two bodies being arranged such that the at least approximately spherical surface of said one body may move radially with respect to said circle over said electromagnetic means of said other body, and including means for applying polyphase alternating electric current to energise said electromagnetic means to effect relative rotation between said two bodies about an axis passing through said circle and means for varying the phase of said alternating electric current applied to at least one of said electro-magnetic means whereby said axis of rotation, together with said one body, is tilted.

concentric with the said surface of said one member.

5. A machine as claimed in any of the above claims and wherein three electromagnetic coils are provided around said circle, angular spaced by 1200 and each arranged to be fed with an appropriate one of the phases of a regular three phase supply.

6. A machine as claimed in any of the above claims and wherein mechanical means is provided supporting one of said two bodies from the other.

7. A machine as claimed in any of claims 1 to 5 and wherein a further plurality of electro-magnetic means are arranged around a second circle, concentric with said first mentioned circle, to produce.

when energised lines of force cutting said surface of said one body and a radial force in opposition to a radial force produced by said first mentioned plurality of electro-magnetic means and tending to produce relative lateral motion between said two bodies.

8. A machine as claimed in claim 7 and wherein each of said further dectro-mag- netic means comprises a coil and core assembly.

9. A machine as claimed in claim 8 and wherein for each electro-magnetic coil around said first mentioned circle, a radially aligned electro-magnetic coil is provided in said second circle.

10. A machine as claimed in any of the above claims and wherein said one body comprises magnetic material.

11. A machine as claimed in any of the above claims 1 to 9 and wherein said one body comprises non-magnetic material into which eddy currents are introduced due to said lines of force cutting said surface of said one body.

12. A machine as claimed in any of the above claims 1 to 9 and wherein said one body comprises a spherical coil, wound in squirrel cage fashion.

13. A machine as claimed in any of the above claims wherein means are provided for varying the voltage and phase of the supply to at least one of said electo-magnetic means.

14. A machine as claimed in any of the above claims, and wherein either said one body or said other body is fixed relative to a reference surface.

15. A machine as claimed in claim 14 and wherein said other member or said one member, as the case may be, carries, or is provided to carry, apparatus which is required to be rotated about an axis relative to said reference surface.

16. A machine as claimed in claim 15 and wherein said last mentioned apparatus is an aerial system.

17. A machine for providing relative rotational motion between two bodies substantially as herein described with reference to Figures 1 and 2 of the drawings accompanying the Provisional Specification.

18. A machine for providing relative rotational motion between two bodies substantially as herein described with reference to Figure 3 of the drawings accompanying the Provisional Specification.

19. A machine for providing relative rotational motion between two bodies substantially as herein described with reference to Figures 4 and 5 of the drawings accompanying the Provisional Specification.