Actuator assembly

Abstract

An actuator assembly comprising: a second part that is movable relative to a first part; a first actuating unit configured to apply a first actuating force to the second part that produces a first torque on the second part; and a second actuating unit configured to apply a second actuating force to the second part that produces a second torque on the second part; wherein the first and second torques each have: a torque component in the same sense about the first primary axis; and a torque component in opposite senses about the first secondary axis.

Description

[0001] Actuator assembly

[0002] Field of the disclosure

[0003] The disclosure relates to the field of actuator assemblies.

[0004] Background

[0005] It is known that SMA (shape memory alloy) actuator assemblies may be used in a variety of applications for moving a movable part relative to a support structure. For example, WO 2010 / 029316 A1 describes SMA actuator wires used to provide OIS in a camera by tilting a camera module. WO 2011 / 104518 A1 describes an actuator assembly having eight SMA wires capable of effecting positional control of a movable element with multiple degrees of freedom. It is known to use eight SMA elements to provide rotation or tilt of a movable part. It is an object of the present invention to provide tilt of a movable part using actuator units, using less power than known actuator assemblies.

[0006] Summary of the disclosure

[0007] Against this background, according to a first aspect of the disclosure there is provided an actuator assembly comprising a first part, wherein a primary axis (herein also referred to as a ‘first primary axis’) and a secondary axis (herein also referred to as a ‘first secondary axis’) are defined relative to the first part, the primary axis being perpendicular to the secondary axis. The actuator assembly further comprises a second part that is movable relative to the first part. The actuator assembly further comprises a first actuating unit comprising a first SMA (shape memory alloy) element and configured to apply a first actuating force to the second part that produces a first torque on the second part. The actuator assembly further comprises a second actuating unit comprising a second SMA element and configured to apply a second actuating force to the second part that produces a second torque on the second part. The first and second torques each have a torque component in the same sense about the primary axis; and a torque component in opposite senses about the secondary axis. The actuator assembly further comprises a bearing arrangement comprising a bearing element and configured to engage the second part so as to prevent rotation of the second part about the primary axis, such that on actuation of the first actuating unit and / or the second actuating unit the second part tilts relative to the first part about the secondary axis. In this way, rotation of the second part about the primary axis is constrained and actuation of tilt of the second part about a secondary axis is enabled, using only two actuating units. The first and second actuating units may be used to achieve the tilt about the secondary axis even if the first and second actuating forces applied by the first and second actuating units are in a plane parallel to the secondary axis, allowing a compact arrangement of actuating units relative to the first and second parts. This arrangement uses fewer actuating units to achieve tilt about a secondary axis than would conventionally be used, reducing power consumption and cost of the actuator assembly.

[0008] The first actuating force may be applied to the second part at a first point and the second actuating force may be applied to the second part at a second point, wherein the first point is offset from the secondary axis and the second point is offset from the secondary axis.

[0009] In this way a torque can be produced by the first and second actuating forces about the secondary axis. As will be appreciated, each actuating force can be represented by a point force acting at the relevant point.

[0010] The first actuating force may be applied to the second part at a first point and the second actuating force may be applied to the second part at a second point, wherein the first point and second point are in a first plane perpendicular to the primary axis.

[0011] The first plane may be parallel to and offset from the secondary axis.

[0012] The first actuating force may be applied to the second part at a first point and the second actuating force may be applied to the second part at a second point, wherein the first and second points are offset from the secondary axis and offset from each other along the primary axis.

[0013] In this way, each of the first and second actuating forces produce a torque component in opposite senses about the secondary axis.

[0014] One or both of the first and second actuating forces may be inclined at a non-zero acute angle relative to a plane perpendicular to the primary axis.

[0015] Each of the first and second actuating forces may be inclined at the same angle relative to this plane. The actuator assembly may comprise four sides arranged in a loop around the primary axis, wherein the first actuating force extends along a first side and the second actuating unit extends along a second side that is opposite to the first side.

[0016] The secondary axis may pass through the first and second sides.

[0017] Each of the first and second sides may be perpendicular to the secondary axis and perpendicular to the primary axis.

[0018] The secondary axis may pass between the first and second sides.

[0019] Each of the first and second sides may be parallel to the secondary axis.

[0020] The first and second actuating forces may be parallel to the respective first and second sides. The first actuating force may be inclined at a non-zero angle relative to the first side, and / or the second actuating force may be inclined at a non-zero angle relative to the second side, wherein the angle may be, for example, less than 30 degrees.

[0021] The first actuating force may be applied to the second part at a first point and the second actuating force may be applied to the second part at a second point opposite to the first point with respect to the primary axis.

[0022] The first actuating unit and the second actuating unit may each be connected between the first part and the second part.

[0023] A further primary axis (herein also referred to as a second primary axis) and a further secondary axis (herein also referred to as a second secondary axis) may be defined relative to the second part, the further secondary axis being perpendicular to the further primary axis, wherein the actuator assembly may further comprise: a third part that is movable relative to the second part; a third actuating unit comprising a third SMA element and configured to apply a third actuating force to the third part that produces a third torque on the third part; and a fourth actuating unit comprising a fourth SMA element and configured to apply a fourth torque to the third part. The third and fourth torques each have a torque component in the same sense about the further primary axis; and a torque component in opposite senses about the further secondary axis. The actuator assembly may further comprise a further bearing arrangement comprising a bearing element configured to engage the third part so as to prevent rotation of the third part about the further primary axis, such that on actuation of the third actuating unit and / or the fourth actuating unit the third part tilts relative to the second part about the further secondary axis.

[0024] In this way, tilt of components of the actuator assembly is achievable about two axes. The third part may be tilted about the secondary axis using motion of the second part and tilted about the further secondary axis using the third and fourth actuating units and the further bearing arrangement. Four actuating units may be used to achieve tilt of the third part about two axes.

[0025] The sense of the torque components of the third and fourth torques about the further primary axis may be opposite to the sense of the torque component about the primary axis of the first and second torques.

[0026] The third actuating force may be applied to the third part at a third point and the fourth actuating force may be applied to the third part at a fourth point, wherein the third point is offset from the further secondary axis and the fourth point is offset from the further secondary axis.

[0027] The third actuating force may be applied to the third part at a third point and the fourth actuating force may be applied to the third part at a fourth point, wherein the third point and fourth point are in a first plane perpendicular to the further primary axis and wherein optionally the first plane is parallel to and offset from the further secondary axis.

[0028] The third actuating force may be applied to the third part at a third point and the fourth actuating force may be applied to the third part at a fourth point, wherein the third and fourth points are offset from the further secondary axis and offset from each other along the further primary axis.

[0029] One or both of the third and fourth actuating forces may be inclined at a non-zero acute angle relative to a plane perpendicular to the further primary axis.

[0030] The actuator assembly may comprise four sides arranged in a loop around the primary axis, and wherein the first actuating force extends along a first side, the second actuating unit extends along a second side that is opposite to the first side, the third actuating force extends along a third side that is between the first side and the second side and the fourth actuating unit extends along a fourth side that is opposite to the third side.

[0031] The further secondary axis may pass through the first and second sides. The further secondary axis may pass between the first and second sides.

[0032] In a central position, the further primary axis may be colinear to the primary axis and wherein the further secondary axis is at an angle to the secondary axis.

[0033] The third actuating unit and the fourth actuating unit may each be connected between the second part and the third part.

[0034] The third actuating unit and the fourth actuating unit may each be connected between the first part and the third part.

[0035] The bearing arrangement may comprise first and second bearing elements, wherein the first and second bearing elements are opposite to one another with respect to the primary axis.

[0036] The secondary axis may pass through the first and second bearing elements.

[0037] The further bearing arrangement may comprise third and fourth bearing elements, wherein the third and fourth bearing elements are opposite to one another with respect to the further primary axis.

[0038] The further secondary axis may pass through the third and fourth bearing elements.

[0039] At least one bearing element may comprise a first bearing portion and a second bearing portion, wherein the first bearing portion and the second portion are respectively comprised in either the first part and the second part; or the second part and the third part. On actuation of one or more actuating units the first bearing portion of the at least one bearing element may be configured to engage with the respective second bearing portion of the bearing element, wherein the first bearing portion and / or the second bearing portion of the at least one bearing element is curved.

[0040] One of the first and second bearing portions may be planar.

[0041] On actuation of an actuating unit there may be frictional force between the first bearing portion and the second bearing portion of at least one bearing element, such that the second bearing portion of each of the at least one bearing elements rolls without slipping relative to the respective first bearing portion the bearing element. On actuation of an actuating unit, the second bearing portion of at least one bearing element may rotate relative to the respective first bearing portion of the bearing element, wherein one of the first bearing portion and the second bearing portion of the at least one bearing element may be concave and the other of the first bearing portion and the second bearing portion of the at least one bearing element may be convex, such that the first and second bearing portions the bearing element form curved mating surfaces.

[0042] At least one bearing element may comprises a flexible element connecting the first part to the second part or the third part to the second part, wherein the flexible element is configured to allow rotation of the connected parts relative to one another about the first or second secondary axis.

[0043] The flexible element may comprise a flexure.

[0044] The flexure may be placed in tension by one or more actuating forces.

[0045] The bearing arrangement may be configured to constrain translational movement of the second part relative to the first part. The bearing arrangement may be configured to constrain tilting of the second part relative to the first part about the further secondary axis perpendicular to the further primary axis.

[0046] The first actuating unit may consist of the first SMA element, and / or the second actuating unit may consist of the second SMA element (in which case the references herein to positions and / or directions of actuating forces can equally be taken as references to positions and / or directions of SMA elements).

[0047] Alternatively, at least one of the actuating units may comprise: a body portion; an SMA element connected between the body portion and one of the first and second parts, and configured, on actuation, to apply an input force to the body portion; a force-modifying element connected between the body portion and the one of the first and second parts, and configured to modify the input force so as to give rise to the actuating force; and a coupling link connected between the body portion and the other of the first and second parts, wherein the coupling link is configured to transmit the actuating force from the body portion to the other of the first and second parts, and wherein the coupling link is compliant in a direction perpendicular to the actuating force. Optionally, the first part is movable relative to a fourth part, and the actuator assembly further comprises: a further actuating unit comprising a further SMA element and configured to apply an actuating force that drives relative rotation between the first part relative to the fourth part about a third primary axis defined relative to the fourth part, wherein the third primary axis is non-parallel to the first secondary axis.

[0048] The third primary axis may be at least substantially parallel to the first primary axis.

[0049] Optionally, the bearing arrangement comprises one or more resilient components (for instance flexure components) configured to engage the second part so as to constrain translational movement of the second part relative to the first part in a direction along the first primary axis.

[0050] According to a second aspect of the present disclosure, an apparatus is provided comprising the actuator assembly of the first aspect, wherein the second part and / or the third part comprises an imaging element.

[0051] According to a third aspect of the present disclosure, an apparatus is provided comprising the actuator assembly of the first aspect, wherein the second part and / or the third part comprises one or both of: an image sensor, and a lens assembly. The lens assembly may be configured to focus an image on the image sensor.

[0052] According to a fourth aspect of the present disclosure, an actuator assembly is provided comprising: a first part, wherein a first rotation axis is defined relative to the first part; a second part movable relative to the first part, wherein a second rotation axis is defined relative to the second part; a third part movable relative the second part, wherein a third rotation axis is defined relative to the third part; a fourth part movable relative to the third part. This actuator assembly further comprises a first, a second, and a third actuator arrangement respectively configured to drive relative rotation between the first and second parts, the second and third parts, and the third and fourth parts, respectively about the first, second, and third rotation axes; wherein the rotation axes are non-parallel to each other; and wherein one or more of the actuator arrangements comprises one or more actuating units each comprising an SMA element configured, on actuation, to apply an actuating force to the first, second, third, or fourth part so as to drive the relative rotation between the first and second parts, the second and third parts, or the third and fourth parts. The rotation axes may be at least generally perpendicular to each other. It will be appreciated that the term ‘perpendicular’ here does not mean that the rotation axes must intersect each other in 3D space, although, of course, they may.

[0053] Optionally, two of the three actuator arrangements (for instance the second and third actuator arrangements) each comprise one or more actuating units configured, on actuation, to cause the relative rotation the two actuator arrangements are configured to drive; and the actuating units of the two actuator arrangements are arranged to substantially extend in a common plane at least when the actuator assembly is in a first configuration. The first configuration may be a configuration without tilting.

[0054] Optionally, the actuating units of the two actuator arrangements each comprise an SMA element; wherein the SMA elements of the two actuator arrangements are configured, on actuation, to cause the relative rotation the two actuator arrangements are configured to drive; and wherein the SMA elements of the two actuator arrangements are arranged to substantially extend in a common plane at least when the actuator assembly is in the first configuration.

[0055] Optionally, the other of the three actuator arrangements (for instance the first actuator arrangement) comprises two or four actuating units configured, on selective actuation, to cause the relative rotation the other actuator arrangement is configured to drive; wherein half of the two or four actuating units is configured to drive relative rotation in a first sense, and the other half of the two or four actuating units is configured to drive relative rotation in a second, opposite sense; and wherein the two or four actuating units are arranged to substantially extend in a common plane.

[0056] Optionally, the two or four actuating units each comprise an SMA element; wherein the SMA elements of the two or four actuating units are configured, on selective actuation, to cause the relative rotation the other actuator arrangement is configured to drive; and wherein the SMA elements of the two or four actuating units are arranged to substantially extend in a common plane.

[0057] Optionally, the common plane the two actuator arrangements are arranged to substantially extend in is substantially parallel to the common plane the two or four actuating units are arranged to substantially extend in.

[0058] Optionally, one of the three actuator arrangements (for instance the second actuator arrangement) comprises a first actuating unit comprising a first SMA element and configured to apply a first actuating force to one of the first, second, third, and fourth parts (for instance the third part) that produces a first torque thereon; the one of the three actuator arrangements (for instance the second actuator arrangement) comprises a second actuating unit comprising a second SMA element and configured to apply a second actuating force to the one of the first, second, third, and fourth parts that produces a second torque thereon; wherein the first and second torques each have: a torque component in the same sense about a first primary axis, and a torque component in opposite senses about a first secondary axis, wherein the first primary axis and the first secondary axis are perpendicular to each other and are defined relative to another of the first, second, third, and fourth parts (for instance the second part); wherein the actuator assembly further comprises a bearing arrangement comprising a bearing element and configured to engage the another part (for instance the second part) so as to prevent rotation of the one of the first, second, third, and fourth parts (for instance the third part) about the first primary axis, such that on actuation of the first actuating unit and / or the second actuating unit the one of the first, second, third, and fourth parts (for instance the third part) tilts relative to the another part about the first secondary axis.

[0059] Optionally, another of the three actuator arrangements (for instance the third actuator arrangement) comprises a third actuating unit comprising a third SMA element and configured to apply a third actuating force to a further one of the first, second, third, and fourth parts (for instance the fourth part) that produces a third torque thereon; the another of the three actuator arrangements (for instance the third actuator arrangement) comprises a fourth actuating unit comprising a fourth SMA element and configured to apply a fourth actuating force to the further one of the first, second, third, and fourth parts that produces a fourth torque thereon; wherein the third and fourth torques each have: a torque component in the same sense about a second primary axis, and a torque component in opposite senses about a second secondary axis, wherein the second primary axis and the second secondary axis are perpendicular to each other and are defined relative to a further another of the first, second, third, and fourth parts (for instance the third part, which may also be “the one of the first, second, third, and fourth parts” mentioned in the paragraph above); wherein the actuator assembly further comprises a further bearing arrangement comprising a bearing element and configured to engage the further another part (for instance the third part) so as to prevent rotation of the further one of the first, second, third, and fourth parts (for instance the fourth part) about the second primary axis, such that on actuation of the third actuating unit and / or the fourth actuating unit the further one of the first, second, third, and fourth parts (for instance the fourth part) tilts relative to the further another part about the second secondary axis. Optionally, the last one of the three actuator arrangements (for instance the first actuator arrangement) comprises a fifth and, optionally, a sixth actuating unit respectively comprising a fifth and a sixth SMA element and respectively configured to apply a fifth and a sixth actuating force to an alternative one of the first, second, third, and fourth parts (for instance the second part, which may also be “the another of the first, second, third, and fourth parts” mentioned above) that respectively produces a fifth and a sixth torque thereon; the last one of the three actuator arrangements (for instance the first actuator arrangement) comprises a seventh and, optionally, an eighth actuating unit respectively comprising a seventh and an eighth SMA element and respectively configured to apply a seventh and an eighth actuating force to the alternative one of the first, second, third, and fourth parts (for instance the second part) that respectively produces a seventh and an eighth torque thereon; wherein the fifth and sixth torques each have a torque component in a first sense about a third primary axis, and the seventh and eight torques each have a torque component in a second sense about the third primary axis, wherein the third primary axis is defined relative to an alternative another of the first, second, third, and fourth parts (for instance the first part); and wherein the fifth, sixth, seventh, and eight actuating units are arranged such that, on selective actuation of the fifth, sixth, seventh, and eight actuating units, the alternative one of the first, second, third, and fourth parts (for instance the second part) rotates relative to the alternative another part about the third primary axis.

[0060] Wherein the last one of the three actuator arrangements does not comprise the sixth and eight actuating units, the above-mentioned seventh actuating unit, seventh SMA element, seventh actuating force, and seventh torque may instead be referred to as the sixth actuating unit, sixth SMA element, sixth actuating force, and sixth torque, respectively.

[0061] Optionally, the first secondary axis, the second secondary axis, and the third primary axis may each correspond to each one of the first, second, and third rotation axes.

[0062] Brief description of the drawings

[0063] Specific embodiments of the disclosure will now be described, by way of example only, with reference to the accompanying drawings in which:

[0064] Figure 1 shows a schematic diagram of a plan view of components of an actuator assembly according to an embodiment of the present disclosure having two actuating units;

[0065] Figure 2 shows a schematic diagram of a plan view of an actuator assembly according to an embodiment of the present disclosure having two actuating units; Figure 3 shows a schematic diagram of a side view of the actuator assembly of Figure 2;

[0066] Figure 4 shows a schematic diagram of a perspective view of the actuator assembly of Figure 2;

[0067] Figure 5 shows a schematic diagram of an exploded view of the actuator assembly of Figure 2;

[0068] Figure 6 shows a schematic diagram of a side view of a bearing arrangement of an actuator assembly according to an embodiment of the present disclosure;

[0069] Figure 7 shows a schematic diagram of a perspective view of a bearing arrangement of an actuator assembly according to an embodiment of the present disclosure;

[0070] Figure 7A shows a schematic diagram of a perspective view of a bearing arrangement of an actuator assembly according to an embodiment of the present disclosure;

[0071] Figure 8 shows a schematic diagram of a plan view of an actuator assembly according to an embodiment of the present disclosure having four actuating units;

[0072] Figure 9 shows a schematic diagram of a side view of the actuator assembly of Figure 8;

[0073] Figure 10 shows a schematic diagram of a perspective view of the actuator assembly of Figure 8;

[0074] Figure 11 shows a schematic diagram of an exploded view of the actuator assembly of Figure 8;

[0075] Figure 12 shows a schematic diagram of a perspective view of a bearing arrangement of an actuator assembly according to an embodiment of the present disclosure having two actuating units;

[0076] Figure 13 shows a schematic cross-sectional view of an actuator assembly; and

[0077] Figure 14 shows a schematic plan view of an arrangement of four actuating units.

[0078] Detailed description Figure 1 is a schematic plan view of an actuator assembly 100. The actuator assembly 100 comprises a first part (not shown) and a second part 110. The second part 110 is movable relative to the first part. A primary axis 140 (herein also referred to as a first primary axis) and a secondary axis 150 (herein also referred to as a first secondary axis) are defined relative to the first part, the primary axis 140 being perpendicular to the secondary axis 150. The actuator assembly 100 further comprises a first actuating unit 120 and a second actuating unit 130. The first actuating unit 120 comprises a first SMA (shape memory alloy) element 120. The first actuating unit 120 is configured to apply a first actuating force 123 to the second part 110 that produces a first torque on the second part 110. The second actuating unit 130 comprises a second SMA element 130. The second actuating unit 130 is configured to apply a second actuating force 133 to the second part 110 that produces a second torque on the second part 110. The first and second torques each have a torque component in the same sense 141 about the primary axis 140, and a torque component in opposite senses about the secondary axis 150. The actuator assembly 100 further comprises a bearing arrangement comprising a bearing element and configured to engage the second part 110 so as to prevent rotation of the second part 110 about the primary axis 140, such that on actuation of the first actuating unit 120 and / or the second actuating unit 130 the second part 110 tilts relative to the first part about the secondary axis 150.

[0079] On actuation of the first actuating unit 120, the first actuating force 123 is applied to the second part 110. On actuation of the second actuating unit 130, the second actuating force 133 is applied to the second part 110. The first actuating force 123 produces a first torque on the second part 110. The second actuating force 133 produces a second torque on the second part 110. The first torque and the second torque each have a torque component about the primary axis 140. In the absence of the bearing arrangement, the torque component about the primary axis 140 may result in rotation of the second part 110 relative to the first part about the primary axis 140. However, the bearing arrangement is configured to engage the second part 110 so as to prevent rotation of the second part 110 about the primary axis 140, so the torque component about the primary axis 140 may result in the second part 110 bearing against one or more portions of the bearing arrangement such that rotation of the second part 110 about the primary axis 140 is prevented and the second part 110 instead tilts relative to the first part about the secondary axis 150.

[0080] The actuator assembly 100 comprises four sides arranged in a loop around the primary axis 140. The first actuating force 123 extends along a first side. The first actuating force 123 has a component extending along the first side. The second actuating force 133 extends along a second side that is opposite to the first side. The second actuating force 133 has a component extending along the second side. The secondary axis 150 passes through the first and second sides. Each of the first and second sides are perpendicular to the secondary axis 150. The first and second actuating forces 123, 133 are at least substantially parallel to the respective first and second sides. The first actuating force 123 may be inclined at a non-zero angle relative to the first side, wherein the angle may be, for example, less than 30 degrees. The second actuating force 133 may be inclined at a nonzero angle relative to the second side, wherein the angle may be, for example, less than 30 degrees.

[0081] The first actuating force 123 is applied to the second part 110 at a first point, and the second actuating force 133 is applied to the second part 110 at a second point. As will be appreciated, each actuating force 123, 133 can be represented by a point force acting at the relevant point. The first point is offset from the secondary axis 150 and the second point is offset from the secondary axis 150, such that torque can be produced by the first and second actuating forces 123, 133 about the secondary axis 150. The first and second points are offset from the secondary axis 150 in the same direction (which may be along the primary axis 140). The second point may be opposite to the first point with respect to the primary axis 140.

[0082] The first and second points are in a first plane perpendicular to the primary axis 140. The first and second actuating units 120, 130 are each connected to the second part 110 such that on actuation, the first and second actuating forces 123, 133 each produce a torque component about the primary axis 140 in the same sense 141. The first and second actuating units 120, 130 are directly connected to the second part 110 in this example, but it will be appreciated that the first and second actuating units 120, 130 may instead be indirectly connected to the second part 110 via other components. The first and second actuating forces 123, 133 have force components that act in opposite directions and that are offset from the primary axis 140 in opposite directions.

[0083] The first and second actuating forces 123, 133 are in the first plane perpendicular to the primary axis 140. The first plane is parallel to and offset from the secondary axis 150. The first and second actuating forces 123, 133 act in parallel but opposite directions. The first and second actuating units 120, 130 are connected to opposite corners of the second part 110 such that the first and second actuating forces 123, 133 act on the opposite corners of the second part 110. The first and second actuating units 120, 130 are directly connected to the opposite corners of the second part 110 in this example, but it will be appreciated that the first and second actuating units 120, 130 may instead be indirectly connected to the opposite corners of the second part 110 via other components. One or both of the first and second actuating forces 123, 133 may be inclined at a non-zero acute angle relative to a plane perpendicular to the primary axis 140. Each of the first and second actuating forces 123, 133 may be inclined at the same angle relative to that plane. Each of the first and second actuating forces 123, 133 may be inclined at equal and opposite angles relative to that plane. Each of the first and second actuating forces 123, 133 may be inclined at different angles relative to that plane.

[0084] A first end of the first SMA element 120 is connected to a first corner of the second part 110 at 121 , for instance via a crimp. A second end of the first SMA element 120 is connected to the first part via connection 122 (which may for instance be a crimp). Connection 122 may be a static connection, such that on actuation of the first SMA element 120 the connection 122 does not move relative to the first part. A first end of the second SMA element 130 is connected to a second corner of the second part 110 at 131 , for instance via a crimp, wherein the second corner is opposite to the first corner. A second end of the second SMA element 130 is connected to the first part via connection 132 (which may for instance be a crimp). Connection 132 may be a static connection, such that on actuation of the second SMA element 130 the connection 132 does not move relative to the first part.

[0085] On actuation of the first SMA element 120, the first actuating force 123 is applied to the corner of the second part via 121. On actuation of the second SMA element 130, the second actuating force 133 is applied to the opposing corner of the second part via 131. The first and second actuating forces 123 and 133 result in torque components of the first and second torques, respectively, about the primary axis 140 (out of the page) in the sense indicated by the arrow 141.

[0086] The bearing arrangement comprises a first bearing element (or a first bearing) and a second bearing element (or a second bearing). The first bearing element comprises a first bearing portion 161 and a second bearing portion 162. The second bearing element comprises a first bearing portion 163 and a second bearing portion 164. The first part comprises the first bearing portions 161, 163 of the first and second bearing elements. The second part 110 comprises the second portions 162 and 164 of the first and second bearing elements respectively. The second portion 162, 164 of each bearing element bears against the respective first portion 162, 163 of each bearing element, thereby preventing rotation of the second part 110 about the primary axis 140 relative to the first part. The bearing arrangement is configured such that the second part 110 tilts about the secondary axis 150. The first and second torques each have a torque component in opposite senses about the secondary axis 150, so the sense of the tilt about the secondary axis 150 depends on the comparative magnitudes of the torque component of the first and second torques about the secondary axis 150.

[0087] This is an exemplary arrangement, and the second part 110 and first and second SMA elements 120, 130 may differ from those shown. For example, the second part 110 may vary in shape, and the SMA elements 120, 130 may differ in arrangement relative to one another and relative to the second part 110. For example, the first SMA element 120 may not be parallel to the second SMA element 130.

[0088] The first and second actuating units 120, 130 shown in Figure 1 each comprise an SMA element 120, 130 that is parallel to the first and second actuating forces 123, 133, respectively. However, the actuating units 120, 130 may comprise a different arrangement, wherein the SMA elements 120, 130 of each of the first and second actuating units 120, 130 are not parallel to the respective first and second actuating forces 123, 133. The first and second actuating units 120, 130 may each comprise an SMA element that is in a plane parallel to the first and second actuating forces 123, 133, respectively. The first and second actuating units 120, 130 may each comprise an SMA element that is not in a plane parallel to the first and second actuating forces, respectively.

[0089] Figures 2 to 5 illustrate an actuator assembly 200. The actuator assembly 200 is a specific example of the actuator assembly 100 of Figure 1.

[0090] The bearing arrangement of actuator assembly 200 comprises a first bearing element and a second bearing element. The first and second bearing elements are opposed to one another with respect to the primary axis 270. The first and second bearing elements each comprise a first bearing portion 261 , 264 configured to apply respective first and second bearing forces to the second part 210. The first part 240 comprises the first bearing portion 261 , 264 of each of the first and second bearing elements. The first and second bearing elements each comprise a second bearing portion 262, 263. The second part 210 comprises the second bearing portion 262, 263 of each of the first and second bearing elements. The first bearing portion 261, 264 of each of the first and second bearing elements are configured to apply the first and second bearing forces to the second bearing portion 262, 263 of each of the first and second bearing elements, respectively. On actuation of the first actuating unit (comprising the first SMA element 220) and / or the second actuating unit (comprising the second SMA element 230), the first bearing portions 261 , 264 engage with the respective second bearing portions 262, 263, such that the first bearing portions 261, 264 apply the first and second bearing forces to the second bearing portions 262, 263.

[0091] On actuation of the first actuating unit and / or the second actuating unit, the second bearing portions 262, 263 rotate relative to the respective first bearing portions 261 , 264 such that the second part 210 tilts relative to the first part 240 about the secondary axis 230.

[0092] The second bearing portions 262, 263 are curved, and the first bearing portions 261 , 264 are flat. However, it will be appreciated that alternatively, for each of the first and second bearing elements, one of the first bearing portion 261 , 264 and the second bearing portion 262, 263 may be concave and the other of the first bearing portion 261 , 264 and the second bearing portion 262, 263 may be convex, such that the first and second bearing portions form curved mating surfaces. For example, the second bearing portions 262, 263 may be cylindrical and the first bearing portions 261, 264 may comprise a cylindrical aperture, wherein the second bearing portions are configured to pass into or through the cylindrical apertures. In another example, the second bearing portions 262, 263 may be convex and the first bearing portions 261 , 264 may comprise a concave recess.

[0093] As mentioned above in relation to Figure 1, a first end of the first SMA element 220 is connected to a first corner of the second part 210 at 221 , for instance via a crimp; and a second end of the first SMA element 220 is connected to the first part 240 at 222, for instance via a crimp. Also, as mentioned above in relation to Figure 1 , a first end of the second SMA element 230 is connected to a second corner of the second part 210 at 231 , for instance via a crimp, wherein the second corner is opposite to the first corner; and a second end of the second SMA element 230 is connected to the first part 240 at 232, for instance via a crimp.

[0094] Figure 3 shows a side view of the actuator assembly 200 illustrated in Figure 2. The side view is along A-A as shown in Figure 2. The first bearing element comprises the second bearing portion 262, that is curved in shape. On actuation of the second SMA element 230 (and / or the first SMA element 220), the curved second bearing portion 262 bears against the first bearing portion 261. The curved second bearing portion 262 is configured to rotate with respect to the first bearing portion 261 of the first part 240, allowing the second part 210 to tilt with respect to the first part 240 about the secondary axis 280.

[0095] The second bearing element comprises the second bearing portion 263, that is curved in shape. On actuation of the first SMA element 220 (and / or the second SMA element 230), the curved second bearing portion 263 bears against the first bearing portion 264. The curved second bearing portion 263 is configured to rotate with respect to the first bearing portion 264 of the first part 240, allowing the second part 210 to tilt with respect to the first part 240 about the secondary axis 280.

[0096] The first and second actuating forces 223 and 233 are in the first plane. The first and second SMA elements 220, 230 are in the first plane. The secondary axis 280 about which the second part 210 is able to tilt is in a plane that intersects with the second bearing portion 262 and is offset from and parallel to the first plane.

[0097] At least one of the first bearing portions 261, 264 is provided with a lip configured to restrain translation of the second part 210 relative to the first part 240 parallel to the primary axis 270.

[0098] Figure 4 shows a perspective view of the actuator assembly 200 illustrated in Figures 2 and 3. Figure 5 shows an exploded view of the actuator assembly 200 illustrated in Figures 2, 3 and 4.

[0099] Figure 6 shows an alternative bearing element which may, for example, replace at least one of the first and second bearing elements of the above-mentioned actuator assembly 200. The bearing element comprises a curved second bearing portion 632 of the second part 610 and a first bearing portion 631 of the first part 620. On actuation of the first SMA element and / or the second SMA element, an actuating force 611 is applied such that the second bearing portion 632 bears against the first bearing portion 631 of the first part 620 and the curved second bearing portion 632 rolls against the first bearing portion 631. On actuation of the first actuating unit and / or the second actuating unit, there is a frictional force between the first bearing portion 631 and the second bearing portion 632, such that the second bearing portion 632 rolls without slipping relative to the first bearing portion 631. In other words, there is friction at the contact point between the second bearing portion 632 and the first bearing portion 631 , such that the second bearing portion 632 rolls without slipping with respect to the first bearing portion 631 of the first part 620, allowing the second part 610 to tilt with respect to the first part 620. The second bearing portion 632 is curved and the first bearing portion 631 is flat but may also be curved. The first bearing portion 631 comprises a lip configured to restrain translation of the second part 610 relative to the first part 620 parallel to the primary axis, and / or limit the angle of tilt of the second part 610 about the secondary axis relative to the first part 620.

[0100] Figure 7 shows an alternative bearing element which may, for example, replace at least one of the first and second bearing elements of the above-mentioned actuator assemblies 100, 200. The bearing element comprises a flexible element 730. the second part 710 is connected to the first part 720 via the flexible element 730. The flexible element 730 comprises a flexure 730. On actuation of the first and / or second actuating units, the flexible element 730 and / or the flexure 730 is placed under tension by the first and / or second actuating forces. On actuation of the first SMA element and / or the second SMA element, the flexible element 730 prevents rotation of the second part 710 relative to the first part 720 about the primary axis (for instance buckling of the flexible element 730 may be resisted) but allows, by bending of the flexible element 730 in a direction parallel to the primary axis and perpendicular to the secondary axis, the second part 710 to tilt (for instance rotate) relative to the first part 720 about the secondary axis.

[0101] Alternatively, at least one of the first and second bearing elements of the above-described actuator assemblies 100, 200, may be configured as shown in Figure 7A. The bearing element of Figure 7A comprises a curved second bearing portion 1062 which forms part of the second part 1010, and a first bearing portion 1061 which forms part of the first part 1040. On actuation of the first SMA element and / or the second SMA element, an actuating force is applied such that the second bearing portion 1062 bears against the first bearing portion 1061 . The second bearing portion 1062 is curved and the first bearing portion 1061 is flat but may also be curved. The first bearing portion 1061 comprises a resilient component 1063 (for instance a flexure component 1063) configured to engage the second bearing portion 1062 of the second part so as to constrain translational movement of the second part relative to the first part in a direction along the primary axis (that is parallel to the primary axis), and limit the angle of tilt of the second part about the secondary axis relative to the first part.

[0102] The actuator assemblies 100, 200 described above may further comprise a third part that is tiltable relative to the second part, and the first part, about a further secondary axis (herein also referred to as the second secondary axis) defined relative to the second part, wherein the further secondary axis is: (i) perpendicular to a further primary axis (herein also referred to as a second primary axis) also defined relative to the second part, and (ii) non-parallel to the secondary axis (that is the first secondary axis defined relative to the first part). Where this is the case, the actuator assembly further comprises a third actuating unit and a fourth actuating unit. The third actuating unit comprises a third SMA element and is configured to apply a third actuating force to the third part that produces a third torque on the third part. The fourth actuating unit comprises a fourth SMA element and is configured to apply a fourth actuating force to the fourth part that produces a fourth torque on the third part. The third and fourth torques each have a torque component in the same sense about the further primary axis. The third and fourth torques each have a torque component in opposite senses about the further secondary axis. Moreover, the actuator assembly further comprises a further bearing arrangement comprising at least one bearing element configured to engage the third part so as to prevent rotation of the third part relative to the second part about the further primary axis, and configured such that on actuation of the third actuating unit and / or the fourth actuating unit the third part tilts relative to the second part, and relative to the first part, about the further secondary axis.

[0103] When the actuator assembly is in a configuration without tilting, the further primary axis is colinear, or at least parallel, to the primary axis. The further secondary axis is at an angle to the secondary axis. The further secondary axis may be perpendicular to the secondary axis. The actuator assembly may be biased to the configuration without tilting, such that in an event that no actuating forces are applied to the second and third parts, the actuator assembly is held in the configuration without tilting.

[0104] The sense of the torque components of the third and fourth torques about the further primary axis may be the same as the sense of the torque components about the primary axis of the first and second torques.

[0105] The second part and the third part are arranged such that in an event that the second part is tilted relative to the first part about the secondary axis, the third part is also tilted relative to the first part about the secondary axis along with the second part. In other words, the third part rests on the second part such that the third part is guided by the movement of the second part.

[0106] The third actuating unit and the fourth actuating unit may each be connected between the second part and the third part. Otherwise, the third actuating unit and the fourth actuating unit may each be connected between the first part and the third part.

[0107] The further bearing arrangement comprises third and fourth bearing elements, wherein the third and fourth bearing elements are opposite to one another with respect to the further primary axis. The third and fourth bearing elements may be arranged between the second and third parts in a manner that is similar or identical to the way in which the first and second bearing elements may be arranged between the first and second parts.

[0108] The third and fourth actuating units are arranged between the second and third parts in a manner that is similar or identical to the way in which the first and second actuating units are arranged between the first and second parts. Figures 8 to 11 illustrate an actuator assembly 800. The actuator assembly 800 is a specific example of an actuator assembly which is identical to the actuator assembly 200 but which further comprises the above-described third part, the above-described third and fourth actuating units, and the above-described further bearing arrangement.

[0109] The actuator assembly 800 comprises a first part 840 and a second part 810. These are identical to the first and second parts 210, 240 of the actuator assembly 200. The second part 810 is movable with respect to the first part 840. The actuator assembly 800 further comprises a third part 890 (corresponding to the third part described above) that is movable with respect to the second part 810 and the first part 890. The actuator assembly 800 further comprises a first actuating unit comprising a first SMA element 820 and configured to apply a first actuating force 823 to the second part 840 that produces a torque on the second part 840. The actuator assembly further comprises a second actuating unit comprising a second SMA element 830 and configured to apply a second actuating force 833 on the second part 840 that produces a second torque on the second part 840. The first and second actuating units of actuator assembly 800 are identical to the first and second actuating units of actuator assembly 200. The actuator assembly 800 further comprises a third actuating unit (corresponding to the third actuating unit described above) comprising a third SMA element 825 and configured to apply a third actuating force 828 on the third part 890 that produces a third torque on the third part 890. The actuator assembly 800 further comprises a fourth actuating unit (corresponding to the fourth actuating unit described above) comprising a fourth SMA element 835 and configured to apply a fourth actuating force 838 on the third part 890 that produces a fourth torque on the third part 890.

[0110] Figure 8 shows a plan view of the actuator assembly 800. The primary axis 870 (corresponding to the primary axis 270) is out of the page, and the secondary axis 880 (corresponding to the secondary axis 280) is perpendicular to the primary axis 870. A further secondary axis 885 is perpendicular to the secondary axis 880 and the primary axis 870. The further primary axis is aligned with the primary axis 870 in Figures 8 to 11.

[0111] A first end of the first SMA element 820 is connected to a first corner of the second part 810 at 821 , for instance via a crimp. A second end of the first SMA element 820 is connected to the first part 840 at 822, for instance via a crimp. A first end of the second SMA element 830 is connected to a second corner of the second part 810 at 831 , for instance via a crimp, wherein the second corner is opposite to the first corner. A second end of the second SMA element 830 is connected to the first part 840 at 832, for instance via a crimp. On actuation of the first SMA element 820, the first actuating force 823 is applied to the corner of the second part via 821. On actuation of the second SMA element 830, a second actuating force 833 is applied to the opposing corner of the second part via 831. The first and second actuating forces 823, 833 result in torque components of the first and second torques, respectively, about the primary axis 870 in the same sense. A bearing arrangement (identical to the bearing arrangement of actuator assembly 200) comprises a first bearing element comprising first bearing portion 861 and a second bearing portion 862. The bearing arrangement comprises a second bearing element comprising first bearing portion 863 and a second bearing portion 864. The first part 840 comprises the first bearing portions 861 , 863 and the second part 810 comprises the second bearing portions 862, 864. The bearing arrangement is configured such that the second part 810 tilts relative to the first part 840 about the secondary axis 880.

[0112] A first end of the third SMA element 825 is connected to a first corner of the third part 890 at 827, for instance via a crimp. A second end of the third SMA element 825 is connected to the second part 810 at 826. A first end of the fourth SMA element 835 is connected to a second corner of the third part 890 at 837, wherein the second corner is opposite to the first corner. A second end of the fourth SMA element 835 is connected to the second part 810 at 836.

[0113] On actuation of the third SMA element 825, a third actuating force 828 is applied to the corner of the third part 890 via 827. On actuation of the fourth SMA element 835, a fourth actuating force 838 is applied to the opposing corner of the third part 890 via 837. The third and fourth actuating forces 828, 838 result in torque components of the third and fourth torques, respectively, about the further primary axis in the same sense. The further bearing arrangement comprises a third bearing element and a fourth bearing element. The third bearing element comprises a first bearing portion 866 and a second bearing portion 867. The fourth bearing element comprises a first bearing portion 868 and a second bearing portion 869. The second part 810 comprises the first bearing portions 866 and 868 of the third and fourth bearing elements, and the third part 890 comprises the second bearing portions 867 and 869 of the third and fourth bearing elements. Portions 867 and 869 are not visible in Figure 8 (see Figures 9 to 11). The further bearing arrangement is configured such that the third part 890 tilts relative to the second part 810, and the first part 840, about the further secondary axis 885.

[0114] Figure 9 shows a side view of the actuator assembly 800 illustrated in Figure 8. The side view is along B-B as shown in Figure 8. The second bearing portions 862, 864 are curved in shape. On actuation of the second SMA element 830 (and / or the first SMA element 820), the curved second bearing portions 862, 864 bear against the first bearing portions 861 , 863 of the first part 840. The curved second bearing portions 862, 864 are configured to rotate with respect to the first bearing portions 861 , 863 of the first part 840, allowing the second part 810 to tilt with respect to the first part 840 about the secondary axis 880.

[0115] Similarly, the second bearing portions 867, 869 are curved in shape. On actuation of the third SMA element 825 (and / or the fourth SMA element 835), the curved second bearing portions 867, 869 bear against the first bearing portions 866, 868. The curved second bearing portions 867, 869 are configured to rotate with respect to the first bearing portions 866, 868, allowing the third part 890 to tilt with respect to the second part 810 (and the first part 840) about the further secondary axis 885.

[0116] The first and second SMA elements 820 and 830 are in a first plane in this example. The secondary axis 880 about which the second part 810 is able to tilt is in a plane that intersects with the second bearing portions 862 and 864 and is offset from and parallel to the first plane. The third and fourth SMA elements 825, 835 are in a second plane in this example. The further secondary axis 885 about which the third part 890 is able to tilt is in a plane that intersects with the second bearing portion 867 and 869 and is offset from and parallel to the second plane. The first plane in which the first and second SMA elements 820, 830 are in, and the second plane in which the third and fourth SMA elements 825, 835 are in, may be parallel and / or at least substantially co-planar.

[0117] At least one of the first bearing portions 861, 863, 866, 868 is provided with a lip configured to restrain translation of the second part 210 relative to the first part 240 parallel to the primary axis 270.

[0118] Figure 10 shows a perspective view of the actuator assembly 800 illustrated in Figures 8 and 9. Figure 11 shows an exploded view of the actuator assembly 800 illustrated in Figures 8, 9 and 10.

[0119] One or more of the bearing elements of actuator assembly 800 may for instance be replaced with a bearing element similar or identical to that of Figure 6, Figure 7, and / or Figure 7A.

[0120] The actuator assembly 800 illustrated in Figures 8 to 11 comprises a first pair of SMA elements 820, 830 connected between the first part 840 and the second part 810, and then a second pair of SMA elements 825, 835 connected between the second part 810 and the third part 890. The first pair of SMA elements generate actuating forces to rotate the second part 810 (and also the third part 890) about secondary axis 880 relative to the first part 840. The second pair of SMA elements generate actuating forces to rotate the third part 890 about further secondary axis 885 relative to the second part 810 (and also the first part 840). In a variation (which is not shown) each SMA element may be connected at one end to the first part 840 and at a second end to the third part 890. Each SMA element may be arranged in a single plane offset along the primary axis 870 from the secondary axis 880 and the further secondary axis 885. Each SMA element may be arranged so that it generates a torque acting in the same direction about the primary axis 870 so that the bearing portions are loaded as previously described. Rotation about the secondary axis 880 and the further secondary axis 885 is achieved by control of SMA element tension for all four SMA elements. This approach has the advantage of simplifying electrical connections as no electrical connection is required to the second part 810. This simplification may be at the expense of more complex control of the SMA elements to achieve the same rotation about the secondary axis 880 and the further secondary axis 885.

[0121] All of the actuator assemblies discussed above comprise: four sides arranged in a loop around the primary axis, first and second actuating forces extending along a first side and a second side that is opposite to the first side, and the secondary axis passing through the first and second sides. However, as shown in Figure 12, alternatively, the secondary axis (that is axis 952 in Figure 12) may pass between the first and second sides (that is the sides the first and second SMA elements 920 and 930 are provided at). Where this is the case, each of the first and second sides may be parallel to the secondary axis 952 and perpendicular to the primary axis 951 .

[0122] As illustrated in Figure 12, the first and second actuating units 920 and 930 may not be in the same plane and may not be parallel to one another. The secondary axis 952 may be between the first and second actuating units 920 and 930. The first and second actuating units 920 and 930 may be in a first plane and second plane, respectively, wherein the first and second planes are parallel to and offset from the primary axis 951. The first and second actuating units 920 and 930 may each exert first and second actuating forces that are inclined at a non-zero acute angle relative to a plane perpendicular to the primary axis 951 . Each of the first and second actuating forces may exert a torque on the second part 910 having a torque component about the primary axis 951 for loading the bearing arrangement and a torque component for driving rotation about the secondary axis 952. In other examples, the first and second actuating forces may be in planes not parallel to the primary axis 951. The embodiment of Figure 12 is extensible to rotation about a further secondary axis (not shown) that is perpendicular to the primary axis 951 and the secondary axis 952 by adding a third part and two further SMA elements serially as described above for the embodiment of figures 8 to 11. In a further extension all four SMA elements may be connected between a first part and a third part (with no connection to an intermediate second part) enabling rotation about the secondary axis and the further secondary axis in parallel. Each SMA element acts to generate a torque in the same direction about the primary axis for loading the bearing arrangements. The angled wire arrangement may also result in the force delta between SMA elements per secondary axis remaining the same, reducing the likelihood of the bearing arrangements translating in an unwanted way.

[0123] As illustrated in Figure 13, the first part 840 of the actuator assembly 800 may be movable relative to a fourth part 10 of the actuator assembly 800. Where this is the case, the actuator assembly 800 further comprises: one or more further actuating units (not shown) each comprising a further SMA element and each configured to apply an actuating force that drives relative rotation between the first part 840 and the fourth part 10 about a third primary axis P defined relative to the fourth part 10, wherein the third primary axis P is nonparallel to the first secondary axis 880 and non-parallel to the second secondary axis 885. The third primary axis P may be at least substantially parallel to the primary axis 870. The third primary axis P may be collinear with the primary axis 870.

[0124] The one or more further actuating units may comprise four actuating units configured to drive the relative rotation between the first part 840 and the fourth part 10 by selectively applying actuating forces F between the first part 840 and the fourth part 10 as illustrated in Figure 14. The arrangement of actuating forces F of Figure 14 corresponds to the arrangement of SMA wires described in WO2013 / 175197 A1 , which is herein incorporated by reference to the maximum extent permissible by law.

[0125] An alternative description for the actuator assembly of Figure 13 is provided below.

[0126] The actuator assembly comprises a first part 10, a second part 840 movable relative to the first part 10, a third part 810 movable relative the second part 840, and a fourth part 890 movable relative to the third part 810. A first rotation axis P is defined relative to the first part 10. A second rotation axis 880 is defined relative to the second part 840. A third rotation axis 885 is defined relative to the third part 810. The actuator assembly further comprises a first, a second, and a third actuator arrangement respectively configured to drive relative rotation between the first and second parts 10, 840, the second and third parts 840, 810, and the third and fourth parts 810, 890, respectively about the first, second, and third rotation axes P, 880, 885. The rotation axes P, 880, 885 are non-parallel to each other. One or more of the actuator arrangements comprises one or more actuating units each comprising an SMA element configured, on actuation, to apply an actuating force to the first, second, third, or fourth parts 10, 840, 810, 890 so as to drive the relative rotation between the first and second parts 10, 840, the second and third parts 840, 810, or the third and fourth parts 810, 890.

[0127] The rotation axes P, 880, 885 may be at least generally perpendicular to each other. It will be appreciated that the term ‘perpendicular’ does not mean that the rotation axes must intersect each other in 3D space, although, of course, they may.

[0128] Two of the three actuator arrangements (that is actuator arrangements that may correspond to the SMA elements 820, 830, 825, 835 of Figure 11) each comprise one or more actuating units configured, on actuation, to cause the relative rotation of the two actuator arrangements; and the actuating units of the two actuator arrangements (that is the SMA elements 820, 830, 825, 835) are arranged to substantially extend in a common plane at least when the actuator assembly is in a configuration without tilting.

[0129] The actuating units of the two actuator arrangements each comprise an SMA element. The SMA elements of the two actuator arrangements (that is the SMA elements 820, 830, 825, 835) are configured, on actuation, to cause the relative rotation the two actuator arrangements. The SMA elements of the two actuator arrangements are arranged to substantially extend in a common plane at least when the actuator assembly is in the first configuration.

[0130] The other of the three actuator arrangements (for instance the first actuator arrangement) comprises two or four actuating units configured, on selective actuation, to cause the relative rotation of the other actuator arrangement. Half of the two or four actuating units are configured to drive relative rotation in a first sense, and the other half of the two or four actuating units are configured to drive relative rotation in a second, opposite sense. The two or four actuating units may be arranged to substantially extend in a common plane.

[0131] The two or four actuating units each comprise an SMA element. The SMA elements of the two or four actuating units are configured, on selective actuation, to cause the relative rotation the other actuator arrangement is configured to drive. The SMA elements of the two or four actuating units are arranged to substantially extend in a common plane. Optionally, the common plane the two actuator arrangements are arranged to substantially extend in is substantially parallel to the common plane the two or four actuating units are arranged to substantially extend in. Optionally, the common plane the SMA elements of the two actuator arrangements are arranged to substantially extend in is substantially parallel to the common plane the SMA elements of the two or four actuating units are arranged to substantially extend in.

[0132] One of the three actuator arrangements (for instance the second actuator arrangement) comprises a first actuating unit comprising a first SMA element (for instance SMA element 820) and configured to apply a first actuating force (for instance force 823) to one of the first, second, third, and fourth parts 10, 840, 810, 890 (for instance the third part 810) that produces a first torque thereon. The one of the three actuator arrangements (for instance the second actuator arrangement) comprises a second actuating unit comprising a second SMA (for instance SMA element 830) element and configured to apply a second actuating force (for instance force 833) to the one of the first, second, third, and fourth parts (for instance the third part 810) that produces a second torque thereon. The first and second torques each have: a torque component in the same sense about a first primary axis (for instance primary axis 870), and a torque component in opposite senses about a first secondary axis (for instance secondary axis 880), wherein the first primary axis and the first secondary axis are perpendicular to each other and are defined relative to another of the first, second, third, and fourth parts (for instance the second part 840). The actuator assembly further comprises a bearing arrangement comprising a bearing element and configured to engage the another part (for instance the second part 840) so as to prevent rotation of the one of the first, second, third, and fourth parts (for instance the third part 810) about the first primary axis, such that on actuation of the first actuating unit and / or the second actuating unit the one of the first, second, third, and fourth parts (for instance the third part 810) tilts relative to the another part (for instance the second part 840) about the first secondary axis.

[0133] Another of the three actuator arrangements (for instance the third actuator arrangement) comprises a third actuating unit comprising a third SMA element (for instance SMA element 825) and configured to apply a third actuating force (for instance force 828) to a further one of the first, second, third, and fourth parts 10, 840, 810, 890 (for instance the fourth part 890) that produces a third torque thereon. The another of the three actuator arrangements (for instance the third actuator arrangement) comprises a fourth actuating unit comprising a fourth SMA element (for instance SMA element 835) and configured to apply a fourth actuating force (for instance force 838) to the further one of the first, second, third, and fourth parts that produces a fourth torque thereon. The third and fourth torques each have: a torque component in the same sense about a second primary axis (for instance further primary axis), and a torque component in opposite senses about a second secondary axis (for instance further secondary axis 885), wherein the second primary axis and the second secondary axis are perpendicular to each other and are defined relative to a further another of the first, second, third, and fourth parts (for instance the third part 810). The actuator assembly further comprises a further bearing arrangement comprising a bearing element and configured to engage the further another part (for instance the third part 810) so as to prevent rotation of the further one of the first, second, third, and fourth parts (for instance the fourth part 890) about the second primary axis, such that on actuation of the third actuating unit and / or the fourth actuating unit the further one of the first, second, third, and fourth parts (for instance the fourth part 890) tilts relative to the further another part (for instance third part 810) about the second secondary axis.

[0134] The last one of the three actuator arrangements (for instance the first actuator arrangement) comprises a fifth and, optionally, a sixth actuating unit respectively comprising a fifth and a sixth SMA element and respectively configured to apply a fifth and a sixth actuating force to an alternative one of the first, second, third, and fourth parts 10, 840, 810, 890 (for instance the second part 840) that respectively produces a fifth and a sixth torque thereon. The last one of the three actuator arrangements (for instance the first actuator arrangement) comprises a seventh and, optionally, an eighth actuating unit respectively comprising a seventh and an eighth SMA element and respectively configured to apply a seventh and an eighth actuating force to the alternative one of the first, second, third, and fourth parts (for instance the second part 840) that respectively produces a seventh and an eighth torque thereon. The fifth and sixth torques each have a torque component in a first sense about a third primary axis (for instance axis P), and the seventh and eight torques each have a torque component in a second (opposite) sense about the third primary axis, wherein the third primary axis is defined relative to an alternative another of the first, second, third, and fourth parts (for instance the first part 10). The fifth, sixth, seventh, and eight actuating units are arranged such that, on selective actuation of the fifth, sixth, seventh, and eight actuating units, the alternative one of the first, second, third, and fourth parts (for instance the second part 840) rotates relative to the alternative another part (for instance the first part 10) about the third primary axis.

[0135] Wherein the last one of the three actuator arrangements does not comprise the sixth and eight actuating units, the above-mentioned seventh actuating unit, seventh SMA element, seventh actuating force, and seventh torque may instead be referred to as the sixth actuating unit, sixth SMA element, sixth actuating force, and sixth torque, respectively. Other variations

[0136] It will be appreciated that there may be many other variations of the above-described examples.

[0137] For example, the actuator assemblies described above may include different types of actuating units to those described above. Examples of such actuating units include a folded SMA wire arrangement as disclosed in WO 2021 / 111131 A1, a V-shaped SMA wire with a compliant connector as disclosed in WO 2013 / 121225 A1 , a scissor jack arrangement as disclosed in WO 2021 / 156458 A1 , a two-stage arrangement as disclosed in WO 2021 / 111181 A1 , or an SMA actuating unit with a force-modifying mechanism as disclosed in WO 2022 / 084699 A1 . The documents referred to in the preceding sentence are each herein incorporated by reference to the maximum extent permissible by law. The actuator assembly may have any number of different types of actuating units and may have any suitable number of actuating units of each type. It will also be appreciated that the actuating units may comprise non-SMA actuating units, for instance voice-coil motor (VCM) actuating units.

[0138] The bearing arrangement may be any arrangement that allows the second part to tilt relative to the first part about the secondary axis. The bearing arrangement may comprise components that, on actuation of the first and / or second actuating units, have high or low friction between them. The bearing arrangement may comprise components that, on actuation of the first and / or second actuating units, bear against one another. The bearing arrangement may comprise components that, on actuation of the first and / or second actuating units, resist relative motion between the components in one direction and permit relative motion between the components in another direction.

[0139] Similarly, the further bearing arrangement may be any arrangement that allows the third part to tilt relative to the second part about the further secondary axis. The further bearing arrangement may comprise components that, on actuation of the third and / or fourth actuating units, have high or low friction between them. The further bearing arrangement may comprise components that, on actuation of the third and / or fourth actuating units, bear against one another. The further bearing arrangement may comprise components that, on actuation of the third and / or fourth actuating units, resist relative motion between the components in one direction and permit relative motion between the components in another direction. A “part” as used herein may be one component or may be more than one component. In an event that a “part” is more than one component, the components may be in an assembly, or attached together, or separate.

[0140] In the foregoing, the sense of a torque has been discussed. This is intended to mean the sense (or direction) of the rotation that arises due to the torque.

[0141] In certain examples, the above-described actuator assemblies may be incorporated in an apparatus such as a camera assembly. The second part and / or the third part of the actuator assembly may comprise an optical element (for instance a lens assembly) and / or an imaging element (for instance image sensor). The lens assembly may be configured to focus an image on the imaging element. The actuator assembly may be configured to provide the tilting about the secondary axis, the tilting about the further secondary axis, and / or the rotating about the third primary axis for providing optical image stabilisation (OIS) functionality. The apparatus may be incorporated in a portable electronic device, such as a smartphone.

[0142] SMA

[0143] The above-described SMA actuator assemblies comprise at least one SMA element. The term ‘shape memory alloy (SMA) element’ may refer to any element comprising SMA. The SMA element may be described as an SMA wire. The SMA element may have any shape that is suitable for the purposes described herein. The SMA element may be elongate and may have a round cross section or any other shape cross section. The cross section may vary along the length of the SMA element. The SMA element might have a relatively complex shape such as a helical spring. It is also possible that the length of the SMA element (however defined) may be similar to one or more of its other dimensions. The SMA element may be sheet-like, and such a sheet may be planar or non-planar. The SMA element may be pliant or, in other words, flexible. In some examples, when connected in a straight line between two components, the SMA element can apply only a tensile force which urges the two components together. In other examples, the SMA element may be bent around a component and can apply a force to the component as the SMA element tends to straighten under tension. The SMA element may be beam-like or rigid and may be able to apply different (for instance non-tensile) forces to elements. The SMA element may or may not include material(s) and / or component(s) that are not SMA. For example, the SMA element may comprise a core of SMA and a coating of non-SMA material. Unless the context requires otherwise, the term ‘SMA element’ may refer to any configuration of SMA material acting as a single actuating element which, for example, can be individually controlled to produce a force on an element. For example, the SMA element may comprise two or more portions of SMA material that are arranged mechanically in parallel and / or in series. In some arrangements, the SMA element may be part of a larger SMA element. Such a larger SMA element might comprise two or more parts that are individually controllable, thereby forming two or more SMA elements. The SMA element may comprise an SMA wire, SMA foil, SMA film or any other configuration of SMA material. The SMA element may be manufactured using any suitable method, for example by a method involving drawing, rolling, deposition, sintering or powder fusion. The SMA element may exhibit any shape memory effect, for instance a thermal shape memory effect or a magnetic shape memory effect, and may be controlled in any suitable way, for instance by Joule heating, another heating technique or by applying a magnetic field.

[0144] In certain embodiments, the actuating units described above may be configured to apply an actuating force in a direction parallel to the SMA element of the actuating unit. In other embodiments, the actuating units described above may be configured to apply an actuating force in a direction at an angle to the SMA element of the actuating unit. The actuating unit may comprise a force-modifying element configured to change the direction and / or magnitude of the force exerted by the SMA element such that the actuating force has a different direction and / or magnitude to the force exerted by the SMA element. In certain examples, the actuating unit may comprise a flexure configured to deform on actuation of the SMA element.

Claims

CLAIMS:

1. An actuator assembly comprising: a first part, wherein a first primary axis and a first secondary axis are defined relative to the first part, the first primary axis being perpendicular to the first secondary axis; a second part that is movable relative to the first part; a first actuating unit comprising a first shape memory alloy, SMA, element and configured to apply a first actuating force to the second part that produces a first torque on the second part; and a second actuating unit comprising a second SMA element and configured to apply a second actuating force to the second part that produces a second torque on the second part; wherein the first and second torques each have: a torque component in the same sense about the first primary axis; and a torque component in opposite senses about the first secondary axis; wherein the actuator assembly further comprises a bearing arrangement comprising a bearing element and configured to engage the second part so as to prevent rotation of the second part about the first primary axis, such that on actuation of the first actuating unit and / or the second actuating unit the second part tilts relative to the first part about the first secondary axis.

2. The actuator assembly of claim 1 , wherein the first actuating force is applied to the second part at a first point and the second actuating force is applied to the second part at a second point, wherein the first point is offset from the first secondary axis and the second point is offset from the first secondary axis.

3. The actuator assembly of claim 1 or 2, wherein the first actuating force is applied to the second part at a first point and the second actuating force is applied to the second part at a second point, wherein the first point and second point are in a first plane perpendicular to the first primary axis; and, optionally, wherein the first plane is parallel to and offset from the first secondary axis.

4. The actuator assembly of claim 1 or 2, wherein one or both of the first and second actuating forces are inclined at a non-zero acute angle relative to a plane perpendicular to the first primary axis.

5. The actuator assembly of any preceding claim, wherein the actuator assembly comprises four sides arranged in a loop around the first primary axis, and wherein the first actuating force extends along a first side and the second actuating unit extends along a second side that is opposite to the first side.

6. The actuator assembly of claim 5, wherein the first secondary axis passes through the first and second sides, or wherein the first secondary axis passes between the first and second sides.

7. The actuator assembly of any preceding claim, wherein the first actuating force is applied to the second part at a first point and the second actuating force is applied to the second part at a second point opposite to the first point with respect to the first primary axis.

8. The actuator assembly of any preceding claim, wherein the first actuating unit and the second actuating unit are each connected between the first part and the second part.

9. The actuator assembly of any preceding claim, wherein a second primary axis and a second secondary axis are defined relative to the second part, the second secondary axis being perpendicular to the second primary axis, wherein the actuator assembly further comprises: a third part that is movable relative to the second part; a third actuating unit comprising a third SMA element and configured to apply a third actuating force to the third part that produces a third torque on the third part; and a fourth actuating unit comprising a fourth SMA element and configured to apply a fourth torque to the third part; wherein the third and fourth torques each have: a torque component in the same sense about the second primary axis; and a torque component in opposite senses about the second secondary axis; and wherein the actuator assembly comprises a further bearing arrangement comprising a bearing element configured to engage the third part so as to prevent rotation of the third part about the second primary axis, such that on actuation of the third actuating unit and / or the fourth actuating unit the third part tilts relative to the second part about the second secondary axis.

10. The actuator assembly of claim 9, wherein the sense of the torque components of the third and fourth torques about the second primary axis is opposite to the sense of the torque component about the first primary axis of the first and second torques.11 . The actuator assembly of claim 9 or 10, wherein the third actuating force is applied to the third part at a third point and the fourth actuating force is applied to the third part at a fourth point, wherein the third point is offset from the second secondary axis and the fourth point is offset from the second secondary axis.

12. The actuator assembly of any of claims 9 to 11, wherein the third actuating force is applied to the third part at a third point and the fourth actuating force is applied to the third part at a fourth point, wherein the third point and fourth point are in a first plane perpendicular to the second primary axis and wherein optionally the first plane is parallel to and offset from the second secondary axis.

13. The actuator assembly of any of claims 9 to 12, wherein one or both of the third and fourth actuating forces are inclined at a non-zero acute angle relative to a plane perpendicular to the second primary axis.

14. The actuator assembly of any of claims 9 to 13, wherein the actuator assembly comprises four sides arranged in a loop around the first primary axis, and wherein the first actuating force extends along a first side, the second actuating unit extends along a second side that is opposite to the first side, the third actuating force extends along a third side that is between the first side and the second side and the fourth actuating unit extends along a fourth side that is opposite to the third side; and, optionally, wherein the second secondary axis passes either: through the first and second sides; or between the first and second sides.

15. The actuator assembly of any of claims 9 to 14, wherein in a central position, the second primary axis is colinear to the first primary axis and wherein the second secondary axis is at an angle to the first secondary axis.

16. The actuator assembly of any of claims 9 to 15, wherein the third actuating unit and the fourth actuating unit are each connected between either: the second part and the third part; or the first part and the third part.

17. The actuator assembly of any preceding claim, wherein at least one bearing element comprises a first bearing portion and a second bearing portion, wherein the first bearing portion and the second portion are respectively comprised in either: the first part and the second part; or the second part and the third part; wherein on actuation of one or more actuating units the first bearing portion of the at least one bearing element is configured to engage with the respective second bearing portion of the bearing element; and wherein the first bearing portion and / or the second bearing portion of the at least one bearing element is curved.

18. The actuator assembly of any of claims 1 to 16, wherein at least one bearing element comprises a flexible element connecting the first part to the second part or the third part to the second part, wherein the flexible element is configured to allow rotation of the connected parts relative to one another about the first or second secondary axis, wherein optionally: the flexible element comprises a flexure, wherein optionally the flexure is placed in tension by one or more actuating forces.

19. An actuator assembly according to any preceding claim, wherein the first part is movable relative to a fourth part, and wherein the actuator assembly further comprises: a further actuating unit comprising a further SMA element and configured to apply an actuating force that drives relative rotation between the first part relative to the fourth part about a third primary axis defined relative to the fourth part, wherein the third primary axis is non-parallel to the first secondary axis.

20. An actuator assembly comprising: a first part, wherein a first rotation axis is defined relative to the first part; a second part movable relative to the first part, wherein a second rotation axis is defined relative to the second part; a third part movable relative the second part, wherein a third rotation axis is defined relative to the third part; a fourth part movable relative to the third part; a first, a second, and a third actuator arrangement respectively configured to drive relative rotation between the first and second parts, the second and third parts,and the third and fourth parts, respectively about the first, second, and third rotation axes; wherein the rotation axes are non-parallel to each other; and wherein one or more of the actuator arrangements comprises one or more actuating units each comprising a shape memory alloy, SMA, element configured, on actuation, to apply an actuating force to the first, second, third, or fourth part so as to drive the relative rotation between the first and second parts, the second and third parts, or the third and fourth parts.21 . An actuator assembly according to claim 20, wherein two of the three actuator arrangements each comprise one or more actuating units configured, on actuation, to cause the relative rotation the two actuator arrangements are configured to drive; and wherein the actuating units of the two actuator arrangements are arranged to substantially extend in a common plane at least when the actuator assembly is in a first configuration.

22. An actuator assembly according to claim 21 , wherein the other of the three actuator arrangements comprises two or four actuating units configured, on selective actuation, to cause the relative rotation the other actuator arrangement is configured to drive; wherein half of the two or four actuating units are configured to drive relative rotation in a first sense, and the other half of the two or four actuating units is configured to drive relative rotation in a second, opposite sense; and wherein the two or four actuating units are arranged to substantially extend in a common plane.

23. An actuator assembly according to any of claims 20 to 22, wherein one of the three actuator arrangements comprises: a first actuating unit comprising a first SMA element configured to apply a first actuating force to one of the first, second, third, and fourth parts that produces a first torque thereon; and a second actuating unit comprising a second SMA element configured to apply a second actuating force to the one of the first, second, third, and fourth parts that produces a second torque thereon; wherein the first and second torques each have: a torque component in the same sense about a first primary axis, anda torque component in opposite senses about a first secondary axis, wherein the first primary axis and the first secondary axis are perpendicular to each other and are defined relative to another of the first, second, third, and fourth parts; wherein the actuator assembly further comprises a bearing arrangement comprising a bearing element and configured to engage the another of the first, second, third, and fourth parts so as to prevent rotation of the one of the first, second, third, and fourth parts about the first primary axis, such that on actuation of the first actuating unit and / or the second actuating unit the one of the first, second, third, and fourth parts tilts relative to the another of the first, second, third, and fourth parts about the first secondary axis.

24. An actuator assembly according to claim 23, wherein another of the three actuator arrangements comprises: a third actuating unit comprising a third SMA element configured to apply a third actuating force to a further one of the first, second, third, and fourth parts that produces a third torque thereon; and a fourth actuating unit comprising a fourth SMA element configured to apply a fourth actuating force to the further one of the first, second, third, and fourth parts that produces a fourth torque thereon; wherein the third and fourth torques each have: a torque component in the same sense about a second primary axis, and a torque component in opposite senses about a second secondary axis, wherein the second primary axis and the second secondary axis are perpendicular to each other and are defined relative to a further another of the first, second, third, and fourth parts; wherein the actuator assembly further comprises a further bearing arrangement comprising a bearing element and configured to engage the further another of the first, second, third, and fourth parts so as to prevent rotation of the further one of the first, second, third, and fourth parts about the second primary axis, such that on actuation of the third actuating unit and / or the fourth actuating unit the further one of the first, second, third, and fourth parts tilts relative to the further another of the first, second, third, and fourth parts about the second secondary axis.

25. An actuator assembly according to claim 24, wherein the last one of the three actuator arrangements comprises: a fifth and, optionally, a sixth actuating unit respectively comprising a fifth and a sixth SMA element and respectively configured to apply a fifth and a sixth actuatingforce to an alternative one of the first, second, third, and fourth parts that respectively produces a fifth and a sixth torque thereon; and a seventh and, optionally, an eighth actuating unit respectively comprising a seventh and an eighth SMA element and respectively configured to apply a seventh and an eighth actuating force to the alternative one of the first, second, third, and fourth parts that respectively produces a seventh and an eighth torque thereon; wherein the fifth and sixth torques each have a torque component in a first sense about a third primary axis, and the seventh and eight torques each have a torque component in a second sense about the third primary axis, wherein the third primary axis is defined relative to an alternative another of the first, second, third, and fourth parts; and wherein the fifth, sixth, seventh, and eight actuating units are arranged such that, on selective actuation of the fifth, sixth, seventh, and eight actuating units, the alternative one of the first, second, third, and fourth parts rotates relative to the alternative another of the first, second, third, and fourth parts about the third primary axis.

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