A ROTOR POSITION SENSOR SYSTEM FOR A SLOTLESS MOTOR

Abstract

The present invention relates to a slotless motor comprising a rotor position sensing element. The motor has a rotor having a shaft of rotation and a plurality of coil windings arranged in an integer N of distinct blocks, each block being arranged around the shaft of rotation and having a space between each pair of adjacent blocks. The rotor position sensing element has a sensing ring having a sensor fixed to the sensing ring and a sensing ring attachment extending from the sensing ring, wherein the sensors are spaced around the shaft of rotation and wherein the rotor position sensing element is configured to hold the sensing ring relative to at least one of the blocks, such that the sensor is held in a predetermined position.

Description

A ROTOR POSITION SENSOR SYSTEM FOR A SLOTLESS MOTOR Field of invention The present invention relates to a slotless motor with improved rotor positioning. More particularly, but not exclusively, the present invention relates to a rotor position sensing element for a slotless motor. Background of the invention It is well known that the position of the rotor, a moving part of a motor, relative to the stator, a stationary part of a motor, plays a fundamental role in the motor's operation. Precise and accurate rotor positioning is necessary to ensure that the motor operates efficiently during startup and throughout its entire revolutions per minute (RPM) range. Many variations of different motor configurations are known, most of which fall into two categories: slotted motors and slotless motors. Both configurations have a stator comprising coil windings and a rotor, both enclosed within a motor housing. The stator, commonly made of steel laminations, is arranged to surround the rotor. The rotor comprises permanent magnets and is configured to rotate around its axis of rotation. The coil windings, commonly made of copper, are wound in the air gap between the rotor and the stator. The coil windings typically comprise a series of electromagnetic phases, with each phase energized through current outputs from a motor controller. In slotted motors, the stator is positioned around the rotor and consists of slotted laminations stacked together where the motor's coil windings are inserted into these slots (sometimes called teeth). In a slotless motor, the stator is positioned around the rotor, but there are no slotted laminations, and the motor's coil windings are wound around the rotor and positioned in the air gap between the rotor and stator. In a slotless motor, the phase windings are wound in such a way that each phase is repeated around the rotor with rotational symmetry, where each phase is separated from the subsequent phase winding by the other phases. For example, in the case of three phases: A, B, and C, the repeating phase winding pattern would be ABC, ABC, ABC, and so on. This pattern is separated around the rotor in such a way that the order in which each phase winding is energized generates torque on the rotor due to the interaction between the magnetic field generated in the coils and the permanent magnets in the rotor. For this to work, the precise position of the rotor relative to the stator windings must be known in order to energize the appropriate phase at the appropriate point during the rotor's rotation, even when the rotor is stationary.This interaction controls the direction and speed at which the rotor turns and is fundamental to motor control. Although this interaction has been described in terms of a rotor comprising permanent magnets, it would be understood that torque is generated similarly with other types of rotors, for example, a rotor for a reluctance motor. In a slotted motor, the rotor position sensor is typically located on or between the stator teeth, whereas providing a sensor for a slotless motor can present a greater challenge due to the lack of stator teeth. This is because the rotor position sensor must be positioned so that it is fixed relative to the rotor and stator windings to provide an accurate reading. In either case, the tolerances of the measurements of the stator, rotor, and motor housing relative to each other are vital for providing accurate and highly precise rotor position readings. The present invention seeks to solve the aforementioned problems. Brief description of the invention The aspects of the invention are those set forth in the independent claims, and the optional features are set forth in the dependent claims. The aspects of the invention may be provided in conjunction with each other, and the features of one aspect may be applicable to other aspects. According to a first aspect of the invention, a slotless motor is provided comprising: a rotor with a rotating axis; a plurality of coils arranged in an integer number N of distinct blocks, each block being arranged around the axis of rotation and having a space between each adjacent pair of blocks; and a rotor position sensing element comprising: a sensor ring having a sensor fixed to the sensor ring; and a sensor ring attachment extending from the sensor ring; wherein the sensors are separated about the axis of rotation; and wherein the rotor position sensor element is configured to hold the sensor ring relative to at least one of the blocks, so that the sensor is held in a predetermined position. The plurality of coils is arranged in blocks; for example, each block of the plurality of coils has a space between it and the adjacent blocks, so that when a current is applied to a particular block, it becomes electromagnetically energized and generates a torque within the rotor, causing it to rotate toward that energized block. This torque can be generated by an interaction between the magnetic field of the blocks and the magnetic field of a permanent magnet rotor, or by the reluctance of a reluctance rotor. By holding the rotor position sensing element relative to a particular block of coil windings, the sensing ring remains fixed relative to the rotor and can provide a reference point for the current rotor position relative to the coil winding block.For example, the rotor positioning can be provided as the rotation angle of a particular point on the rotor relative to the reference block. In some examples, the sensor ring fitting is configured to engage one of the gaps between adjacent blocks. Once the rotor position relative to a coil winding reference block is known, it is possible to determine which block should be energized to generate the torque on the rotor to cause it to rotate. In some examples, the motor further comprises a motor housing, where the housing may contain the coil windings in a fixed location relative to the housing. In some examples, the motor housing is formed from a composite material, for example, comprising a metallic material, and in some examples, the housing is metallic. In some examples, the sensing ring may be coupled to the motor housing. The rotor position sensing element is held relative to the coil blocks and the motor housing. The motor housing may comprise a proximal end cap and a distal end cap, and the sensing ring may be coupled to one of the end caps. For example, the sensing ring may have a node that only allows it to be coupled to the motor housing in a predetermined orientation. In some examples, the sensor ring may be integrally formed with the motor housing. For instance, the sensor ring may be integrally formed with an end cap of the motor housing. This can be achieved, for example, by casting the motor housing and the sensor ring as a single piece. In some examples, this is achieved by welding, bonding, or some other method of fusing the sensor ring to the motor housing. In some examples, the sensor ring fittings may be integrally formed with the motor housing, and the sensor ring may be mated to the motor housing. Mating the sensor ring and / or the sensor ring fittings to the motor housing means that the sensor in the sensor ring is aligned with the motor housing, as well as with the stator, and is held fixed relative to the rotor. According to a second aspect of the invention, a rotor position sensing element for a slotless motor is provided, comprising a rotor having a rotation axis and a plurality of coils, wherein the coils are arranged in N distinct coil blocks having a space between each pair of adjacent blocks, the rotor position sensing element comprising: a sensing ring comprising at least one sensor fixed to the sensing ring and configured to be spaced about the rotation axis; and a sensing ring attachment extending from the sensing ring and configured to hold the sensing ring relative to at least one of the blocks such that the sensing ring or sensing rings are held in position with respect to the blocks. In some examples, the sensor is any of: a magnetic field sensor, for example, a Hall effect-based position sensor or a magnetostrictive position sensor, a potentiometric position sensor, an inductive position sensor, an eddy current-based position sensor, a capacitive position sensor, a fiber optic position sensor, an optical position sensor, and an ultrasonic position sensor. In some examples, the rotor position sensor element comprises a plurality of sensors. For example, the plurality of sensors are angularly separated around the axis of rotation based on one or more distinct block numbers and / or a number of coil winding phases. By doing so, it is possible to identify which of the equivalent coil locations is closest to a particular point on the rotor.The term equivalent coil location refers to the znbQLn / zznz / e / Yi direction of the magnetic field induced in the coil windings and, in the case of windings having a plurality of phases, a corresponding phase or a corresponding phase and direction of the magnetic field induced in the coil windings, i.e., a coil winding of a particular phase in one block has an equivalent coil location to a coil winding driven in the same phase in a different block, although the direction of the induced magnetic field may or may not be different. In some examples, the sensor ring and the sensor ring accessory are integrally formed. In some examples, each distinct block includes a positive integer X of coil winding phases. Preferably, each block comprises three coil winding phases. For example, the angular position of greatest flux magnitude for each winding is separated from the angular positions of greatest flux magnitude of adjacent windings by an angle of π / NX radians, where N is the number of distinct blocks and X is the number of phases in a block. This separation corresponds to the maximum flux and the strongest point in the magnetic field generated by the current passing through a particular coil winding phase at different angular locations, regardless of the direction of the induced magnetic field. It should be noted that in some examples where the blocks are substantially identical, the angular separation between blocks (e.g., the same point on each block, such as the center-to-center distance of two adjacent blocks) is 2π / N radians, where N is the total number of blocks. This is consistent with the separation of π / NΧ radians between equivalent blocks because there are also two directions of induced magnetic field, P, related to the windings wound in a first and second direction, which any given block can have. Taking this into account, the complete expression for the rotation angle of an equivalent block is therefore 2π / NΡΧ, where P = 2, thus arriving at the previous expression π / NΧ. In some examples, each coil winding in each block comprises a repeated winding pattern such that each phase winding is wound in a first direction and then consecutively wound in a second direction opposite to the first. In some examples, each block would have a phase pattern X in a first direction followed by a phase pattern X in a second direction opposite to the first, i.e., (Af, Bf, Cf, Aj, Bj, Cj) is a winding pattern, etc., where A, B, and C represent distinct phases and the arrows (f and j) represent the direction of the induced magnetic field in the coil winding. It should be noted that the direction of the arrows is arbitrary, simply indicating that two given coils are arranged to have the same direction of induced magnetic field when their arrows are equal and opposite directions of induced magnetic field when their arrows are opposite.Thus, in the previous example pattern, Af and Aj share a phase, but when energized, their magnetic fields point in opposite directions. This can be considered as being 180 degrees out of phase with each other when sinusoidally varying currents are applied. In some examples, the number N of distinct blocks has a rotational symmetry of N times about the axis of rotation, such that equivalent locations on each block are separated by 2π / N radians. In other words, each block has an identical configuration separated znbQLn / zznz / e / Yi uniformly around the axis of rotation such that, from any given starting point, rotations of an angle calculated as any positive integer multiplied by 2π / N radians lead to an equivalent coil location. In some examples, the plurality of sensors is separated from each other by an angle, in radians, of: znbQLn / zznz / e / Yi where n is any integer and m is any integer except 0 or pXy where p is any integer. This points to any location around the rotational symmetry of the coil winding, either clockwise, i.e., positive integer values ​​for p or counterclockwise, i.e., negative integer values ​​for p. In some examples, the plurality of sensors is separated from each other by an angle, in radians, of: where n is any integer and m is any integer except 0 or 2pX, and where p is any integer. This equation refers to any location around the rotational symmetry of the coil winding in a particular phase and direction of the induced magnetic field. In some examples, there is an additional asymmetric shift applied to part of the sensor separation, δ, which ensures that some sensors are placed offset from equivalent coil locations, even when all coils are uniformly separated around a rotational symmetry.This provides information about the current position of the rotor relative to the coils, for example, the point of greatest flux in a particular phase and the direction of the coil winding (for example, sensors that are not offset), as well as information about how a particular point on the rotor is offset relative to the next coil winding, for example, the next largest flux magnitude in a particular direction of the coil winding of a phase. In some examples, in addition to the equation above, some or all of the sensors are offset asymmetrically by some factor, δ. The asymmetric offset factor, δ, can be different for different pairs of sensors to obtain additional and more nuanced information in accordance with the general principles of asymmetric offsets discussed earlier. In some examples, the sensor ring attachment is configured to fit into the space between adjacent blocks. In some examples, one end of the sensor ring attachment is configured to stay in the space between adjacent blocks. In some examples, the rotor position sensing element comprises a plurality of sensing ring fittings, each configured to engage a different gap between adjacent blocks. In some examples, at least one of the plurality of sensors is held in a fixed position relative to the sensor ring accessories. In some examples, the sensor ring fittings are shaped like a tapered projection. For example, the tapered projection is shaped to match the gap between adjacent coil winding blocks. Brief description of the drawings The methods of disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a slotless motor with a rotor position sensing element assembly. Figure 2 shows an exploded view of an example of a slotless motor comprising a rotor position sensing element. Figure 3a shows exemplary individual coil winding wires forming a coil winding block for a slotless motor. Figure 3b shows exemplary coil windings for a slotless motor. Figure 4a shows a perspective view of a sensor ring and a sensor ring attachment coupled to an end cap of the motor. Figure 4b shows a front view of a sensor ring and sensor ring accessories attached to an end motor cover. Detailed description of the invention The embodiments of the claims relate to a slotless motor with a precise rotor positioning measurement system. In particular, the embodiments of the claims relate to a rotor position sensor element comprising a sensor ring and a sensor ring attachment that holds the sensor ring fixed relative to the coil windings, which can be used, for example, in a slotless motor comprising a stator comprising coil windings and a rotor comprising permanent magnets. As a result, the system can help provide more precise motor control, thereby increasing motor efficiency. Figure 1 shows a system 100 comprising a slotless motor 110 and a rotor position sensor assembly 111. The rotor position sensor assembly comprises the sensor connector 112 and connector pin 120 for connection to a motor controller (not shown). The sensor connector 112 is configured to engage with the sensor ring in order to transfer the sensor signals to the motor controller via the connector pin 120. This embodiment shows a wired connection between the sensor connector 112 and the connector pin 120; however, it is understood that the transfer of sensor data can be achieved via a wireless connection, for example, via Bluetooth™ or Wi-Fi™, where the sensor connector comprises a wireless module configured to communicate with a wireless module coupled to the sensor connector. Figure 2 shows an example of an exploded view of a slotless motor assembly 200 znbQLn / zznz / e / Yi comprising a slotless motor 210 comprising a rotor position sensing element 217, 218, 219. Figure 2 shows a slotless motor 210 comprising a motor housing with heat sink 213, stator 205, a sensing ring fitting 217, sensing ring 219, sensor printed circuit board (RGB) 218 ​​and motor housing end cap 201. The stator 205 comprises a coil winding assembly 206 having a plurality of coil windings arranged in separate blocks 206a, 206b, and further comprises a flux ring 208 encompassing the coil winding assembly. All of these components, in this example, are contained within a motor housing with a heat sink 213. Providing a heat sink in the motor housing helps regulate the temperature of the motor itself. It will also be appreciated that the addition of a flux ring increases the strength of the magnetic field generated when a current passes through the coil windings. Each of the distinct blocks 206a, 206b of the coil winding assembly 206 has a space between adjacent blocks 206a, 206b. The rotor 203, which is rotatable about a rotation axis P, has separate permanent magnets 203a, 203b around its circumference and is positioned within the stator 205 and the motor housing 213 such that it is completely contained within the stator 205. The rotation axis P extends through the center of the entire motor assembly, and in this example, the plurality of distinct blocks 206a, 206b are spaced about the axis P in a rotational symmetry of N times, where N is the number of distinct blocks 206a, 206b. In this example, the sensor ring 219 together with the sensor ring accessory 217 and the sensor PCB 218 constitute the rotor position sensing element 217, 218, 219. The sensor ring 219 comprises at least one sensor capable of detecting the magnetic field of the magnets 203a, 203b on the rotor 203. The sensor PCB 218 may provide basic circuitry to the sensor in the sensor ring 219 and provide a mating point for the sensor connector 112. In some embodiments, the sensor is one of the following: a magnetic field sensor, for example, a Hall effect-based position sensor or a magnetostrictive position sensor, a potentiometric position sensor, an inductive position sensor, an eddy current-based position sensor, a capacitive position sensor, a fiber optic position sensor, an optical position sensor, and an ultrasonic position sensor.In some embodiments, the sensor PCB 218 may be housed in the sensor connector 112, which is configured to engage the sensor ring 219 and receive sensor readings. The sensor ring fitting 217 is configured to hold the rotor position sensor element 217, 218, 219 relative to at least one of the distinct blocks, so that the sensor is held in a predetermined location relative to the stator 205 and the coil winding assembly 206. The sensor ring fitting 217 may have a tapered projection that can be configured to fit in a gap between the adjacent blocks 206a, 206b. The rotor position sensor element 217, 218, 219 is also engaged with the motor end cap 201 so that the motor length does not increase with the addition of the rotor position sensor element.It will be noted that although three sensor ring fittings are shown, it is possible to keep the rotor position sensing element in a fixed position using one or a plurality of sensor ring fittings where each of the plurality of znbQLn / zznz / e / Yi sensor ring fittings is configured to fit in a different space between adjacent blocks. During normal motor operation, a magnetic field is generated in the stator, causing the rotor to rotate around its axis of rotation. The sensor in sensor ring 219 measures the magnetic field produced by the coils in the rotor 203. The characteristics of the magnetic field measurement provide details about the rotor's current orientation, i.e., the magnetic field polarity, field strength, etc. Once the rotor 203's orientation is known, it is possible to determine which phase and associated coils in the windings should be energized to create the torque on the rotor 203 necessary to make it rotate in the desired direction and at the desired speed.For example, in the case of a permanent magnet rotor, a permanent magnet in the rotor 203 with a north pole directed radially outward can generate a magnetic field in the sensor region. This magnetic field has a specific polarity—in this example, north—and a strength that depends on the distance between the magnet and the sensor, as well as the magnet's strength. This north pole can be the magnet closest to the sensor, which can then transmit information to a motor controller. Although this working example has been described in the context of a permanent magnet rotor, those skilled in the art would understand that other rotor configurations can also be used with an appropriate sensor. Since the orientation of the sensor ring 219 comprising the sensor is fixed relative to the stator 205, in this example, through the coil winding assembly 206 and the sensor ring accessories, the motor control system can determine the position and orientation of the rotor 203 with respect to the stator. It can then supply current to energize the appropriate coil windings 206 with the correct polarity to generate torque on the rotor 203, causing it to rotate. Figures 3a and 3b show an example of coil windings in a slotless motor. The individual coil wires 301a to 301n are coupled together to form coil winding blocks 302 around the motor's axis of rotation P, forming the coil assembly with a first axial end and a second axial end. The way in which the blocks 302a, 302b, 303c are wound produces a gap between adjacent blocks at the first axial end 302a, 302b, 302c and at the second axial end 304a, 304b of the coil windings. In some embodiments, the coil windings comprise a positive phase of integer X, where each block 306a, 306b, 306c comprises a different phase. In some embodiments, each distinct block 306a, 306b, 306c may include a positive integer X number of coil winding phases. In preferred embodiments, each block 306a, 306b, 306c comprises three coil winding phases.That is, each individual coil wire 301a to 301n is configured to carry current in one of the phases. In some embodiments, each individual coil wire is configured to carry current in a different phase than an adjacent coil wire. In either case, the individual coils are wound in a first direction toward the first axial end 302, forming a block, and then wound in a second direction toward the second axial end 304, also forming a block. This allows each coil in the same phase to be in series. As each coil wire is energized, a magnetic field is created, and the angular position of greatest flux magnitude for each winding is separated from the angular positions of greatest flux magnitude of adjacent windings by an angle of π / NX radians, where N is the number of distinct blocks and X is the number of phases in a block. A sensor measurement at or near these points would be indicative of the maximum torque that can be generated at a given rotor position and orientation. This is because the point of greatest flux magnitude is the point at which the magnetic field is strongest, which will create the greatest torque on the rotor—for example, in the case of a permanent magnet rotor, to force the appropriate magnetic pole into alignment with the magnetic field generated by the coils.This would also apply to a reluctance motor where the flux barriers in the rotor for a reluctance motor would force the rotor to align with the magnetic field lines generated by the coils. In the configuration shown in Figures 3a and 3b, each block comprises a repeated winding pattern such that each phase winding is wound in a first direction and then consecutively wound in a second direction opposite to the first. Therefore, each block would have a phase pattern X in a first direction of the induced magnetic field followed by a phase pattern X in a second direction of the induced magnetic field opposite to the first, i.e., (Af, Bf, Cf, A1, B2, C3), where the arrows represent the direction of the induced magnetic field. The number N of distinct blocks has N-fold rotational symmetry about the rotation axis P such that the equivalent locations on each block are separated by 2π / N radians.In other words, each block has an identical configuration evenly spaced around the axis of rotation such that, from any given starting point, rotations of an angle calculated as any positive integer multiplied by 2π / N radians result in an equivalent coil location. Figures 4a and 4b show a perspective and front view of an example of a motor housing end cap 401 comprising a rotor position sensing element. In this example, the end cap 401 and the sensing ring fittings 417a, 417b are integrally formed. The sensing ring 419 may comprise the node 421, which is configured to engage with a hole of the corresponding shape and size in the end cap, so that the sensing ring 419 is coupled to the end cap in a predetermined manner. In some embodiments, the sensing ring fittings 417a, 417b and / or the sensing ring 419 may be milled or cast with the motor end cap 401. In some embodiments, the sensing ring fittings 417a, 417b and / or the sensing ring 419 may be coupled to the motor end cap 401 by welding, bonding, or some other means of fusing the two components. Because the rotor position sensing element 419, 417 is attachable to the motor end cap 401, the rotor position sensing element can be held in a fixed position relative to the motor housing 213. Therefore, the rotor position sensing element 417, 419 can be held fixed relative to the stator coil windings, wherein the rotor position elements are tapered to fit in the space between two adjacent coil winding blocks 306a, 306b. In some embodiments, the shape of the sensing ring fittings 417a, 417b is designed to fit in the spaces between adjacent coil winding blocks 306a, znbQLn / zznz / e / Yi 306b. By keeping the rotor position sensing element 417, 419 fixed relative to the stator, the sensors can be positioned at predetermined locations relative to a particular phase of a coil winding or coil winding block. The rotor position readings provided to the motor controller thus show the position of the rotor relative to the stator. In other words, the rotor position sensing element is held relative to at least one, and in some cases all, of the stator coil windings, the rotor's axis of rotation, and the motor housing overall. Advantageously, any measurements made by the rotor position sensing elements can be completed with a higher level of precision and accuracy, since the readings are less affected by the dimensional tolerances of the motor mounting components. In the context of this disclosure, other examples and variations of the systems described herein will be evident to a person skilled in the art. From the foregoing analysis, it will be appreciated that the modalities shown in the figures are merely illustrative and include features that can be generalized, eliminated, or replaced as described herein and as set forth in the claims.

Claims

1. A slotless motor comprising: a flux ring; a rotor having a rotation axis; a plurality of coil windings arranged in an integer number N of distinct blocks, each block being arranged around the rotation axis and having a space between each adjacent pair of blocks; and a rotor position sensing element comprising: a sensing ring having a sensor fixed to the sensing ring; and a sensing ring attachment extending from the sensing ring; wherein the sensing rings are spaced around the rotation axis; and wherein the rotor position sensing element is configured to hold the sensing ring relative to at least one of the blocks, so that the sensing ring is held in a predetermined position.

2. The motor according to claim 1, wherein the sensor ring attachment couples the sensor ring to one of the spaces between the adjacent blocks.

3. The motor according to claim 1 or 2, further comprising a motor housing, wherein the housing holds the coil windings in a fixed location relative to the housing.

4. The motor according to claim 3, wherein the sensor ring is coupled to the motor housing.

5. The motor according to claim 3, wherein the sensor ring is integrally formed with the motor housing.

6. The motor according to claim 3, wherein the motor housing is made of a metal.

7. A rotor position sensing element for a slotless motor comprising a rotor having a rotation axis and a plurality of coil windings wherein the coil windings are arranged in N distinct blocks of coil windings having a space between each pair of adjacent blocks, the rotor position sensing element comprising: a sensing ring comprising at least one sensor fixed to the sensing ring and configured to be spaced about the rotation axis; and a sensing ring attachment extending from the sensing ring and configured to hold the sensing ring relative to at least one of the blocks, so that the sensors are held in position relative to the blocks.

8. The motor or rotor position sensor according to any of the preceding claims, wherein the sensor is any of: a magnetic field sensor, a potentiometric position sensor, an inductive position sensor, an eddy current-based position sensor, a capacitive position sensor, a fiber optic position sensor, an optical position sensor, and an ultrasonic position sensor.

9. The motor or rotor position sensing element according to any of the preceding claims, wherein the rotor position sensing element comprises a plurality of sensors.

10. The motor or rotor position sensing element according to claim 9, wherein the plurality of sensors is angularly separated around the axis of rotation based on one or more of the distinct block numbers and / or a number of coil winding phases.

11. The motor or rotor position sensing element according to any of the preceding claims, wherein the sensing ring and the sensing ring attachment are integrally formed.

12. The motor or rotor position sensing element according to any of the preceding claims, wherein each block includes a positive integer number X of coil winding phases.

13. The motor or rotor position sensing element according to claim 12, wherein a higher flux magnitude angular position for each winding is separated from the higher flux magnitude angular positions of adjacent windings by an angle of π / NΩ radians.

14. The motor or rotor position sensing element according to any of the preceding claims, wherein each coil winding in each block comprises a repeated winding pattern such that each phase winding is wound in a first direction and is subsequently wound in a second direction opposite to the first direction.

15. The motor or rotor position sensing element according to any of the preceding claims, wherein the number N of distinct blocks has a rotational symmetry of N times about the axis of rotation such that equivalent locations on each block are separated by 2π / N radians.

16. The motor or rotor position sensing element according to claim 13 dependent on claim 9, wherein each sensor is separated from each other by an angle in radians of: znbQLn / zznz / e / Yi where nes is any integer and mes is any integer except 0 or pXy where p is any integer.

17. The motor or rotor position sensing element according to claim 13 dependent on claim 9, wherein each sensor is separated from each other by an angle in radians of: where n is any integer and m is any integer except 0 or 2pXy where p is any integer.

18. The rotor position sensing element according to any of claims 7 to 17, wherein the sensing ring attachment is configured to engage the space between adjacent blocks.

19. The rotor position sensing element according to claim 18, wherein one end of the sensing ring fitting is configured to be held in the space between adjacent blocks.

20. The rotor position sensing element according to any of claims 7 to 19, comprising a plurality of sensing ring fittings, each configured to engage a different gap between adjacent blocks.

21. The rotor position sensing element according to any of claims 7 to 20, wherein at least one of the plurality of sensors is held in a fixed position relative to the sensor ring attachment.

22. The motor or rotor position sensing element according to any of the preceding claims, wherein the sensing ring fittings are formed as a conical projection.

23. The motor or rotor position sensing element according to claim 22, wherein the conical projection is formed to match the shape of the space.

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