Actuator assembly

Abstract

An actuator assembly having a first axis, the actuator assembly comprising: a first part; a second part that is movable relative to the first part; and one or more actuating units each configured to apply an actuating force capable of moving the second part relative to the first part, wherein at least one of the actuating units comprises: a body portion; an SMA (shape memory alloy) element connected between the body portion and at least 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.

Description

[0001] ACTUATOR ASSEMBLY

[0002] Field

[0003] The present application relates to an actuator assembly with at least one actuating unit including a shape memory alloy (SMA) element.

[0004] Background

[0005] SMA actuator assemblies may be used in a variety of applications for moving a movable part relative to a support structure.

[0006] For example, WO 2013 / 175197 Al describes a camera in which four SMA wires are arranged to move a lens element relative to an image sensor in a plane that is perpendicular to the optical axis of the lens element, thereby effecting optical image stabilization (OIS). WO 2010 / 029316 Al describes SMA wires used to provide OIS in a camera by tilting a camera module. WO 2011 / 104518 Al describes an actuator assembly having eight SMA wires capable of effecting positional control of a movable element with multiple degrees of freedom.

[0007] Typically, the range of movement (also known as "stroke") of such SMA actuator assemblies is limited by the maximum contraction of the SMA wires, and the actuating force is limited by the maximum force that can be generated by the SMA wires. To increase the movement range or the actuating force, longer or thicker SMA wires can be used, but this may be at the expense of increased cost, size and / or power, which may not be practical in miniature applications.

[0008] WO 2022 / 084699 Al discloses an actuator assembly comprising at least one actuating unit (incorporating an SMA wire) that, on actuation, moves a movable part relative to the support structure. The actuating unit may be configured to increase the stroke or the actuating force and / or to re-direct the force applied by the SMA wire.

[0009] Summary

[0010] According to a first aspect of the present invention, there is provided an actuator assembly having a first axis, the actuator assembly comprising: a first part; a second part that is movable relative to the first part; and one or more actuating units each configured to apply an actuating force capable of moving the second part relative to the first part. At least one of the (one or more) actuating units comprises: a body portion; an SMA (shape memory alloy) 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 forcemodifying 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. When viewed along a second axis that is perpendicular to the first axis, the actuator assembly, the first part and / or the second part have a first extent along a third axis that is perpendicular to the first and second axes, and the body portion of at least one of the actuating units has a second extent along the third axis. The second extent is more than half (50%) the first extent.

[0011] For example, when viewed along the first axis, the actuator assembly, the first part and / or the second part may comprise at least three major sides arranged in a loop around the first axis, and the first and second extents may be extents along one of the at least three major sides.

[0012] By having the body portion extend along the majority of the length of one of the at least three major sides, a relatively long body portion can be provided. The body portion acts as the lever of a lever system configured to modify the input force so as to give rise to the actuating force. It will be appreciated that the longer the body portion is (i.e. the longer the lever is), the larger the amplification that can be provided by the lever system is.

[0013] The first axis may be a primary axis which is defined with reference to the actuator assembly. The primary axis may extend through the actuator assembly, e.g. through the centre of the actuator assembly. The primary axis may be the longitudinal axis of the actuator assembly or an axis of rotational symmetry of at least some parts of the actuator assembly.

[0014] When viewed along such a first axis or primary axis, the angular extent of the body portion around the primary axis may be at least 60° or at least 90°.

[0015] When viewed along the first axis of the actuator assembly, the at least three major sides may comprise four major sides connected to each other via four corner portions so as to form a closed loop around the first axis. In other words, when viewed along the first axis of the actuator assembly, the first part and / or the second part may generally be quadrilateral in shape.

[0016] When viewed along the first axis of the actuator assembly, the at least three major sides may comprise three major sides connected to each other via three corner portions so as to form a closed loop around the first axis. In other words, when viewed along the first axis of the actuator assembly, the first part and / or the second part may generally be triangular in shape. Each of the at least three major sides may correspond to an edge of the first and / or second part, and the length of each side may be the length of the respective edge of the first and / or second part.

[0017] The length of the one of the at least three major sides may generally extend perpendicular to the first axis.

[0018] It will be appreciated that the body portion may extend parallel or generally parallel to the length of the one of the at least three major sides.

[0019] The second extent may be at least 60%, at least 70%, at least 80%, or at least 90% of the first extent. For example, the body portion may extend at least 60%, at least 70%, at least 80%, or at least 90% of the length of the one of the at least three major sides.

[0020] When viewed along the first axis, the actuator assembly, the first part and / or the second part may have a generally circular outline. As will be appreciated, in such examples, the first extent may correspond to the diameter of the circular outline.

[0021] It will be appreciated that a reference to a component being "connected between" two other components means, for example, that the component is directly or indirectly connected to each of the other components. Such an indirect connection may involve a connection via further component(s) (e.g. a connector) with fixed position(s) relative to one of the other components. Such an indirect connection may involve a connection via further component(s) which is / are movable relative to the other components. For example, an SMA element may be connected to the one of the first and second parts via a further flexure, e.g. as described in WO 2022 / 144541 (which is herein incorporated by reference to the maximum extent permissible by law).

[0022] Optionally, the force-modifying element is configured to at least partly define the pivot point (e.g. act as the fulcrum) of a first-class lever (i.e. a first-class lever system) comprising the body portion, wherein the lever is configured to modify the input force so as to give rise to the actuating force.

[0023] Optionally, the force-modifying element is configured to at least partly define the pivot point (e.g. act as the fulcrum) of a second-class lever (i.e. second-class lever system) or a third-class lever (i.e. a third-class lever system) comprising the body portion, wherein the lever is configured to modify the input force so as to give rise to the actuating force.

[0024] Optionally, the SMA element (generally longitudinally) extends along a first major side, the body portion (generally longitudinally) extends along a second major side, and the coupling link (generally longitudinally) extends along a third major side, wherein the first, second and third major sides are different adjacent sides (i.e. are different sides that are adjacent). The first, second and third major sides may be sequentially adjacent. The first and third major sides may be both adjacent to the second major side. It may be that the first and third major sides are not adjacent to each other.

[0025] Optionally, the SMA element (generally longitudinally) and the body portion (generally longitudinally) each extend along a first major side, and the coupling link (generally longitudinally) extends along a second major side, wherein the first and second major sides are different sides that are adjacent to each other. The first and second major sides are sequentially adjacent.

[0026] Optionally, the SMA element (generally longitudinally) extends along a first major side, the body portion (generally longitudinally) extends along a second and a third major side, and the coupling link (generally longitudinally) extends along a fourth major side, wherein the first, second, third, and fourth major sides are different adjacent sides (i.e. are different sides that that are adjacent). The first, second, third, and fourth major sides may be sequentially adjacent.

[0027] Optionally, the coupling link is compliant in a direction perpendicular to the actuating force.

[0028] Optionally, the force-modifying element is or comprises a force-modifying flexure.

[0029] Optionally, the force-modifying element is elongate and is stiff along its length and compliant in a direction perpendicular to its length.

[0030] Optionally, the force-modifying element forms part of a revolute joint (e.g. a pin joint).

[0031] Optionally, the force-modifying element is or comprises a contact bearing configured to engage a bearing surface of a bearing element of the one of the first and second parts, and configured to be capable of rolling and / or sliding relative to the bearing surface of the bearing element.

[0032] It will be appreciated that any reference to engagement of two components may refer to direct engagement or indirect engagement.

[0033] Wherein the force-modifying element is or comprises such a contact bearing, the bearing surface of the bearing element may extend perpendicular to the actuating force and / or the input force. Wherein the force-modifying element is or comprises such a contact bearing, the bearing element may comprise one or more end-stop surfaces configured to engage one or more complementary end-stop surfaces of the body portion so as to limit lateral movement of the body portion relative to the one of the first and second parts in directions perpendicular to the actuating force and / or the input force.

[0034] Wherein the force-modifying element is or comprises such a contact bearing, the body portion and the force-modifying element may together define a space within which the bearing element is provided.

[0035] Optionally, the force-modifying element is fixed relative to the body portion and defines the pivot point of a lever system configured to modify the input force so as to give rise to the actuating force.

[0036] Optionally, the coupling link is or comprises a coupling flexure.

[0037] Optionally, the coupling link is elongate and is stiff along its length and compliant in a direction perpendicular to its length.

[0038] Optionally, the coupling link is or comprises an SMA element.

[0039] Optionally, the body portion is integrally formed with the force-modifying element and / or the coupling link.

[0040] Optionally, the body portion comprises: a first portion extending between an end connected to the SMA element and an end connected to the force-modifying element; and a second portion extending between an end connected to the coupling link and an end connected to the force-modifying; wherein the first and second portions extend in directions that are angled relative to each other so as to form a space therebetween within which the force-modifying element is at least partly provided.

[0041] Optionally, the one or more actuating units comprise a plurality of actuating units, and the actuating forces of the plurality of actuating units are arranged with two-fold rotational symmetry about the first axis.

[0042] Optionally, the one or more actuating units comprise a plurality of actuating units, and the actuating forces of the plurality of actuating units are arranged to not have two-fold rotational symmetry about the first axis. Optionally, the at least one actuating unit comprises at least one pair of actuating units. For example, the at least one actuating unit may comprise two or four actuating units, i.e. one or two pairs of different actuating units.

[0043] Optionally, the coupling links of the at least one pair of actuating units overlap when viewed along the first axis. Alternatively, the coupling links of the at least one pair of actuating units may not overlap when viewed along the first axis.

[0044] Optionally, half of the at least one pair of actuating units are generally positioned closer to the first axis relative to the other half of the at least one pair of actuating units.

[0045] Optionally, the one or more actuating units comprise four actuating units arranged so as to be capable of moving the second part relative to the first part in any direction in a movement plane without applying any net torque to the second part about the first axis perpendicular to the movement plane; and, optionally, wherein a first pair of actuating units are each configured to apply a torque to the second part in one sense about the first axis, and a second pair of actuating units are each configured to apply a torque to the second part in the other sense about the first axis.

[0046] Optionally, the one or more actuating units are configured to tilt the second part relative to the first part about at least one axis perpendicular to the primary axis of the actuator assembly.

[0047] Optionally, the one or more actuating units comprise two, four or eight actuating units configured to tilt the second part relative to the first part about two axes perpendicular to the primary axis of the actuator assembly and to each other.

[0048] Optionally, the one or more actuating units are configured to move the second part relative to the first part along the primary axis of the actuator assembly.

[0049] Optionally, the one or more actuating units are configured to drive rotation of the second part relative to the first part around a primary axis, and the actuator assembly comprises a mechanism configured to convert the relative rotation driven by the actuating units around the primary axis into a secondary movement of the second part, or of a third part, relative to the first part.

[0050] The mechanism may be a helical bearing arrangement, and the secondary movement may be helical movement of the second part relative to the first part. In other words, the one or more actuating units may be configured to drive rotation of the second part relative to the first part around a primary axis, and the actuator assembly may comprise a helical bearing arrangement configured to convert the relative rotation driven by the actuating units around the primary axis into helical movement of the second part relative to the first part around the primary axis.

[0051] Optionally, the one or more actuating units comprises a plurality of actuating units arranged such that, for each direction along each axis of a Cartesian coordinate system, there is at least one actuating force with a non-zero component along that direction.

[0052] Optionally, the one or more actuating unit comprises eight actuating units arranged to provide three- dimensional translational movement of the second part relative to the first part.

[0053] Optionally, the first part or the second part comprises at least part of a lens and / or an image sensor.

[0054] Optionally, the primary axis of the actuator assembly is parallel to the optical axis of the lens and / or is perpendicular to a light-sensitive region of the image sensor.

[0055] Optionally, the first part or the second part comprises an emitter, a display, or a part thereof.

[0056] Optionally, the primary axis of the actuator assembly is perpendicular to a plane defined by the display and / or is parallel to the general direction in which radiation is emitted from the emitter.

[0057] In at least one of the actuating units, the body portion may rotate about an effective pivot axis during operation.

[0058] In at least one of the actuating units, the angle between the SMA element and the body portion may change by less than ±7.5° throughout an operating range of movement of the body portion. The operating range of movement may correspond to a range of movement of the body portion produced by actuation of the SMA element (by a controller). The operating range of movement may correspond to a range of movement of the body portion as defined at least in part by one or more endstops provided in the actuator assembly. Instead of ±7.5°, the maximum angular change may be ±5° or ±4° or ±3° or ±2°. As will be appreciated, amongst other things, any change in angle between the SMA element and the body portion changes the amplification of the actuating unit and therefore introduces nonlinearities into the behaviour of the actuating unit. Accordingly, minimising such changes in angle can make the actuating unit easier to control. The actuator assembly may have this feature in addition to, or as an alternative to, the feature that the second extent is more than half of the first extent. Hence, according to a second aspect of the present invention, there is provided an actuator assembly, the actuator assembly comprising: a first part; a second part that is movable relative to the first part; and one or more actuating units each configured to apply an actuating force capable of moving the second part relative to the first part. At least one of the actuating units comprises: 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. The angle between the SMA element and the body portion changes by less than ±7.5° throughout an operating range of movement of the body portion.

[0059] In at least one of the actuating units, the ratio of (a) a lever arm associated with the input force and the effective pivot axis to (b) the length of the SMA element may be greater than 0.2. This condition may apply at a centre of an operating range of movement of the body portion or throughout such an operating range. Instead of being greater than 0.2, the ratio may be greater than 0.25, greater than 0.3, greater than 0.35 or greater than 0.4. As will be appreciated, larger such ratios are associated with smaller changes in angle between the SMA element and the body portion for a given change in length of the SMA element. Hence, larger ratios can be advantageous for the reasons described above.

[0060] The actuator assembly may have this feature in addition to, or as an alternative to, the feature that the second extent is more than half of the first extent. Hence, according to a third aspect of the present invention, there is provided an actuator assembly, the actuator assembly comprising: a first part; a second part that is movable relative to the first part; and one or more actuating units each configured to apply an actuating force capable of moving the second part relative to the first part. At least one of the actuating units comprises: 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. The body portion rotates about an effective pivot axis during operation, and the ratio of (a) a lever arm associated with the input force and the effective pivot axis to (b) the length of the SMA element (i.e. a / b) is greater than 0.2. Brief description of the drawings

[0061] Certain embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which:

[0062] Figures 1A-E are schematic cross-sectional views of different variations of a camera assembly incorporating an actuator assembly;

[0063] Figure 2 is a schematic perspective view of the actuator assembly;

[0064] Figure 3 is a plan view of an actuating unit;

[0065] Figure 4 is a plan view of an actuating unit;

[0066] Figure 5 is plan view of an actuating unit in a first position;

[0067] Figure 6 is a plan view of the actuating unit of Figure 5 in a second position;

[0068] Figure 7 is a plan view of the actuating unit of Figure 5 in a third position;

[0069] Figure 8 is a schematic plan view of an arrangement of four actuating units;

[0070] Figure 9 is a plan view of an arrangement of four actuating units;

[0071] Figure 10 is a schematic plan view of the arrangement of Figure 9;

[0072] Figure 11 is a schematic plan view of an arrangement of four actuating units;

[0073] Figure 12 is a schematic plan view of an arrangement of four actuating units;

[0074] Figure 13 is a schematic plan view of an arrangement of four actuating units;

[0075] Figure 14 is a schematic plan view of an arrangement of four actuating units;

[0076] Figure 15 is a schematic plan view of an arrangement of four actuating units;

[0077] Figure 16 is a schematic plan view of an arrangement of four actuating units;

[0078] Figure 17 is a schematic perspective view of an arrangement of eight actuating units;

[0079] Figure 18 is a schematic plan view of an actuating unit;

[0080] Figure 19 is a schematic plan view of an actuating unit.

[0081] Detailed description

[0082] Camera

[0083] Figures 1A-E schematically show different variations of an apparatus 1 incorporating an actuator assembly 2. The apparatus 1 is, for example, a camera assembly 1. Generally, the apparatus 1 is to be incorporated in a portable electronic device such as a smartphone. Thus, miniaturisation can be an important design criterion.

[0084] Figure 2 schematically shows the actuator assembly 2. The actuator assembly 2 includes a support structure 10 and a movable part 20. The support structure 10 may be referred to as a 'first part' and the movable part 20 may be referred to as a 'second part'. The movable part 20 is movable relative to the support structure 10. When the actuator assembly 2 is included e.g. in the apparatus 1, the support structure 10 may be fixed relative to the main body of the apparatus 1. However, in general, the support structure 10 need not be stationary and may be movable relative to or within the apparatus 1. The actuator assembly 2 includes one or more actuating units 30. Each actuating unit 30 is configured to apply an actuating force to the movable part 20 capable of moving the movable part 20 relative to the support structure 10.

[0085] The movable part 20 may be supported (i.e. suspended) on the support structure 10 exclusively by the actuating units 30. Alternatively, the actuator assembly 2 may include a bearing arrangement 40 that supports the movable part 20 on the support structure 10. The actuating units 30 and the bearing arrangement 40 may together support the movable part 20 on the support structure 10. The bearing arrangement 40 may have any suitable form for allowing movement of the movable part 20 with respect to the support structure 10 with one or more degrees of freedom (DOFs). The actuating units 30 and / or the bearing arrangement 40 may constrain, i.e. reduce or prevent, other DOFs of movement of the movable part 20 relative to the support structure 10. For this purpose, the bearing arrangement 40 may, for example, include one or more of the following bearings: a rolling bearing (such as a ball bearing), a flexure bearing (i.e. an arrangement of flexures or other resilient elements that guide movement), or a plain (i.e. sliding contact) bearing.

[0086] A primary axis P, which may also be referred to as a 'first axis', can be defined with reference to the actuator assembly 2 and / or the support structure 10. The primary axis P may extend through the actuator assembly 2, e.g. through the centre of the actuator assembly 2. In some examples, the actuator assembly 2, the support structure 10 and / or the movable part 20 extends predominantly in a direction perpendicular to the primary axis P. In other words, the extent of the actuator assembly 2, the support structure 10 and / or the movable part 20 along the primary axis P is less than the extent thereof along any direction perpendicular to the primary axis P. The primary axis P may be the longitudinal axis of the actuator assembly 2 and / or the support structure 10. Alternatively or additionally, the support structure 10 and / or movable part 20 may include a planar component that extends perpendicularly to the primary axis P. Alternatively or additionally, in examples in which the apparatus 1 includes an optical element (such as a lens assembly 3) with an optical axis, or an imaging element (such as an imager sensor 4) with an imaging axis, the primary axis P may be parallel to such an axis and / or may coincide with such an axis when the movable part 20 is in a central position or orientation (for example, see Figure 1A).

[0087] In general, the movable part 20 may be movable relative to the support structure 10 with up to six degrees of freedom (DOFs). In the context of describing the DOFs of movement, the primary axis P may also be referred to as the z axis, and two further axes that are perpendicular to the primary axis P and to each other may be referred to as the x and y axes. The movable part 20 may be movable relative to the support structure 10 in all or in any subset (including only one) of the following DOFs:

[0088] • Tx and Ty: Translational movement in the x-y plane. In other words, the movable part 20 may be independently movable along the x and y axes. The movable part 20 may be movable to any position in the x-y plane within a range of movement. Instead of such planar movement, the movable part 20 may be movable linearly, e.g. along the x or y axis.

[0089] • Rx and Ry: Rotational movement (or simply rotation or tilting) about the x and y axes. In other words, the movable part 20 may be rotated about any axis perpendicular to the primary axis P. The movable part 20 may be rotatable to any rotational position (i.e. to any orientation) within a range of movement. Instead of such two-axis rotation, the movable part 20 may be rotatable about a single axis, e.g. about the x or y axis.

[0090] • Tz: Translational movement along the z axis. The movable part 20 may be movable to any translational position along the z axis within a range of movement.

[0091] • Rz: Rotational movement (or simply rotation) about the z axis. The movable part 20 may be rotatable to any rotational position (i.e. to any orientation) within a range of movement.

[0092] In some examples, the movable part 20 may be supported, e.g. by the bearing arrangement 40, so as to allow translational movement in the x-y plane (Tx, Ty) and / or rotational movement about the z axis (Rz). Translational movement along the z axis (Tz) and rotational movement about the x and y axes (Rx, Ry) may be constrained. Such support may be provided, for example, with a bearing arrangement 40 with a suitable arrangement of ball bearings or plain bearings which produce bearing forces in the +z direction and a biasing arrangement which produces a biasing force in the -z direction. Examples of actuator assemblies with such a bearing arrangement are disclosed in WO 2013 / 175197 Al and

[0093] WO 2017 / 072525 Al, each of which is herein incorporated by reference to the maximum extent permissible by law.

[0094] In some examples, the movable part 20 may be supported so as to allow tilting about the x and y axes (Rx, Ry) and optionally rotation about the z axis (Rz). The other DOFs of movement (i.e. Tx, Ty, Tz, Rz, or Tx, Ty, Tz) may be constrained. Such support may be provided by the bearing arrangement 40, for example in the form of a gimbal. Examples of such a bearing arrangement 40 are disclosed in WO 2021 / 209770 Al, which is herein incorporated by reference to the maximum extent permissible by law. Alternatively, such support may be provided exclusively by the actuating units 30, similarly to WO 2011 / 104518 Al which discloses an actuator assembly with eight SMA wires connected between the support structure 10 and the movable part 20. WO 2011 / 104518 Al is herein incorporated by reference to the maximum extent permissible by law.

[0095] In some examples, the movable part 20 may be supported so as to allow three-dimensional translational movement (Tx, Ty, Tz), while rotational movement (Rx, Ry, Rz) may be constrained. Such support may be provided by the bearing arrangement 40, for example in the form of nested linear bearings. Examples of such a bearing arrangement 40 are disclosed in WO 2021 / 209769 Al, which is herein incorporated by reference to the maximum extent permissible by law. Alternatively, such support may be provided exclusively by the actuating units 30, similarly to WO 2011 / 104518 Al.

[0096] The movable part 20 may, alternatively or additionally, move in other DOFs. The movable part 20 may move in DOFs that are a combination of any two or more of Tx, Ty, Tz, Rx, Ry and Rz. For example, the movable part 20 may move along a helical path (i.e. move helically) about the z axis, and so concurrently move along the z axis and rotate about the z axis. In other words, Tz and Rz movement may be coupled. An example of such a helical actuator assembly is disclosed in WO 2019 / 243849 Al, which is herein incorporated by reference to the maximum extent permissible by law.

[0097] The actuating units 30 are connected between the support structure 10 and the movable part 20. The actuating units 30 are arranged to apply actuating forces F (see e.g. Fig. 8) between the movable part 20 and the support structure 10. Selectively varying the actuating forces F may cause the movable part 20 to move relative to the support structure 10, for example within the DOFs allowed by the bearing arrangement 40. The actuating units 30 are thus capable of driving movement of the movable part 20 relative to the support structure 10.

[0098] The bearing arrangement 40 may cause the movable part 20 to move in directions which differ from the directions of the actuating forces F. In simple examples of this, one component of each actuating force F causes the movement of the movable part 20, and another component of each actuating force F acts against the bearing forces produced by the bearing arrangement 40.

[0099] The camera assembly 1 also includes a lens assembly 3 and an image sensor 4. The lens assembly 3 includes one or more lenses configured to focus an image on the image sensor 4. The lens assembly 3 defines an optical axis O. The lens assembly 3 may include a lens carrier, for example in the form of a cylindrical body, supporting the one or more lenses. The image sensor 4 captures an image and may be of any suitable type, for example a charge coupled device (CCD) or a complementary metal-oxide- semiconductor (CMOS) device. The camera assembly 1 may be a compact camera assembly in which each lens has a diameter of 20mm or less, for example of 12mm or less.

[0100] In the ("sensor-shift") variation of the camera assembly 1 shown in Figure 1A, the movable part 20 includes the image sensor 4. The lens assembly 3 may be fixed relative to the support structure 10, or may be movable relative to the support structure 10 along the optical axis O, as described below.

[0101] In the ("lens-shift") variation shown in Figure IB, the image sensor 4 is fixed relative to the support structure 10 and the movable part 20 includes the lens assembly 3. The lens assembly 3 may be movable relative to the movable part 20 along the optical axis O, as described below.

[0102] In both of these variations, the actuator assembly 2 is configured to move the lens assembly 3 relative to the image sensor 4 in any direction in the plane perpendicular to the primary axis P and hence the optical axis O. Such movement has the effect of moving the image on the image sensor 4 and enables optical image stabilisation (OIS) to be implemented in the camera assembly 1. In the sensor-shift variation, the movable part 20 may also be rotatable about the primary axis P so as to also enable compensation for roll.

[0103] In the ("module-tilt") variation shown in Figure 1C, the movable part 20 includes both the lens assembly 3 and the image sensor 4. Again, the lens assembly 3 may be movable relative to the movable part 20 along the optical axis O, as described below. The actuator assembly 2 is configured to tilt the movable part 20 about two axes perpendicular to the primary axis P and to each other, and optionally rotate the movable part 20 about the primary axis P, enabling OIS to be implemented in the camera assembly 1.

[0104] In the ("autofocus" or "zoom") variation shown in Figure ID, the movable part 20 includes the lens assembly 3, and the actuator assembly 2 moves the movable part 20 relative to the support structure 10 along the optical axis O. Such movement has the effect of adjusting the focus of the image on the image sensor 4 or providing zoom functionality. So, auto-focus (AF) or zoom functionality can be implemented in the camera assembly 1.

[0105] In some examples (not shown), the camera assembly 1 may include a first actuator assembly for providing OIS as illustrated in Figures 1A-C, and a second actuator assembly for providing AF or zoom as illustrated in Figure ID. One or both of the first and second actuator assemblies may correspond to actuator assemblies 2 as described herein. One of the first and second actuator assemblies may be another type of SMA actuator assembly or may be a non-SMA actuator assembly, e.g. a voice-coil motor (VCM) actuator assembly. As will be appreciated, in the lens-shift and module-tilt variations, the support structure 10 of the second actuator assembly 2 is fixed to (or corresponds to) the movable part 20 of the first actuator assembly 2.

[0106] In the ("AF+OIS") variation shown in Figure IE, the movable part 20 includes the lens assembly 3, and the actuator assembly 2 produces three-dimensional translational movement of the movable part 20 relative to the support structure 10, enabling both AF and OIS to be implemented using one actuator assembly 2.

[0107] Other variations are also possible. For example, in the autofocus variation or the AF+OIS variation, the movable part 20 may include the image sensor 4 rather than the lens assembly 3. The camera assembly 1 may include combinations of the above-described features, e.g. (a) lens shift and sensor shift, (b) module tilt and lens shift or sensor shift and autofocus, or (c) module tilt and AF+OIS.

[0108] The camera assembly 1 also includes a controller 8. The controller 8 may be implemented in an integrated circuit (IC) chip. The controller 8 generates drive signals for the actuating units 30, in particular for SMA elements 34 forming part of the actuating units 30. In the illustrated examples, the SMA elements 34 are SMA wires 34. SMA material has the property that, on heating, it undergoes a solid-state phase change that causes the SMA material to contract. Thus, applying drive signals to the SMA wires 34, thereby heating the SMA wires 34 by causing an electric current to flow, will cause the SMA wires 34 to contract and thus actuate the actuating unit 30 so as to drive relative movement of the movable part 20. The drive signals are chosen to drive relative movement of the movable part 20 in a desired manner, for example so as to achieve OIS by stabilizing the image sensed by the image sensor 4 or to achieve AF by adjusting the focus of the image sensed by the image sensor 4. The controller 8 supplies the generated drive signals to the SMA wires 34.

[0109] Optionally, the camera assembly 1 also includes a motion sensor (not shown), which may include a 3- axis gyroscope and a 3-axis accelerometer. The motion sensor can generate signals representative of the motion (specifically vibrations or "shake") of the camera assembly 1, which can be processed so as to produce signals representative of the required movement of the movable part 20 to compensate for such shake. The controller 8 receives such signals and can generate the drive signals for the SMA wires 34 to achieve OIS.

[0110] Although the actuator assembly 2 is described in connection with a camera assembly 1, it will be appreciated that the actuator assembly 2 may be used in any device in which movement of a movable part 20 relative to a support structure 10 is desired, e.g. to provide haptic feedback in a haptic feedback device or to move a projector or display in an augmented reality (AR) or virtual reality (VR) device. Actuating unit

[0111] Figure 3 shows a plan view of an example of the actuating unit 30.

[0112] A single actuating unit 30 is shown in Figure 3, but it will be appreciated that the actuator assembly 2 may generally have multiple actuating units 30, each of which may include the same components described with reference to Figure 3.

[0113] The actuating unit 30 includes a body portion 31 to which several other components of the actuating unit 30 are connected as described below. Typically, the body portion 31 is relatively rigid compared to the other components of the actuating unit, and does not deform significantly on actuation of the actuating unit 30.

[0114] The actuating unit 30 also includes a force-modifying element 32. In this example, the force-modifying element 32 is a force-modifying flexure 32. The force-modifying flexure 32 is connected between the body portion 31 and the support structure 10. One end of the force-modifying flexure 32 is connected to the body portion 31. The other end of the force-modifying flexure 32 is connected to the support structure 10, e.g. via a foot portion 36. The foot portion 36 is fixed relative to the support structure 10. The force-modifying flexure 32 allows the body portion 31 to pivot relative to the support structure 10 about an effective pivot point. The force-modifying flexure 32 is elongate and is stiff along its length and compliant in a direction perpendicular to its length.

[0115] The actuating unit 30 also includes an SMA element 34. In this example, the SMA element 34 is an SMA wire 34. The SMA wire 34 is connected between the body portion 31 and the support structure 10. One end of the SMA wire 34 is connected to the support structure 10, e.g. by a crimp 15. The other end of the SMA wire 34 is connected to the body portion 31, e.g. by a crimp 35.

[0116] The actuating unit 30 also includes a coupling link 33. In this example, the coupling link 33 is a coupling flexure 33. The coupling flexure 33 is connected between the body portion 31 and the movable part 20. One end of the coupling flexure 33 is connected to the body portion 31. The other end of the coupling flexure 33 is connected to the movable part 20. The coupling link 33 transfers or transmits an actuating force F from the body portion 31 to the movable part 20. The coupling link 33 is compliant (i.e. deformable) in a direction (or in multiple directions) perpendicular to the actuating force F. The coupling link is elongate, stiff along its length, and compliant in a direction perpendicular to its length. This allows the movable part 20 to move in directions other than the direction of the coupling flexure 33 and actuating force F. This can be needed, for example, where different actuating units 30 cause the movable part 20 to move in different directions.

[0117] In this example, the body portion 31, the force-modifying flexure 32, the coupling flexure 33 and the foot portion 36 are formed from different parts or materials. However, in other examples, the body portion 31 may be integrally formed with the force-modifying flexure 32, the coupling link 33, and / or the foot portion 36. For example, the body portion 31, the force-modifying flexure 32, the coupling flexure 33, and the foot portion 36 may be integrally formed from a single sheet of material (such as metal).

[0118] The force-modifying element 32 may form part of a conductive path via which the SMA element 34 and the first part 10 are electrically connected. This conductive path may be for electrically connecting, e.g. a control circuit / controller, a printed circuit board, and / or a power supply, to the SMA element 34.

[0119] The SMA wire 34 is arranged, on contraction, to apply an input force Fi on the body portion 31. In other words, the SMA element 34 is configured, on actuation, to apply an input force to the body portion 31. The input force Fi acts parallel to the length of the SMA wire 34. The force-modifying element 32 and the body portion 31 are configured to modify the input force Fi so as to give rise to the actuating force F, which is transmitted from the body portion 31 to the movable part 20 by the coupling flexure 33. In this particular example, the input force Fi deforms the force-modifying flexure 32, thereby causing the body portion 31 to pivot about the effective pivot point. In simple terms, the force-modifying element 32 and the body portion 31 form a lever system. That is, the force-modifying element 32 and the body portion 31 are configured to modify the direction and / or the magnitude of the input force Fi so as to give rise to the actuating force F.

[0120] In this example, the force-modifying element 32 is configured to define the pivot point (e.g. act as the fulcrum) of a first-class lever. However, in other examples, the force-modifying element 32 may instead be configured to define the pivot point of a second-class lever. Alternatively, as e.g. shown in Figure 16, the force-modifying element 32 may instead be configured to define the pivot point of a third-class lever.

[0121] In this example, the coupling flexure 33 is generally parallel to the SMA wire 34. In this example, the force-modifying flexure 32 also extends generally parallel to the SMA wire 34.

[0122] In this example, the force-modifying flexure 32 is placed in tension on contraction of the SMA wire 34.

[0123] This reduces the risk of buckling of the force-modifying flexure 32, reducing the risk of damage to the actuator assembly 2 and making the actuator assembly 2 more reliable. However, the force-modifying flexure 32 could instead be arranged so as to be placed under compression on contraction of the SMA wire 34. An arrangement in which the force-modifying flexure 32 is placed under compression is disclosed in WO 2022 / 084699 Al, which is herein incorporated by reference to the maximum extent permissible by law.

[0124] In this example, the force-modifying flexure 32 and the SMA wire 34 connect at one end to the support structure 10, and the coupling flexure 33 connects at one end to the movable part 20. In general, this arrangement may also be reversed, with the force-modifying flexure 32 and the SMA wire 34 connecting at one end to the movable part 20, and the coupling flexure 33 connecting at one end to the support structure 10. Where this is the case, the support structure 10 may be referred to as a 'second part' and the movable part 20 may be referred to as a 'first part'.

[0125] In this example, the ratio of (a) the lever arm associated with the input force Fi and the effective pivot point (cf feature 32 in the drawing) to (b) the length of the SMA wire 34 is around 0.25, i.e. greater than 0.2 and therefore potentially advantageous as described above. Also in this example, the angle between the SMA wire 34 and the body portion 31 changes by less than ±7.5° throughout an operating range of movement of the body portion 31 (for example for a maximum change in length of the SMA wire 34 of around 1%).

[0126] Figure 4 shows a plan view of an alternative example of the actuating unit 30. The description provided above in relation to the example of Figure 3 also applies to the example of Figure 4 except for the following differences.

[0127] In the example of Figure 4, the force-modifying element 32 is not a force-modifying flexure, but instead an element which forms part of a revolute joint, e.g. a pin joint. Specifically, the force-modifying element 32 comprises an opening 32 through which a bearing element (not shown) of the support structure 10 extends through, wherein the bearing element defines the pivot point of a lever system which comprises the body portion 31 as the lever and which is configured to modify the input force Fi so as to give rise to the actuating force F.

[0128] In the example of Figure 4, the body portion 31, the force-modifying element 32, and the coupling flexure 33 are integrally formed from a single sheet of material (such as a metal). However, in other examples, the body portion 31, the force-modifying element 32, and / or the coupling flexure 33 may be formed from different parts or materials. In the example of Figure 4, the input force Fi causes the body portion 31 to rotate relative to the support structure 10 about the pivot point at least partly defined by the force-modifying element 32.

[0129] In the example of Figure 4, the bearing element which extends through the opening 32 is configured to define the pivot point (e.g. act as the fulcrum) of a first-class lever. However, in other examples, the bearing element may instead be configured to define the pivot point of a second-class lever or a third- class lever.

[0130] In the example of Figure 4, the force-modifying element 32 and one end of the SMA wire 34 are connected to the support structure 10, and the coupling flexure 33 is connected at one end to the movable part 20. In general, this arrangement may also be reversed, with the force-modifying element 32 and one end of the SMA wire 34 being connected to the movable part 20, and the coupling flexure 33 being connected at one end to the support structure 10. Where this is the case, the support structure 10 may be referred to as a 'second part' and the movable part 20 may be referred to as a 'first part'.

[0131] Figure 5 shows a plan view of a further alternative example of the actuating unit 30. The description provided above in relation to the example of Figure 3 also applies to the example of Figure 5 except for the following differences.

[0132] In the example of Figure 5, the force-modifying element 32 is not a force-modifying flexure, but instead a contact bearing 32 configured to engage a bearing surface of a bearing element 11 of the support structure 10, and configured to be capable of rocking, rolling, and sliding relative to the bearing surface of the bearing element 11. The contact bearing 32 is fixed relative to the body portion 31 and defines the pivot point of a lever system which comprises the body portion 31 as the lever and which is configured to modify the input force Fi so as to give rise to the actuating force F.

[0133] In the example of Figure 5, the body portion 31 and the coupling flexure 33 are integrally formed from a single sheet of material (such as a metal), and the force-modifying element 32 is formed from a different part or material. However, in other examples, the force-modifying element 32 may also be integrally formed with the body portion 31 and the coupling flexure 33. Alternatively, the body portion 31 and the force-modifying element 32 may be formed from different parts or materials, and the body portion 31 may be integrally formed with the force-modifying element 32. Alternatively, the body portion 31, the coupling flexure 33, and the force-modifying element 32 may all be formed from different parts or materials. In the example of Figure 5, the input force Fi causes the body portion 31 to rock, roll and / or rotate relative to the support structure 10 about the pivot point defined by the force-modifying element 32 from engaging the bearing element 11.

[0134] In the example of Figure 5, the force-modifying element 32 and one end of the SMA wire 34 are connected to the support structure 10, and the coupling flexure 33 is connected at one end to the movable part 20. In general, this arrangement may also be reversed, with the force-modifying element 32 and one end of the SMA wire 34 being connected to the movable part 20, and the coupling flexure 33 being connected at one end to the support structure 10. Where this is the case, the support structure 10 may be referred to as a 'second part' and the movable part 20 may be referred to as a 'first part'.

[0135] In the example of Figure 5, as mentioned above, the force-modifying element 32 is a contact bearing 32 configured to engage a bearing surface of a bearing element 11 of the support structure 10, and defines the pivot point of a lever system which comprises the body portion 31 as the lever and which is configured to modify the input force Fi so as to give rise to the actuating force F.

[0136] The bearing surface of the bearing element 11 extends perpendicular to the actuating force F and the input force Fi, and the contact bearing 32 is configured to be capable of sliding along the bearing surface of the bearing element 11. In other words, the body portion 31 is configured to be capable of moving laterally relative to the support structure 10 in directions perpendicular to the actuating force F and the input force Fi.

[0137] Moreover, the body portion 31 and the contact bearing 32 together define a space within which the bearing element 11 is provided. This space limits the above-mentioned lateral movement of the body portion 31 relative to the support structure 10. In other words, the bearing element 11 comprises endstop surfaces configured to engage complementary end-stop surfaces of the body portion 31 so as to limit lateral movement of the body portion 31 relative to the support structure 10 in directions perpendicular to the actuating force F and the input force Fi. Figures 6 and 7 illustrate how these endstop surfaces engage to limit the lateral movement of the body portion 31 relative to the support structure 10. In Figure 6, the body portion 31 has been laterally shifted in a first direction (towards the right), from the central position shown in Figure 5, such that a first end-stop surface of the bearing element 11 engages a first complementary end-stop surface of the body portion 31. In Figure 7, the body portion 31 has been laterally shifted in a second, opposite direction (towards the left), from the position shown in Figure 5, such that a second end-stop surface of the bearing element 11 engages a second complementary end-stop surface of the body portion 31. Furthermore, as the contact bearing 32, which is fixed relative to the body portion 31, defines the pivot point of the lever system, the effort distance Lin and the load distance Lout of the lever system is unaffected by the lateral movement of the body portion 31 relative to the support structure 10. In other words, the amplification of the lever system is independent from the lateral positioning of the body portion 31 relative to the support structure 10. This is illustrated by how the effort distance Linand the load distance Lout remain unchanged in Figures 5, 6 and 7. Making the amplification of the lever system independent from the lateral positioning of the body portion 31, makes it easier to accurately control the performance of the actuating unit 30.

[0138] In the above-described examples, the actuating unit 30 includes a coupling link 33 in the form of a coupling flexure 33. The purpose of the coupling link 33 is to allow movement of the movable part 20 in directions perpendicular to the actuating force F. In general, however, the actuating unit 30 need not include such a coupling link 33, e.g. in examples in which there is no movement of the movable part 20 in directions perpendicular to the actuating force F. Furthermore, the coupling link 33 may be embodied by components other than the coupling flexure 33, for example by a ball bearing or plain bearing configured to transmit the actuating force F to the movable part 20 while allowing movement of the movable part 20 in directions perpendicular to the actuating force F. Such alternative examples of the coupling link 33 are disclosed in WO 2022 / 084699 Al. The coupling link 33 may (or may not) be formed by an SMA wire, which may (or may not) be integral with the SMA wire 34 and may (or may not) be driven together with the SMA wire 34.

[0139] Furthermore, instead of the above-described force-modifying elements 32, the actuator assembly may include a different type of force-modifying element 32 configured to enable the above-described movement of the body portion 31 relative to the support structure 10. Such a force-modifying element 32 may include, for instance, a rigid member with one end connected to the support structure 10 via a suitable pivoting connection (e.g. a pin joint) and the other end connected to the body portion 31.

[0140] In the example of Figure 5, the body portion 31 comprises a first portion extending between an end connected to the SMA element 34 and an end connected to the force-modifying element 32. Furthermore, the body portion 31 comprises a second portion extending between an end connected to the coupling link 33 and an end connected to the force-modifying 32. These first and second portions of the body portion 31 extend in directions that are angled relative to each other so as to form a space therebetween within which the force-modifying element 32 is at least partly provided. This can help the actuating unit 30 be more compact in size. It will be appreciated that the example of Figure 3 may also comprise such first and second portions arranged to form a space therebetween within which the force- modifying element 32 is at least provided, as e.g. illustrated in Fig. 12. The same applies to the example of Figure 4 and other alternative examples described herein.

[0141] Arrangement of four actuating units

[0142] Figure 8 schematically shows a plan view of an example of the actuator assembly 2 having an arrangement of actuating units 30 (not shown) each applying an actuating force F. In this example, the actuator assembly 2 includes a total of four actuating units 30. The four actuating units 30 are configured to apply actuating forces F between the movable part 20 and the support structure 10. The actuating forces F are applied to the movable part 20 relative to the support structure 10.

[0143] The arrangement of actuating units 30 of Figure 8 may be used, for example, in examples in which the movable part 20 is movable relative to the support structure 10 in a movement plane. So, Tx, Ty and optionally Rz movement of the movable part 20 may be allowed.

[0144] The four actuating units 30 of Figure 8 are in an arrangement capable of applying actuating forces F so as to move the movable part 20 relative to the support structure 10 to any position within a range of movement. The range of movement may be within a movement plane that is perpendicular to the primary axis P.

[0145] In particular, two actuating units 30 (e.g. the actuating units 30 providing the top and bottom actuating forces F in Figure 8) are arranged to apply actuating forces F in opposite directions parallel to a first axis (e.g. the x axis). The other two actuating units (e.g. the actuating units 30 providing the left and right actuating units in Figure 8) are arranged to apply actuating forces F in opposite directions parallel to a second axis (e.g. the y axis), perpendicular to the first axis. By appropriately varying the difference in actuation amount between the opposing actuating units 30, the movable part 20 may thus be moved independently along the first and second axes. The opposing actuating forces F are not colinear, but offset from each other in a direction perpendicular to the actuating forces F. Providing opposing actuating units 30 allows the tension in the SMA wires 30 of the respective actuating units 30 to be controlled, allowing for more accurate and reliable positioning of the movable part 20 compared to a situation in which actuating units 30 do not oppose each other.

[0146] None of the actuating forces F are collinear. This allows the arrangement of actuating units 30 to translationally move the movable part 20 without applying any net torque to the movable part 20 about the primary axis P. So, the movable part 20 can be moved translationally in the movement plane without rotating the movable part 20 in the movement plane. In general, the arrangement of actuating units 30 is capable of accurately controlling a torque or moment of the movable part 20 about the primary axis P. So, the actuating units 30 are capable of rotating (or not rotating) the movable part 20 relative to the support structure about the primary axis P.

[0147] In particular, two actuating units 30 (e.g. the actuating units 30 providing the top and bottom actuating forces F in Figure 8) are arranged to apply actuating forces F so as to generate a torque or moment between the movable part 20 and the support structure 2 in a first sense (e.g. anti-clockwise) around the primary axis P. The other two actuating units 30 (e.g. the actuating units 30 providing the left and right actuating forces F in Figure 8) are arranged to apply actuating forces F so as to generate a torque or moment between the movable part 20 and the support structure 2 in a second, opposite sense (e.g. clockwise) around the primary axis P. This allows the movable part 20 to be rotated by simultaneously increasing or decreasing the tension of SMA wires in any of the two actuating units 30.

[0148] As shown, two actuating units 30 may be arranged to apply actuating forces F in a corner of the actuator assembly 2. The other two actuating units 30 may be arranged to apply actuating forces F in another, opposite corner of the actuator assembly 2.

[0149] The actuator assembly 2, and in particular the movable part 20 and / or the support structure 10, have a generally quadrilateral footprint. In other words, when viewed along the primary axis P, the support structure 10 and / or the movable part 20 comprise four major sides arranged in a loop around the primary axis P. When viewed along the primary axis P, the four major sides are connected to each other via four corner portions so as to form a closed loop around the primary axis P. Each of the four major sides may correspond to an edge of the support structure 10 and / or the movable part 20, and the length of each major side may be the length of the respective edge of the support structure 10 and / or the movable part 20. The length of the four major sides generally extend perpendicular to the primary axis P.

[0150] The arrangement of actuating forces F applied between movable part 20 and support structure 10 corresponds to the arrangement of SMA wires 30 described in WO2013 / 175197 Al, which is herein incorporated by reference to the maximum extent permissible by law.

[0151] Figure 9 shows a plan view of four of the actuating units 30 of Figure 3 arranged to provide four actuating forces F as shown in Figure 8 around a generally quadrilateral actuator assembly 2. Figure 10 is a simplified schematic diagram of the arrangement of Figure 9.

[0152] In the example of Figures 9 and 10, the body portion 31 of each actuating unit 30 (comprising actuating units 30-1, 30-2, 30-3, 30-4) extends along the majority (i.e. more than 50%) of the length of one of the four major sides of the generally quadrilateral footprint of the actuator assembly 2. The body portion 31 of each actuating unit 30 may extend at least 60%, at least 70%, at least 80%, or at least 90% of the length of one of the four major sides. Each body portion 31 extends parallel or generally parallel to the length of one of the four major sides.

[0153] By having the body portions 31 of an actuating unit 30 extend along the majority of the length of one of the four major sides, a relatively long body portion 31 can be provided. The body portion 31 acts as the lever of a lever system configured to modify the input force Fi so as to give rise to the actuating force F. As such, it will be appreciated that the longer the body portion 31 is (i.e. the longer the lever is), the larger the amplification that can be provided by the lever system is.

[0154] The body portions 31 of the four actuating units 30 are arranged in a loop around the primary axis P. That is, the body portions 31 of the four actuating units 30 each extend along different major sides.

[0155] Similarly, the SMA element 34 of each actuating unit 30 also extends along the majority (i.e. more than 50%) of the length of one of the four major sides of the generally quadrilateral footprint of the actuator assembly 2. The SMA element 34 of each actuating unit 30 may extend at least 60%, at least 70%, at least 80%, or at least 90% of the length of one of the four major sides. Each SMA element 34 extends parallel or generally parallel to the length of one of the four major sides. However, it will be appreciated that this is optional.

[0156] By having the SMA element 34 of an actuating unit 30 extend along the majority of the length of one of the four major sides, a relatively long SMA element 34 can be provided. It will be appreciated that the longer the SMA element 34 is, the larger the contraction (i.e. stroke) that can be provided by the SMA element 34 is.

[0157] Similarly, the coupling link 33 of each actuating unit 30 also extends along the majority (i.e. more than 50%) of the length of one of the four major sides of the generally quadrilateral footprint of the actuator assembly 2. The coupling link 33 of each actuating unit 30 may extend at least 60%, at least 70%, at least 80%, or at least 90% of the length of one of the four major sides. Each coupling link 33 extends parallel or generally parallel to the length of one of the four major sides. However, it will be appreciated that this is optional.

[0158] By having the coupling link 33 of an actuating unit 30 extend along the majority of the length of one of the four major sides, a relatively long coupling link 33 can be provided. It will be appreciated that the longer the coupling link 33 is, the more compliant it can be in directions perpendicular to its length. Within each actuating unit 30, the SMA element 34 extends along a first major side, the body portion 31 extends along a second major side, and the coupling link 33 extends along a third major side, wherein the first, second and third major sides are different sides that are adjacent to each other. As such, within each actuating unit 30, the SMA element 34 and the coupling link 33 are provided on opposite major sides.

[0159] The actuating units 30 are arranged with two-fold rotational symmetry about the primary axis P, such that e.g. the central axis of the movable part 20 and / or the arrangement of actuating units 30 coincides with the primary axis P when all the actuating units 30 are actuated to provide equal amounts of actuating force F.

[0160] When viewed along the primary axis P, the body portions 31 and the coupling links 33 of the actuating units 30 overlap with each other, but the SMA elements 34 do not overlap with each other nor with any of the body portions 31 and coupling links 33.

[0161] Figure 11 shows a schematic plan view of four actuating units 30 also arranged to provide four actuating forces F as shown in Figure 8 but mirrored about the y axis (one would appreciate that this does not change how the actuator assembly 2 is capable of moving the movable part 20 relative to the support structure 10). In Figure 11, like with Figures 13 to 16, the SMA elements 34 and coupling links 33 of the actuating units 30 are not shown for simplicity. The description provided above in relation to the arrangement of Figures 9 and 10 also apply to the arrangement of Figure 11.

[0162] Additionally, in the example of Figure 11, within each actuating unit 30, the body portion 31 comprises a first portion extending between an end connected to the SMA element 34 (not shown for simplicity) and an end connected to the force-modifying element 32. Furthermore, within each actuating unit 30, the body portion 31 comprises a second portion extending between an end connected to the coupling link 33 (not shown for simplicity) and an end connected to the force-modifying 32. The first and second portions of each of these actuating units 30 extend in directions that are angled relative to each other so as to form a space therebetween within which the force-modifying element 32 is at least partly provided as shown in Figure 12. This can help each actuating unit 30 to be more compact.

[0163] Figure 13 shows a schematic plan view of an arrangement of four of actuating units 30 that is identical to the arrangement of Figure 11 but differs in that, in the arrangement of Figure 13, a pair of adjacent actuating units 30 (i.e. the pair of actuating units 30 located closest to the lower right corner of the actuator assembly 2) are generally positioned closer to the primary axis P relative to the other pair of adjacent actuating units 30 (i.e. the pair of actuating units 30 located closest to the upper left corner of the actuator assembly 2) when viewed along the primary axis P.

[0164] The description provided above in relation to the arrangement of Figures 9 and 10 also applies to the arrangement of Figure 13 except for the following differences.

[0165] In the arrangement of Figure 13, the actuating forces F of the four actuating units 30 are arranged to not have two-fold rotational symmetry about the primary axis P. As such, when all the actuating units 30 are actuated to provide equal amounts of actuating force F, the central axis of the movable part 20 and / or the arrangement of actuating units 30 does not coincide with (i.e. is spaced from) the primary axis P.

[0166] In the arrangement of Figure 13, when viewed along the primary axis P, the coupling links 33 of the actuating units 30 do not overlap with each other and with any the body portions 32. This may help improve the performance of the actuator assembly 2.

[0167] Like with the arrangement of Figure 11, each actuating unit 30 of Figure 13 also comprises a body portion 31 having first and second portions forming a space therebetween within which the forcemodifying element 32 is at least partly provided. However, it will be appreciated that this is optional.

[0168] Figure 14 shows a schematic plan view of an arrangement of four of actuating units 30 that is identical to the arrangement of Figure 11 but differs in that, in the arrangement of Figure 14, a pair of actuating units 30 provided on opposing sides of the primary axis P (i.e. the pair of actuating units 30 located on the upper and lower sides of the actuator assembly 2) are generally positioned closer to the primary axis P relative to the other pair of actuating units 30 also provided on opposing sides of the primary axis P (i.e. the pair of actuating units 30 located on the left and right sides of the actuator assembly 2) when viewed along the primary axis P. The arrangement of Figure 14 also differs in that the pair of actuating units 30 located on the upper and lower sides of the actuator assembly 2 comprise body portions 31 that have the first and second portions angled inwards (rather than outwards) from the ends thereof connected to the force-modifying element 32; however, it will be appreciated that this is optional.

[0169] The description provided above in relation to the arrangement of Figures 9 and 10 also applies to the arrangement of Figure 14 except for the following differences.

[0170] In the arrangement of Figure 14, when viewed along the primary axis P, the coupling links 33 of the actuating units 30 do not overlap with each other nor with any of the body portions 32. Moreover, the coupling links 33 also do not overlap with the SMA elements 34 when viewed along the primary axis P.

[0171] This may help improve the performance of the actuator assembly 2.

[0172] Like with the arrangement of Figure 11, each actuating unit 30 of Figure 14 also comprises a body portion 31 having first and second portions forming a space therebetween within which the forcemodifying element 32 is at least partly provided. However, it will be appreciated that this is optional.

[0173] In the arrangement of Figure 14, it will be appreciated that the pair of actuating units 30 located on the upper and lower sides of the actuator assembly 2 may comprise shorter body portions 31 compared to the body portions 31 of the pair of actuating units 30 located on the left and right sides of the actuator assembly 2. However, this may not necessarily be the case.

[0174] Figure 15 shows a schematic plan view of four actuating units 30 arranged to provide four actuating forces F as shown in Figure 8 but, again, mirrored about the y axis. The description provided above in relation to the arrangement of Figures 9 and 10 also apply to the arrangement of Figure 15 except for the following differences.

[0175] In the arrangement of Figure 15, within each actuating unit 30, the SMA element 34 and most of the body portion 31 both extend along a first major side parallel to each other, and the coupling link 33 extends along a second major side perpendicular or generally perpendicular to the first major side, wherein the first and second major sides are different sides that are adjacent to each other.

[0176] In the arrangement of Figure 15, when viewed along the primary axis P, the coupling links 33 overlap with each other, but do not overlap with the body portions 31.

[0177] At least one of the actuating units 30 of Figure 15 may comprise, when viewed along the primary axis P, an SMA element 34 which overlaps with the body portion 31 as shown in Figure 18.

[0178] Figure 16 shows a schematic plan view of four actuating units 30 arranged to provide four actuating forces F as shown in Figure 8 but with the actuating forces F reversed in direction (which one would appreciate does not change how the actuator assembly 2 is capable of moving the movable part 20 relative to the support structure 10). In Figure 16, each actuating unit 30 comprises a third-class lever (instead of a first-class lever) comprising the body portion 31 as a lever configured to modify the input force Fi so as to give rise to the actuating force F. The description provided above in relation to the arrangement of Figures 9 and 10 also apply to the arrangement of Figure 16 except for the following differences. In the arrangement of Figure 16, when viewed along the primary axis P, the coupling links 33 overlap with each other, and may also overlap with the SMA wires 34, but do not overlap with the body portions 31.

[0179] In Figures 8 to 16, the actuating forces F are perpendicular to the primary axis P, and may be parallel to the movement plane. However, in general the actuating forces F may be angled relative to the movement plane. The actuating forces F may thus have a component along the primary axis P. This component along the primary axis P may be resisted by the bearing arrangement 40, for example, to provide movement of the movable part 20 in degrees of freedom allowed by the bearing arrangement 40. In some examples, it may even be desirable for actuating forces F to have a component in parallel to the primary axis P, for example so as to load plain or rolling bearings arranged between the movable part 20 and the support structure 10.

[0180] Although the arrangements of Figures 8 to 16 was described as being for relatively moving the movable part 20 in the movement plane (e.g. translationally along the x and y axis, or rotationally about the primary axis P), in other examples these arrangements of actuating units 30 may be configured to move the movable part 20 relative to the support structure 10 differently. For example, the same arrangements may be used to tilt the movable part 20 relative to the support structure 10 about axes perpendicular to the primary axis P, due to appropriate movement constraints provided by the bearing arrangement 40. For example, the bearing arrangement 40 may include a plurality of flexures for guiding tilting of the movable part 20 about the axes perpendicular to the primary axis P. Examples of such bearing arrangement 40 are described in WO2022 / 029441 Al, which is herein incorporated by reference to the maximum extent permissible by law.

[0181] Although the arrangements of Figure 8 to 16 each comprise four actuating units 30, in general these arrangements may each include fewer actuating units 30. For example, these arrangements may include two actuating units 30, e.g. the two actuating units 30 providing the actuating forces F depicted in the top right of Figure 8. The forces applied to the movable part 20 by the two actuating units 30 may be opposed by a biasing force of one or more resilient elements, such as springs. With reference to Figure 8, the two actuating units 30 providing the actuating forces F in the bottom left corner may be replaced with springs applying biasing forces along the corresponding depicted arrows, for example. units

[0182] Figure 17 schematically shows a perspective view of an actuator assembly 2 with a total of eight actuating units 30 (not shown for simplicity) each configured to apply actuating forces F between the movable part 20 and the support structure 10 (also not shown for simplicity). The actuating forces F are applied to the movable part 20 relative to the support structure 10.

[0183] At least one of the eight actuating units 30 may be similar to the ones described in relation to Figures 3 to 7. In other words, at least one of the eight actuating units 30 may comprise:

[0184] • a body portion 31;

[0185] • an SMA element 34 connected between the body portion 31 and one of the support structure 10 and the movable part 20, and configured, on actuation, to apply an input force Fi to the body portion 31;

[0186] • a force-modifying element 32 connected between the body portion 31 and the one of the support structure 10 and the movable part 20, and configured to modify the input force Fi so as to give rise to one of the actuating forces F shown in Figure 17; and

[0187] • a coupling link 33 connected between the body portion 31 and the other of the support structure 10 and the movable part 20, wherein the coupling link 33 is configured to transmit the actuating force F from the body portion 31 to the other of the support structure 10 and the movable part 20.

[0188] When viewed along the primary axis P, the support structure 10 and / or the movable part 20 comprises four major sides arranged in a loop around the primary axis P. The body portion of the at least one actuating unit 30 may extend along the majority (i.e. more than 50%; e.g. at least 60%, at least 70%, at least 80%, or at least 90%) of the length of one of the four major sides, similar to how the body portions 31 of the actuating units 30 of Figures 9 to 16 are arranged.

[0189] The arrangement of actuating units 30 of Figure 17 may be used, for example, in examples in which the movable part 20 is movable relative to the support structure 10 in three translational degrees of freedom (Tx, Ty, Tz) (see Figure IE) or in two or three rotational degrees of freedom (Rx, Ry or Rx, Ry, Rz) (see Figure 1C). The eight actuating units 30 may be arranged to provide three-dimensional translational movement of the movable part 20 relative to the support structure 10.

[0190] The eight actuating units 30 may be arranged such that their actuating forces F are oriented or arranged in a manner equivalent to the orientation or arrangement of the forces applied by the eight SMA wires in the actuator assemblies disclosed in WO 2011 / 104518 Al.

[0191] As shown in Figure 17, the eight actuating units 30 may be arranged such that, for each direction along each axis of a Cartesian coordinate system, there is at least one actuating force F with a non-zero component along that direction. More specifically, the actuating forces F (e.g. when visualised as vectors at particular positions in space) are arranged on each of four sides (i.e. a first side, a second side, a third side and then a fourth side) around the primary axis P. The two actuating forces F on each side are inclined in opposite senses relative to a plane perpendicular to the primary axis P, when viewed perpendicular from the primary axis P. The four sides on which the actuating forces F are arranged extend in a loop around the primary axis P. In this example, adjacent sides are perpendicular to each other, and the sides form a square when viewed along the primary axis P, but alternatively the sides could take a different e.g. quadrilateral shape. In this example, the actuating forces F are parallel to the outer faces of the square envelope of the movable part 20 but this is not essential.

[0192] Four actuating forces F, including one actuating force F on each of the sides, form a 'first' group that have a component in one direction ('upwards' or +z) and the other four actuating forces F form a 'second' group that have a component in the opposite direction ('downwards' or -z). Herein, 'up' and 'down' refer to opposite directions along the primary axis P.

[0193] The first group of actuating forces F and the second group of actuating forces F are each arranged with two-fold rotational symmetry about the primary axis P. As a result of this symmetrical arrangement, different combinations of the actuating forces F are capable of driving movement of the movable part 20 with multiple degrees of freedom, as follows.

[0194] The first group of actuating forces F, when generated together, drive upwards (+z) movement, and the second group of actuating forces F, when generated together, drive downwards (-z) movement.

[0195] Within each group, adjacent pairs of actuating forces F, when differentially generated, drive tilting about a lateral axis perpendicular to the primary axis P (e.g. Rx or Ry movement).

[0196] Sets of four actuating forces F, including two actuating forces F from each group, when generated together, drive movement along a lateral axis perpendicular to the primary axis P (e.g. Tx or Ty movement).

[0197] The actuator assembly 2 may have other specific arrangements of actuating units to those shown in Figure 17. For example, strict symmetry is not required. Furthermore, instead of there being an up- pulling actuating unit and a down-pulling actuating unit on each side, there may be two up-pulling actuating units on each of two opposite sides (e.g. the first and third sides) and two down-pulling actuating units on the other two sides (e.g. the second and fourth sides). Other variations

[0198] It will be appreciated that there may be many other variations of the above-described examples.

[0199] For example, although in all of the illustrated examples the actuator assembly 2, in particular the movable part 20 and / or the support structure 10, have a generally quadrilateral footprint, it will be appreciated that in other examples the actuator assembly 2 may have a generally triangular footprint. In other words, when viewed along the primary axis P, the support structure 10 and / or the movable part 20 may comprise three major sides arranged in a loop around the primary axis P. When viewed along the primary axis P, the three major sides may be connected to each other via three corner portions so as to form a closed loop around the primary axis P. Each of the three major sides may correspond to an edge of the support structure 10 and / or the movable part 20, and the length of each major side may be the length of the respective edge of the support structure 10 and / or the movable part 20. The length of the three major sides may generally extend perpendicular to the primary axis P. In other examples, the actuator assembly 10, the movable part 20 and / or the support structure 10 may have a generally circular footprint.

[0200] For example, it will be appreciated that at least one of the actuating units 30 of the illustrated examples, may be arranged as shown in Figure 19, wherein the SMA element 34 (generally longitudinally) extends along a first major side, the body portion 31 (generally longitudinally) extends along a second and a third major side, and the coupling link 33 (generally longitudinally) extends along a fourth major side, wherein the first, second, third, and fourth major sides are different adjacent sides. As shown in Figure 19, the first, second, third, and fourth major sides are sequentially adjacent.

[0201] For example, the actuator assembly 2 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 Al, a V-shaped SMA wire with a compliant connector as disclosed in WO 2013 / 121225 Al, a scissor jack arrangement as disclosed in WO 2021 / 156458 Al, a two-stage arrangement as disclosed in WO 2021 / 111181 Al, or simply an SMA wire connected between the support structure 10 and the movable part 20. 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.

[0202] For example, although in all of the illustrated examples the actuating units 30 are configured to amplify the stroke provided by the contraction of the SMA element 34, it will be appreciated that in other examples the actuating units 30 may be configured to instead amplify the force applied by the SMA element 34, or to simply re-direct the force applied by the SMA element 34 without providing any amplification of stroke or force.

[0203] As discussed above, the support structure 10 or the movable part 20 may comprise at least part of a lens and / or an image sensor. The primary axis P of the actuator assembly 2 may be parallel to the optical axis of the lens and / or perpendicular to a light-sensitive region of the image sensor.

[0204] As partly discussed above, the support structure 10 or the movable part 20 may comprise an emitter, a display, or a part thereof. The primary axis P of the actuator assembly 2 may be perpendicular to a plane defined by the display and / or parallel to the general direction in which radiation is emitted from the emitter.

[0205] As discussed above, one or more of the above-described actuating units 30 may be configured to tilt the movable part 20 relative to the support structure 10 about at least one axis perpendicular to the primary axis P of the actuator assembly 2, e.g. so as to provide OIS.

[0206] As discussed above, two, four, or eight of the above-described actuating units 30 may be configured to tilt the movable part 20 relative to the support structure 10 about two axes perpendicular to the primary axis P and to each other, e.g. so as to provide OIS.

[0207] As discussed above, one or more of the above-described actuating units 30 may be configured to move the movable part 20 relative to the support structure 10 along the primary axis P, e.g. so as to provide AF functionality.

[0208] As discussed above, one or more of the above-described actuating units 30 may be configured to drive rotation of the movable part 20 relative to the support structure 10 around the primary axis P, and a helical bearing arrangement may be configured to convert the relative rotation driven by the actuating units 30 around the primary axis P into helical movement of the movable part 20 relative to the support structure 10 around the primary axis P, e.g. so as to provide AF functionality.

[0209] SMA

[0210] The above-described 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 (e.g. 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, e.g. a thermal shape memory effect or a magnetic shape memory effect, and may be controlled in any suitable way, e.g. by Joule heating, another heating technique or by applying a magnetic field.

Claims

Claims1. An actuator assembly having a first axis, the actuator assembly comprising: a first part; a second part that is movable relative to the first part; and one or more actuating units each configured to apply an actuating force capable of moving the second part relative to the first part, wherein at least one of the actuating units comprises: a body portion; an SMA (shape memory alloy) 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; wherein, when viewed along a second axis that is perpendicular to the first axis, the actuator assembly, the first part and / or the second part have a first extent along a third axis that is perpendicular to the first and second axes, and the body portion has a second extent along the third axis, where the second extent is more than half the first extent.

2. An actuator assembly according to claim 1, wherein, when viewed along the first axis, the actuator assembly, the first part and / or the second part comprise at least three major sides arranged in a loop around the first axis, and wherein the first and second extents are extents along one of the at least three major sides.

3. An actuator assembly according to claim 1 or 2, wherein the force-modifying element is configured to at least partly define the pivot point of a first-class lever comprising the body portion, wherein the lever is configured to modify the input force so as to give rise to the actuating force.

4. An actuator assembly according to claim 2 or claim 3 when dependent on claim 2, wherein the SMA element extends along a first major side, the body portion extends along a second major side, and the coupling link extends along a third major side, wherein the first, second and third major sides are different adjacent sides; or wherein the SMA element and the body portion each extend along a first major side, and the coupling link extends along a second major side, wherein the first and second major sides are different adjacent sides.

5. An actuator assembly according to any preceding claim, wherein the coupling link is compliant in a direction perpendicular to the actuating force.

6. An actuator assembly according to any preceding claim, wherein the force-modifying element is or comprises a force-modifying flexure; and / or wherein the force-modifying element is elongate and is stiff along its length and compliant in a direction perpendicular to its length.

7. An actuator assembly according to any preceding claim, wherein the force-modifying element is or comprises a contact bearing configured to engage a bearing surface of a bearing element of the one of the first and second parts, and configured to be capable of rolling and / or sliding relative to the bearing surface of the bearing element.

8. An actuator assembly according to claim 7, wherein the bearing surface of the bearing element extends perpendicular to the actuating force and / or the input force.

9. An actuator assembly according to claim 7 or 8, wherein the bearing element comprises one or more end-stop surfaces configured to engage one or more complementary end-stop surfaces of the body portion so as to limit lateral movement of the body portion relative to the one of the first and second parts in directions perpendicular to the actuating force and / or the input force.

10. An actuator assembly according to any of claims 7 to 9, wherein the body portion and the forcemodifying element together define a space within which the bearing element is provided.

11. An actuator assembly according to any preceding claim, wherein the force-modifying element is fixed relative to the body portion and defines the pivot point of a lever system configured to modify the input force so as to give rise to the actuating force.

12. An actuator assembly according to any preceding claim, wherein the coupling link is or comprises a coupling flexure; and / or optionally, wherein the coupling link is elongate and is stiff along its length and compliant in a direction perpendicular to its length.

13. An actuator assembly according to any preceding claim, wherein the body portion comprises: a first portion extending between an end connected to the SMA element and an end connected to the force-modifying element;a second portion extending between an end connected to the coupling link and an end connected to the force-modifying element; wherein the first and second portions extend in directions that are angled relative to each other so as to form a space therebetween within which the force-modifying element is at least partly provided.

14. An actuator assembly according to any preceding claim, wherein the one or more actuating units comprise a plurality of actuating units, and the actuating forces of the plurality of actuating units are arranged with two-fold rotational symmetry about the first axis.

15. An actuator assembly according to any of claims 1 to 13, wherein the one or more actuating units comprise a plurality of actuating units, and the actuating forces of the plurality of actuating units are arranged to not have two-fold rotational symmetry about the first axis.

16. An actuator assembly according to any preceding claim, wherein the at least one actuating unit comprises at least one pair of actuating units.

17. An actuator assembly according to claim 16, wherein the coupling links of the at least one pair of actuating units overlap when viewed along the first axis.

18. An actuator assembly according to claim 16, wherein the coupling links of the at least one pair of actuating units do not overlap when viewed along the first axis.

19. An actuator assembly according to any of claims 16 to 18, wherein half of the at least one pair of actuating units are generally positioned closer to the first axis relative to the other half of the at least one pair of actuating units.

20. An actuator assembly according to any preceding claim, wherein the one or more actuating units comprise four actuating units arranged so as to be capable of moving the second part relative to the first part in any direction in a movement plane without applying any net torque to the second part about the first axis perpendicular to the movement plane; and, optionally, wherein a first pair of actuating units are each configured to apply a torque to the second part in one sense about the first axis, and a second pair of actuating units are each configured to apply a torque to the second part in the other sense about the first axis.

21. An actuator assembly according to any preceding claim, wherein the one or more actuating units are configured to tilt the second part relative to the first part about at least one axis perpendicular to a primary axis of the actuator assembly.

22. An actuator assembly according to any preceding claim, wherein the one or more actuating units are configured to move the second part relative to the first part along a primary axis of the actuator assembly.

23. An actuator assembly according to any preceding claim, wherein the one or more actuating units are configured to drive rotation of the second part relative to the first part around a primary axis, and wherein the actuator assembly comprises a mechanism configured to convert the relative rotation driven by the actuating units around the primary axis into a secondary movement of the second part, or of a third part, relative to the first part.

24. An actuator assembly according to any preceding claim, wherein the one or more actuating units comprises a plurality of actuating units arranged such that, for each direction along each axis of a Cartesian coordinate system, there is at least one actuating force with a non-zero component along that direction.

25. An actuator assembly according to any preceding claim, wherein the first part or the second part comprises at least part of a lens and / or an image sensor.

26. An actuator assembly comprising: a first part; a second part that is movable relative to the first part; and one or more actuating units each configured to apply an actuating force capable of moving the second part relative to the first part, wherein at least one of the actuating units comprises: a body portion; an SMA (shape memory alloy) 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; anda 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; wherein the angle between the SMA element and the body portion changes by less than ±7.5° throughout an operating range of movement of the body portion.

27. An actuator assembly comprising: a first part; a second part that is movable relative to the first part; and one or more actuating units each configured to apply an actuating force capable of moving the second part relative to the first part, wherein at least one of the actuating units comprises: a body portion; an SMA (shape memory alloy) 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; wherein the body portion rotates about an effective pivot axis during operation, and the ratio of (a) a lever arm associated with the input force and the effective pivot axis to (b) the length of the SMA element is greater than 0.2.

Images