GB2587414A

GB2587414A - Actuator Assembly

Info

Publication number: GB2587414A
Application number: GB1914016.9A
Authority: GB
Inventors: Langhorne Robert; Howarth James; Pantelidis Konstantinos; John Reynolds Matthew; South Adam
Original assignee: Cambridge Mechatronics Ltd
Current assignee: Cambridge Mechatronics Ltd
Priority date: 2019-09-27
Filing date: 2019-09-27
Publication date: 2021-03-31
Anticipated expiration: 2039-09-27
Also published as: GB201914016D0; GB2587414B

Abstract

An actuator assembly e.g. for a miniature camera comprises a main body 10, a moveable part 20 having an aperture configured to receive an auxiliary component such as a lens (not shown), and a plurality of lengths of shape-memory alloy (SMA) wire connected between the main body 10 and the moveable part 20. The lengths of wire are configured, when selectively powered, to cause three-dimensional movement of the movable part 20 relative to the main body 10. A mechanism 50 increases the stiffness of the moveable part 20 so as to reduce distortion of the aperture 20a when the lengths of wire are powered to position the movable part 20 for receiving the auxiliary component, and hence facilitate assembly of the lens. The stiffening mechanism may comprise a reinforcing e.g. metallic ring 50 which may be circular, polygonal or other shapes. Alternatively, engaging features may be provided to selectively stiffen the moveable part (figures 9-14).

Description

ACTUATOR ASSEMBLY

Field

The present application relates to an actuator assembly, particularly an actuator assembly comprising a plurality of lengths of shape-memory alloy (SMA) wire.

Background

WO 2011/104518 Al describes an actuator assembly that uses SMA wires to move a movable part relative to a main body, for example to provide autofocus and optical image stabilisation. Eight SMA wires are arranged inclined with respect to a notional primary axis with a pair of the SMA wires on each of four sides around the primary axis. The SMA wires are connected so that, on contraction, two groups of four SMA wires provide forces with components in opposite directions along the primary axis. The SMA wires of each group have 2-fold rotational symmetry about the primary axis. Hence the SMA wires are capable of causing three-dimensional movement of the movable part relative to the main body.

Such an actuator assembly can be used in a miniature camera module. As part 20 of the process of assembling such a camera module, a camera lens is attached to the moveable part.

Summary

According to a first aspect of the present invention, there is provided an actuator assembly comprising: a main body; a moveable part having an aperture configured to receive an auxiliary component; a plurality of lengths of shape-memory alloy wire connected between the main body and the moveable part, wherein the lengths of wire are configured, when selectively powered, to cause three-dimensional movement of the movable part relative to the main body; and a mechanism configured, when the lengths of wire are selectively powered to position the movable part for receiving the auxiliary component, to enable the stiffness of the moveable part to be increased so as to reduce distortion of the aperture.

Thus, the movable part can be positioned for receiving the auxiliary component (which may correspond to a lens) in such a way that the process of attaching the auxiliary component to the actuator assembly can be carried out more accurately.

Optionally, the mechanism is configured to reduce deformation of the movable part towards and/or away from an axis through the aperture.

Optionally, the mechanism comprises one or more stiffening elements. Optionally, the stiffening elements are connected to the movable part and comprise a material having a higher elastic modulus than that of the moveable part.

Optionally, at least one of the stiffening elements is ring-shaped and encircles the aperture.

Optionally, the stiffening elements are positioned within the aperture and/or on at least one major surface of the moveable part.

Optionally, at least one of the stiffening elements is a collar within the aperture.

Optionally, the stiffening elements comprise a set of stiffening elements, each of which is positioned in a region of relatively high stress in the moveable part when the lengths of wire are selectively powered.

Optionally, the actuator assembly comprises one or more resilient elements connected between the main body and the moveable part, wherein at least one of the stiffening elements and the one or more resilient elements together form part of a unitary component.

Optionally, the actuator assembly comprises one or more crimps for connecting 35 the lengths of shape-memory wire to the moveable part, wherein at least one of the stiffening elements and the one or more crimps together form part of a unitary component.

Optionally, the unitary component is formed from a sheet material.

Optionally, the mechanism comprises one or more features configured to couple the movable part to a removable frame.

Optionally, the frame comprises a plurality of arms and each of the features is configured to couple a region of the movable part to one of the arms.

Optionally, each of the regions corresponds to a region of relatively high stress in the moveable part when the lengths of wire are selectively powered.

Optionally, each of the arms is resilient and each of the features is configured to couple to an arm in such a way that the arm applies a biasing force at the region, wherein the biasing force counteracts the force at the region due to the lengths of wire being selectively powered.

Optionally, the forces at the regions due to the lengths of wire being selectively powered are directed towards and/or away from the axis through the aperture.

Optionally, the mechanism comprises one or more protrusions on the surface of the movable part within the aperture, the one or more protrusions configured to transfer stress to the auxiliary component.

Optionally, the protrusions are positioned in regions where the forces due to the lengths of wire being selectively powered are directed towards the axis through the aperture.

Optionally, the mechanism comprises one or more features configured to couple the movable part to the main body via one or more removable wedges, wherein each wedge comprises one or more one or more protrusions for contacting the movable part and/or the main body.

Optionally, the wedges are couplable to regions of the movable part where the forces due to the lengths of wire being selectively powered are directed away from the axis through the aperture.

Optionally, the movable part is polygonal and at least two apexes of the polygonal movable part have a crimp attached thereto for connecting the lengths of wire to the polygonal moveable part.

Optionally, the regions of the movable part where the forces due to the lengths of wire being selectively powered are directed towards the axis through the aperture correspond to the at least two apexes. Optionally, the regions of the movable part where the forces due to the lengths of wire being selectively powered are directed away from the axis through the aperture correspond to apexes intermediate to the at least two apexes.

There may be provided a camera assembly comprising the actuator assembly, wherein the auxiliary component comprises a lens.

There may be provided a kit comprising the actuator and the removable frame.

There may be provided a kit comprising the actuator and the removable wedges.

According to a second aspect of the present invention, there is provided a method of attaching an auxiliary component to the actuator assembly, the method comprising: selectively powering the lengths of wire to position the movable part; and introducing the auxiliary component into the aperture of the moveable part.

Optionally, the method comprises: coupling the frame to the movable part before selectively powering the lengths of wire to position the movable part; and removing the frame after attaching the auxiliary component to the movable part.

Optionally, the method comprises: coupling the movable part to the main body via the one or more wedges before selectively powering the lengths of wire to position the movable part; and removing the wedges after attaching the auxiliary component to the movable part.

Brief Description of the Drawings

Certain embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of (a) an example of a stiffening element for a lens carriage of an actuator and (b) a first example of an actuator assembly including the stiffening element; Figure 2 is a perspective view of a second example of an actuator assembly including a stiffening element; Figure 3 is a perspective view of a third example of an actuator assembly C\I including two stiffening elements; Figure 4 is a perspective view of a fourth example of an actuator assembly including a non-round stiffening element; CY)20 Figure 5 is a perspective view of a fifth example of an actuator assembly CD including a cylindrical stiffening element; Figure 6 is a perspective view of a sixth example of an actuator assembly including local stiffening elements; Figure 7 is a perspective view of (a) a combined stiffening and spring element 25 and (b) a seventh example of an actuator assembly including the combined element; Figure 8 is a perspective view of an eighth example of an actuator assembly including a combined stiffening and crimp element; Figure 9 is a perspective view of a ninth example of an actuator assembly including a stiffening element providing a tensile force on the lens carriage; Figure 10 is a perspective view of a tenth example of an actuator assembly including a stiffening element providing a compressive force on the lens carriage; Figure 11 is a perspective view of an eleventh example of an actuator assembly including a stiffening element providing tensile and compressive forces on the lens carriage; Figure 12 is (a) a partial perspective view of the lens carriage of a twelfth example of an actuator assembly including a feature for reducing inwards distortion and (b) a partial cross-sectional view of a part of the actuator assembly; Figure 13 is (a) a perspective view of a removable element for reducing outwards distortion of a lens carriage and (b) a partial cross-sectional view of a thirteenth example of an actuator assembly including the said element; and Figure 14 is a perspective view of a reference example of an actuator assembly including a lens carriage.

Detailed Description

Reference example

Referring to Figure 14, a reference example of an actuator assembly 1 suitable for use in a miniature camera module will now be described.

The actuator assembly 1 includes a static part 10 and a moving part 20. The moving part 20 has an aperture 20a for holding a camera lens 25 (shown in Figure 4 only). Hence the moving part 20 is hereinafter referred to as a lens carriage. The camera lens 25 includes a lens or an assembly of lenses. The camera lens (hereinafter sometimes referred to as simply 'the lens') and hence the aperture 20a is cylindrical. As described in more detail below, the lens carriage 20 is supported on the static part 10 by eight SMA wires 30 (hereinafter referred to as simply 'the wires'). The lens carriage 20 is capable of movement with respect to the static part 10, driven by the wires 30, with up six degrees of freedom, i.e. three orthogonal translational degrees of freedom and three orthogonal rotational degrees of freedom.

The position and orientation of various features of the actuator assembly 1 can be conveniently described with reference to a primary axis 0 defined with reference to the static part 20. Broadly speaking, the primary axis 0 corresponds to an axis of (two-fold) rotational symmetry of the actuator assembly 1. The primary axis 0 typically corresponds to the optical axis of the lens 25. Hence the primary axis 0 is hereinafter referred to as the optical axis.

The actuator assembly 1 includes a set of e.g. two arms 5 (hereinafter referred to as spring arms) connecting the static part 10 to the lens carriage 20. The spring arms 5 provide an electrical connection from the static part 10 to the moving ends of the wires 30 (i.e. the ends of the wires 30 connected to the lens carriage 20) and/or provide a centring biasing force on the lens carriage 20 (e.g. when the wires 30 are unpowered).

The static part 10 includes a base plate 10a and two static posts 10b provided on opposite corners of the base plate 10a. The static posts 10b may be affixed to the base plate 10a or formed integrally with the base plate 10a as one piece. Two crimp assemblies 13 are affixed to each of the two static posts 10b. The base plate 10a is configured to hold an image sensor (not shown).

The lens carriage 20 includes two moving posts 20b aligned with the corners of the base plate 10a intermediate the static posts 10b. Two crimp assemblies 23 are affixed to each of the two moving posts 20b. The corners of the lens carriage 20 at which the moving posts 20b are positioned are hereinafter referred to as the crimp corners.

The lens carriage 20 is preferably formed of an injection-moulded plastics material.

The wires 30 are connected between the static part 10 and the lens carriage 20 by being crimped at one end to a crimp assembly 13 of the static part and at the other end to a crimp assembly 23 of the lens carriage 20. The crimp assemblies 13, 23 serve as both mechanical and electrical connections. The crimp assemblies 23 on the same moving post 20b are both electrically connected to one of the spring arms 5.

The wires 30 have the same configuration around the lens carriage 20 as the SMA wires in the actuator assembly described in W02011/104518 Al. Specifically, two wires 30 are arranged on each of four sides around the optical axis 0, and are inclined with respect to the optical axis 0 (i.e. at an acute angle greater than 0°) in opposite senses to each other and crossing each other, as viewed perpendicular to the optical axis 0. Thus, in particular, each of the wires 30 is inclined with respect to the optical axis 0 and with respect to each other. Reference is made to WO 2011/104518 Al for further details of the arrangement of the wires 30.

Selective contraction of the wires 30 can drive movement of the lens carriage 20 in any of the six degrees of freedom. Such movement is hereinafter sometimes referred to as three-dimensional (3D) movement. Contraction and expansion of the wires 30 is generated by selectively applying drive signals thereto. The wires are resistively heated by the drive signals and cool by thermal conduction to the surroundings when the power of the drive signals is reduced.

Thus, the wires 30 may be used to provide both an autofocus (AF) function by translational movement of the lens carriage 20 along the optical axis 0 and an optical image stabilisation (OIS) function by translational movement of the lens carriage 20 perpendicular to the optical axis 0.

The drive signals may be generated by a control circuit (not shown) and supplied to the wires 30. Such a control circuit may receive an input signal representing a desired position for the lens carriage 20 and generates drive signals having powers selected to drive the lens carriage 20 to the desired position. The power of the drive signals may be either linear or varied using pulse width modulation. The drive signals may be generated using a resistance feedback control technique, in which case the control circuit measures the resistance of the wires and uses the measured resistance as a feedback signal to control the power of the drive signals.

Assembling a camera module including the reference example Assembling a camera module with the abovedescribed actuator assembly 1 generally involves attaching the lens 25 to the lens carriage 20. An example way of carrying out this part of the process (hereinafter referred to as the lens attach process) will now be described.

The lens 25 may be attached to the lens carriage 20 in any suitable way, e.g. via a suitable adhesive and/or a threaded connection, etc. During the lens attach process, the wires 30 are powered so that the lens 25 can be attached to the lens carriage 20 at a desired position within the operational range of each of the wires 30 (e.g. at desired X, Y and Z-positions in a cartesian coordinate system in which the Z-axis coextends with the optical axis 0).

Powering the wires 30 transfers a load to, and causes stress in, the lens carriage 20. This can cause flexing of the lens carriage 20 and therefore distortion of the aperture 20a in which the lens 25 is to be held. This, in turn, can cause misalignment of the lens 25 in the lens carriage 20 and, in extreme cases, can even prevent insertion of the lens 25 altogether. In examples with a threaded connection between the lens 25 and the lens carriage, the distortion of the aperture 20a and hence the threads on the lens carriage 20 can cause increased resistance against tightening the lens 25 into place.

As illustrated in Figure 14, it is anticipated that the crimp corners of the lens carriage 20 will be pulled inwards by the wires 30 and the other corners will be pushed outwards during the lens attach process.

First set of examples Referring to Figures 1-8, several examples of actuator assemblies will now be described.

In each instance, the actuator assembly includes the same or similar features (identified with the same reference numbers) as the abovedescribed reference example. Furthermore, in each instance, the actuator assembly 11-81 includes at least one element (hereinafter referred to as a stiffening element) for stiffening the lens carriage 20.

First, second and third examples In first, second and third examples, the or each stiffening element is in the form of a ring 50 (hereinafter referred to as a stiffening ring) which is circular and encircles the aperture 20a in the lens carriage 20.

In the first example actuator assembly 11 (see Figure 1), the stiffening ring 50 is positioned within the aperture 20a. In this example, the stiffening ring 50 is set in a groove in the wall of the aperture 20a. Alternatively, the stiffening ring 50 may be affixed to the wall of the aperture 20af (which does not have a groove).

Instead of being formed of a single piece, the stiffening element 50 may be formed from multiple pieces, e.g. two half-circles, which are inserted into the aperture 20a (and held in the groove) and then welded/fused together to form a single piece. Thus, the stiffening ring 50 can be (readily) added after the lens carriage 20 has been moulded. Hence a potentially-undesirable insert-moulding process can be avoided.

Alternatively, the stiffening ring 50 may initially take the form of a broken ring which can be compressed to form a smaller-diameter ring, inserted into the aperture 20a, and then released so that its diameter increases to that of the (groove in the) aperture 20a. The break can then be e.g. welded or fused to form the final stiffening ring 50.

In variations of the first example, there may be multiple stiffening rings 50 within the aperture 20a.

In the second example actuator assembly 21 (see Figure 2), the stiffening ring 50 is affixed to the upper surface of the lens carriage 20 (i.e. the major surface further from the base plate 10a).

Alternatively, the stiffening ring 50 may affixed to the other major surface of the lens carriage 20, i.e. the lower surface.

In the third example actuator assembly 31 (see Figure 3), a first stiffening ring 501 is affixed to the upper surface and a second stiffening ring 502 is affixed to the lower surface of the lens carriage 20.

The stiffening ring(s) 50 is/are preferably made of a material that is more rigid than the material (e.g. injection-moulded plastic) of the lens carriage 20. For example, the stiffening ring material may have an elastic modulus that is 50 or ?100 times higher than that the lens carriage material. The stiffening ring(s) 50 is/are preferably made of steel, which has advantageous mechanical properties (e.g. an elastic modulus of -200 GPa), cost and manufacturability.

S

The stiffening ring(s) 50 is/are affixed to the lens carriage 20 in any suitable way, e.g. by way of adhesive, welding, and/or mechanical means.

Hence, the stiffening ring(s) 50 can increase stiffness of the lens carriage 20 so as to reduce the flexing of the lens carriage 20 and the distortion of the aperture 20a during the abovedescribed lens attach process. In some examples, the maximum distortion of the aperture 20a may be less than e.g. a few tens of microns, a few microns, or a few tenths of microns. Moreover, this can be achieved without undue negative effects on cost, performance, etc. Fourth and fifth examples In a fourth example (see Figure 4), the actuator assembly 41 is the same as in the second example except that the stiffening ring 50' has an octagonal shape.

Alternatively, the stiffening ring may have any non-circular shape which encompasses the aperture 20a.

In a fifth example (see Figure 5), instead of one or more stiffening rings 50 within the aperture 20a as in the first example, the actuator assembly 51 includes a stiffening element in the form of a collar 50" (e.g. a thin-walled hollow cylinder) within the aperture 20a.

The collar 50" preferably extends over most or all of the wall of the aperture 20a.

Similarly to the stiffening ring 50 in the first example, the collar 50" may be formed from multiple pieces or may initially have a break therein.

Sixth example

Instead of being used to reinforcing the entire circumference of the aperture 20a as in the abovedescribed examples, the stiffening element can be used to reinforce particular regions of the lens carriage 20, e.g. those regions which experience relatively high stresses during the wire attach process.

For instance, referring to Figure 6, in a sixth example actuator assembly 61, the stiffening element is formed of two semi-circular shaped pieces 51 in the non-crimp corners of the lens carriage 20, which may be regions that are particularly susceptible to deformation.

In some variations, the pieces 51 of the stiffening element may have a different shape, e.g. in the form of straight bars.

The pieces 51 of the stiffening element may be affixed to a surface of the lens carriage 25 or may be formed as an insert moulding.

Hence, the stiffening material can be used selectively in regions where it is most effective, advantageously enabling the total mass of stiffening material to be reduced.

Seventh example

As described above, the reference example actuator assembly 1 includes spring arms 5. In some examples, the stiffening element and the spring arms can form part of a single (unitary) component.

Referring to Figure 7, a seventh example actuator assembly 71 including such a component 52 will now be described.

Preferably, the stiffening element 52b and the spring arms 52a can be formed from a single sheet of material e.g. steel. This may be carried out e.g. by etching. The stiffening element 52b may be in the form of a ring. The component 52 can be affixed at the upper surface of the lens carriage 20, as illustrated in Figure 7(b), or may be positioned at least partly within the aperture 20a by insert moulding.

Eighth example

As described above, the reference actuator assembly 1 comprises one or more crimps 23 for connecting the lengths of shape-memory wire to the moveable part. In some examples, the stiffening element and the crimps 23 can form part of a single (unitary) component in a similar way to the sixth example.

Referring to Figure 8, in an eighth example, the actuator assembly 81 includes such a component/etching.

The crimps 23 are affixed to the side of the lens carriage 20 but the etching could be designed such that stiffening material could be incorporated and folded over onto the upper surface of the lens carriage 20.

The stiffening material could be a full ring or may be provided in selective regions as described above.

Ninth, tenth and eleventh examples Referring to Figure 9, a ninth example actuator assembly 91 will now be described.

In this example, a frame 53 picks up on faces in the lens carriage crimp corners. When the wires 30 are powered this frame 53 will hold the lens carriage 20 in tension, preventing these corners from being compressed inwards. After the lens 25 has been glued in place and the wires unpowered, the frame 53 can be removed and used again on another actuator 81.

The frame 53 does not need to be circular as in the figure. It could be rectangular, for instance. The frame 53 could sit at various heights and could conceivably be moved outboard of the actuator 81 to sit below the height of the actuator 81 if more space is required for lens insertion.

Referring to Figure 10, a tenth example actuator assembly will now be described.

Similarly to the ninth example, a frame 54 is made that can be inserted into e.g. holes in the lens carriage 20 in the non-crimp corners. This will hold the lens carriage 20 in these corners in compression, preventing them from being distorted outwards. After lens 25 has been glued in place and the wires unpowered, the frame 54 can be removed and used again on another actuator 81.

Referring to Figure 11, an eleventh example actuator assembly 111 combined elements from the ninth and tenth examples. Hence the frame holds the lens carriage 20 in all four corners, therefore preventing distortion

Twelfth example

Referring to Figure 12, a twelfth example actuator assembly 121 will now be described.

This concept involves incorporating a 'pip' into the central bore of the lens carriage moulding, in each of the crimp corners. These pips are small hemispheres.

If a lens is inserted and the wires then powered the pips will transfer the load of the wires through the lens carriage and into the lens. The lens will act as the stiffener preventing the distortion.

The pips are spherical to minimise the friction between the lens carriage and the lens which could impact upon the lens alignment.

This method will limit motion of the lens within the carriage for lens alignment in x and y, but tilt centering will still be possible.

Thirteenth example

Referring to Figure 13, a thirteenth example actuator assembly 131 will now be described.

In this example, wedges could be placed in the chassis corners between the chassis and the lens carriage. These wedges would have pips to pick up on the lens carriage, again to reduce the friction.

In these corners the lens carriage will want to distort outwards when the wires are powered. The wedges would limit this motion by transferring the load through to the chassis.

This method will limit motion of the lens carriage for lens alignment in x and y, but tilt centering will still be possible.

Other variations It will be appreciated that there may be many other variations of the above-described embodiments.

For example, the aperture could have features such as ribs to increase the stiffness. However, this would reduce the usable diameter of the aperture.

The lens carriage could be made of a stiffer material. This could be done by using a material other than an injection-moulded plastics or by adding stiffening fibres such as glass or carbon to the plastic.

The stiffening element may be used in other types of actuator assemblies, e.g. any type of actuator assembly in which a lens carriage is held (and potentially deformed) by selectively powered lengths of SMA wire while a lens is attached thereto.

The actuator assembly may be used in applications other than cameras. Instead of a lens, the movable part of the actuator assembly may be configured to hold another type of optical element or any auxiliary component.

The aperture need not fully extend through the movable part.

Claims

Claims 1. An actuator assembly comprising: a main body; a moveable part having an aperture configured to receive an auxiliary component; a plurality of lengths of shape-memory alloy wire connected between the main body and the moveable part, wherein the lengths of wire are configured, when selectively powered, to cause three-dimensional movement of the movable part relative to the main body; and a mechanism configured, when the lengths of wire are selectively powered to position the movable part for receiving the auxiliary component, to enable the stiffness of the moveable part to be increased so as to reduce distortion of the aperture.
2. An actuator assembly according to claim 1, wherein the mechanism is configured to reduce deformation of the movable part towards and/or away from an axis through the aperture.
3. An actuator assembly according to claim 1 or 2, wherein the mechanism comprises one or more stiffening elements, wherein the stiffening elements are connected to the movable part and comprise a material having a higher elastic modulus than that of the moveable part.
4. An actuator assembly according to claim 3, wherein at least one of the stiffening elements is ring-shaped and encircles the aperture.
5. An actuator assembly according to claim 3 or 4, wherein the stiffening elements are positioned within the aperture and/or on at least one major surface 30 of the moveable part.
6. An actuator assembly according to claim 5, wherein at least one of the stiffening elements is a collar within the aperture.
7. An actuator assembly according to any one of claims 3 to 6, wherein the stiffening elements comprise a set of stiffening elements, each of which is positioned in a region of relatively high stress in the moveable part when the lengths of wire are selectively powered.
8. An actuator assembly according to any one of claims 3 to 7, comprising one or more resilient elements connected between the main body and the moveable part, wherein at least one of the stiffening elements and the one or more resilient elements together form part of a unitary component.
9. An actuator assembly according to any one of claims 3 to 8, comprising one or more crimps for connecting the lengths of shape-memory wire to the moveable part, wherein at least one of the stiffening elements and the one or more crimps together form part of a unitary component.
10. An actuator assembly according to claim 8 or 9, wherein the unitary component is formed from a sheet material.
11. An actuator assembly according to any preceding claim, wherein the 20 mechanism comprises one or more features configured to couple the movable part to a removable frame.
12. An actuator assembly according to claim 11, wherein the frame comprises a plurality of arms and each of the features is configured to couple a region of 25 the movable part to one of the arms.
13. An actuator assembly according to claim 12, wherein each of the regions corresponds to a region of relatively high stress in the moveable part when the lengths of wire are selectively powered.
14. An actuator assembly according to claim 13, wherein each of the arms is resilient and each of the features is configured to couple to an arm in such a way that the arm applies a biasing force at the region, wherein the biasing force counteracts the force at the region due to the lengths of wire being selectively powered.
15. An actuator assembly according to claim 14 when dependent on claim 2, wherein the forces at the regions due to the lengths of wire being selectively powered are directed towards and/or away from the axis through the aperture.
16. An actuator assembly according to any preceding claim, wherein the mechanism comprises one or more protrusions on the surface of the movable part within the aperture, the one or more protrusions configured to transfer stress to the auxiliary component.
17. An actuator assembly according to claim 16 when dependent on claim 2, wherein the protrusions are positioned in regions where the forces due to the lengths of wire being selectively powered are directed towards the axis through the aperture.
18. An actuator assembly according to any preceding claim, wherein the mechanism comprises one or more features configured to couple the movable part to the main body via one or more removable wedges, wherein each wedge comprises one or more one or more protrusions for contacting the movable part and/or the main body.
19. An actuator assembly according to claim 18 when dependent on claim 2, wherein the wedges are couplable to regions of the movable part where the forces due to the lengths of wire being selectively powered are directed away from the axis through the aperture.
20. An actuator assembly according to any preceding claim, wherein the movable part is polygonal and at least two apexes of the polygonal movable part have a crimp attached thereto for connecting the lengths of wire to the polygonal moveable part.
21. An actuator assembly according to claim 20 when dependent on claim 15, 17 or 19, wherein: the regions of the movable part where the forces due to the lengths of wire being selectively powered are directed towards the axis through the aperture correspond to the at least two apexes; and/or the regions of the movable part where the forces due to the lengths of wire being selectively powered are directed away from the axis through the aperture correspond to apexes intermediate to the at least two apexes.
22. A camera assembly comprising an actuator assembly according to any one of the preceding claims, wherein the auxiliary component comprises a lens.
23. A kit comprising: an actuator assembly according to claim 12 or any claim dependent thereon; and the removable frame.
24. A kit comprising: an actuator assembly according to claim 18 or any claim dependent thereon; and the removable wedges.
25. A method of attaching an auxiliary component to an actuator assembly according to any one of claims 1 to 21, the method comprising: selectively powering the lengths of wire to position the movable part; and introducing the auxiliary component into the aperture of the moveable part.
26. A method according to claim 25, wherein the actuator assembly is an actuator assembly according to claim 12 or any claim dependent thereon, the method comprising: coupling the frame to the movable part before selectively powering the lengths of wire to position the movable part; and removing the frame after attaching the auxiliary component to the movable part.
27. A method according to claim 25, wherein the actuator assembly is an actuator assembly according to claim 18 or any claim dependent thereon, the method comprising: coupling the movable part to the main body via the one or more wedges before selectively powering the lengths of wire to position the movable part; and removing the wedges after attaching the auxiliary component to the movable part.