Actuator assembly

Abstract

An actuator assembly 2 comprises a first support part 10 defining a primary axis P. A second part 100 can be tilted about an axis perpendicular to the primary axis by SMA wires 340 which apply a force

Description

Field The present application relates to an actuator assembly with one or more actuating units, at least one actuating unit including a shape memory alloy (SMA) element, e.g. an SMA wire. Summary According to an aspect of the present invention, there is provided an actuator assembly comprising: a first part, wherein a first primary axis is defined with reference to the first part; a second part that is movable relative to the first part, wherein a second primary axis is defined with reference to the second part; a third part that is movable relative to the second part and the first part; a first group of actuating units configured, on selective actuation, to tilt the second part relative to the first part about a first tilt axis perpendicular to the first primary axis; and a second group of actuating units configured, on selective actuation, to tilt the third part relative to the second part about a second tilt axis perpendicular to the second primary axis; wherein the first and second tilt axes are non-parallel axes. Each actuating unit of the first group of actuating units is configured, on actuation, to apply an actuating force to the second part with a force component which acts in a first direction parallel to the first primary axis, and each actuating unit of the second group of actuating units is configured, on actuation, to apply an actuating force to the third part with a force component which acts in a second direction parallel to the first primary axis; wherein the first and second directions are opposite directions. At least one of the actuating units comprises an SMA (shape memory alloy) element comprising a first end and a second end both coupled to one of the first, second and third parts of the actuator assembly. The first primary axis may be the longitudinal axis of the first part. The first primary axis may be the primary axis and / or longitudinal axis of the actuator assembly. The first primary axis may pass through the first, second and third parts. The second primary axis may be the longitudinal axis of the second part. The second primary axis may pass through the first, second and third parts. The actuator assembly may comprise a third primary axis defined with reference to the third part. The third primary axis may be the longitudinal axis of the third part. The third primary axis may pass through the first, second and third parts. The first part may be a support structure. The second part may be an intermediate part. The third part may be a (e.g. final) movable part. The third part may be a camera module comprising an image sensor and a lens assembly including one or more lenses configured to focus an image on the image sensor. Optionally, the actuator assembly comprises: a first bearing arrangement configured to guide the relative movement between the first and second parts; and wherein the first tilt axis is defined by the first bearing arrangement. Optionally, the actuator assembly comprises: a second bearing arrangement configured to guide the relative movement between the second and third parts; and wherein the second tilt axis is defined by the second bearing arrangement. Optionally, when viewed along the first primary axis, each SMA element of the first group of actuating units generally extends parallel to the first tilt axis, and / or wherein each SMA element of the second group of actuating units generally extends parallel to the second tilt axis. Optionally, the SMA element of one or more of the at least one of the actuating units is generally V-shaped. Optionally, one or more of the at least one of the actuating units actuating units comprises a flexure component coupled to the SMA element, wherein the flexure component is configured to flex on actuation of the SMA element so as to apply the actuating force. Optionally, (i) the first group of actuating units comprises a total of two actuating units; and / or (ii) the second group of actuating units comprises a total of two actuating units. Optionally, the first group of actuating units comprises half (e.g. a first pair) of the actuating units on a first side of the actuator assembly and the other half (e.g. a second pair, not overlapping with the first pair) of the actuating units on a second side of the actuator assembly opposite the first side. Optionally, the second group of actuating units comprises half (e.g. a first pair) of the actuating units on a third side of the actuator assembly and the other half (e.g. a second pair, not overlapping with the first pair) of the actuating units on a fourth side of the actuator assembly opposite the third side. The first and second sides may be different from the third and fourth sides. The first and second sides may be adjacent to the third and fourth sides. The first, second, third and fourth sides may be arranged in a loop around the first primary axis. Optionally, the third part comprises an electronic component. Optionally, the third part comprises one or more lenses and / or an image sensor. Optionally, the SMA elements are SMA wires. The actuator assembly may be a micro-actuator for a camera assembly or a mobile phone. The above-described actuating units may provide optical image stabilisation (OIS) by providing tilting of a camera module comprising a lens assembly and an image sensor. Brief Description of the Drawings Certain embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a schematic cross-sectional view of a camera assembly incorporating an actuator assembly; Figure 2 is a schematic plan view of the actuator assembly; Figure 3 is a schematic perspective view of part of the actuator assembly; Figure 4 is a schematic perspective view the actuator assembly; Figure 5 is a schematic illustration of an actuating unit; Figure 6 is schematic illustration of a bearing arrangement; Figure 7 is a schematic illustration of a bearing arrangement. Detailed Description Camera......assembly Figure 1 schematically shows an apparatus 1 incorporating an actuator assembly 2. The apparatus 1 is a camera assembly 1 in this example. Generally, the camera assembly 1 is to be incorporated in a portable electronic device such as a smartphone. Thus, miniaturisation can be an important design criterion. The actuator assembly 2 includes a support structure 10 (herein also referred to as the first part 10), an intermediate part 100 (herein also referred to as the second part 100), and a movable part 200 (herein also referred to as the third part 200). The intermediate part 100 is movable relative to the support structure 10. The movable part 200 is movable relative to the intermediate part 100 and 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 a first group of actuating units 30 connected between (i.e. connected to) the support structure 10 and the intermediate part 100. The first group of actuating units 30 are arranged to apply actuating forces F between the intermediate part 100 and the support structure 10. Selectively varying these actuating forces F may cause the intermediate part 100 to move relative to the support structure 10. The first group of actuating units 30 are thus capable of driving movement of the intermediate part 100 relative to the support structure 10. The actuator assembly 2 also includes a second group of actuating units 30 connected between (i.e. connected to) the intermediate part 100 and the movable part 200. The second group of actuating units 30 are arranged to apply actuating forces F between the movable part 200 and the intermediate part 100. Selectively varying these actuating forces F may cause the movable part 200 to move relative to the intermediate part 100. The second group of actuating units 30 are thus capable of driving movement of the movable part 200 relative to the intermediate part 100. The movable part 200 is supported on the support structure 10 via the intermediate part 100, and thus configured to move together with the intermediate part 100 when the intermediate part 100 is moved relative to the support structure 10. As such, the first group of actuating units 30 is also capable of moving the movable part 200 relative to the support structure 10 via the intermediate part 100. A first primary axis P is defined with reference to the support structure 10. The first primary axis P extends through the support structure 10, e.g. through the centre of the support structure 10. In some examples, the support structure 10 extends predominantly in a direction perpendicular to the first primary axis P. In other words, the extent of the support structure 10 along the first primary axis P is less than the extent thereof along any direction perpendicular to the first primary axis P. The first primary axis P may be the longitudinal axis of the support structure 10. The first primary axis P may pass through the first, second and third parts 10,100, 200. A second primary axis S is defined with reference to the intermediate part 100 and thus moves (e.g. tilts) together with the intermediate part 100 when the intermediate part 100 is moved (e.g. tilted) relative to the support structure 10. The second primary axis S extends through the intermediate part 100, e.g. through the centre of the intermediate part 100. In some examples, the intermediate part 100 extends predominantly in a direction perpendicular to the second primary axis S. In other words, the extent of the intermediate part 100 along the second primary axis S is less than the extent thereof along any direction perpendicular to the second primary axis S. The second primary axis S may be the longitudinal axis of the intermediate part 100. The second primary axis S may pass through the first, second and third parts 10,100, 200. A third primary axis T is defined with reference to the movable part 200. The third primary axis T thus moves (e.g. tilts) together with the movable part 200 when the movable part 200 is moved (e.g. tilted) relative to the intermediate part 100 (and, thus, also the support structure 10). The third primary axis T extends through the movable part 200, e.g. through the centre of the movable part 200. In some examples, the movable part 200 extends predominantly in a direction perpendicular to the third primary axis T. In other words, the extent of the movable part 200 along the third primary axis T is less than the extent thereof along any direction perpendicular to the third primary axis T. The third primary axis T may be the longitudinal axis of the movable part 200. The third primary axis T may pass through the first, second and third parts 10,100, 200. The movable part 200 (herein also referred to as a camera module 200) comprises an image sensor 220 and a lens assembly 210, including one or more lenses 211, configured to focus an image on the image sensor 220. The lens assembly 210 may include a lens carrier 210, for example in the form of a cylindrical body, supporting the one or more lenses 211. The image sensor 220 is configured to capture 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 1 in which each lens 211 has a diameter of 20mm or less, for example of 12mm or less. The first group of actuating units 30 are configured to, upon selective actuation, tilt (i.e. rotate) the intermediate part 100 (and thus also the movable part 200) relative to the support structure 10 about a first tilt axis x which is perpendicular to the first primary axis P. The second group of actuating units 30 are configured to, upon selective actuation, tilt (i.e. rotate) the movable part 200 relative to the intermediate part 100 (and thus also the support structure 10) about a second tilt axis y which is perpendicular to the second primary axis S. The first and second tilt axes x, y are nonparallel axes. As shown in Figure 2, the first and second tilt axes x, y may be perpendicular to each other when viewed along the primary axis P. The first and second groups of actuating units 30 are capable of providing optical image stabilisation (OIS) by driving such tilting of the camera module 200 relative to the support structure 10. Such OIS functionality is herein also referred to as 'tilt-OIS'. Figures 1 and 2 show the actuator assembly 2 in an untilted configuration wherein the intermediate part 100 is untilted relative to the support structure 10 and the movable part 200 is untilted relative to the intermediate part 100 (and the support structure 10) such that the first, second and third primary axes P, S, T are collinear (i.e. the first, second, and third primary axes P, S, T are parallel and coincide). In other embodiments, the first, second and third primary axes P, S, T may be parallel but may not necessarily coincide when the actuator assembly 2 is in the untilted configuration. As shown in Figure 1, when the actuator assembly 2 is in the untilted configuration, the optical axis O of the lens assembly 210 and the imaging axis of the image sensor 220 may also be collinear with the first, second and third primary axis P, S, T (i.e. the first primary axis P, the second primary axis S, the third primary axis T, the optical axis O, and the imaging axis may be parallel and coincide). In other embodiments, or e.g. wherein the lens assembly 210 has been translated relative to the image sensor 220 in a direction perpendicular to the optical axis O, the first primary axis P, the second primary axis S, the third primary axis T, the optical axis O, and the imaging axis may be parallel to each other but may not necessarily coincide when the actuator assembly 2 is in the untilted configuration. Each actuating unit 30 comprises a shape memory alloy (SMA) wire 34 configured to, upon actuation (i.e. on contraction), be capable of driving relative movement between the parts of the actuator assembly 2 to which the actuating unit 30 is connected to. 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 the SMA wires 34 forming part of the actuating units 30. 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 200. The drive signals are chosen to drive relative movement of the movable part 200 in a desired manner, for example, so as to achieve OIS by stabilizing the image sensed by the image sensor 220. The controller 8 supplies the generated drive signals to the SMA wires 34. 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 200 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. The lens assembly 210 may be movable relative to the image sensor 220 along the optical axis O. Where this is the case, the actuator assembly 2 may comprise one or more further actuating units (not shown) configured to drive such relative movement. Such relative movement has the effect of adjusting the focus of the image on the image sensor 4, i.e. providing auto-focus (AF) functionality. The lens assembly 210 and the image sensor 220 may be movable relative to each other in any direction perpendicular to the optical axis O. This relative movement may be translational and / or rotational (e.g. the image sensor 220 may be rotatable relative to the lens assembly 210 about the optical axis O). Where this is the case, the actuator assembly 2 may comprise one or more further actuating units (not shown) configured to drive such relative movement. Such relative movement has the effect of moving the image on the image sensor 4 and can provide OIS functionality. This variation of OIS is herein also referred to as 'shift-OIS'. The controller 8 may also generate drive signals for these further actuating units. In other words, the controller 8 may also be configured to supply drive signals chosen to drive relative movement between the lens assembly 210 and the image sensor 220 in a desired manner, for example, so as to achieve AF and / or shift-OIS functionality. Alternatively, at least some of the drive signals for these further actuating units may be provided by one or more different controllers. One or more of the further actuating units may be SMA actuating units - i.e. actuating units comprising SMA elements. One or more of the further actuating units may be non-SMA actuating units, e.g. voice coil motor (VCM) actuating units. 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 tilting of a movable part 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. As shown in Figures 3 and 4, the actuator assembly 2 includes a first bearing arrangement 40i, 40? that supports the intermediate part 100 on the support structure 10. The first bearing arrangement 40i, 40? is provided between the intermediate part 100 and the support structure 10. The first bearing arrangement 40i, 40z is configured to allow the intermediate part 100 to tilt about the first tilt axis x relative to the support structure 10. The first bearing arrangement 40i, 4O2 is also configured to constrain, i.e. reduce or prevent, tilting of the intermediate part 100 relative to the support structure 10 about an axis perpendicular to the first tilt axis x and perpendicular to the first primary axis P. The first bearing arrangement 40i, 402 may also be configured to constrain translational movement of the intermediate part 100 relative to the support structure 10 in any direction (or at least one direction) perpendicular to the first primary axis P. The first bearing arrangement 40i, 4O2 may include one or more of the following bearings: a rolling bearing (such as a ball bearing as illustrated in Figure 3), a ball race (as shown in Figure 7), a flexure bearing (i.e. an arrangement of flexures or other resilient elements that guide movement), or a plain (i.e. sliding contact) bearing (such as the one illustrated in Figure 4). Similarly, as shown in Figure 4, the actuator assembly 2 also includes a second bearing arrangement 40s, 404 that supports the movable part 200 on the intermediate part 100. The second bearing arrangement 4O3, 404 is provided between the movable part 200 and the intermediate part 100. The second bearing arrangement 4O3, 404 is configured to allow the movable part 200 to tilt about the second tilt axis y relative to the intermediate part 100. The second bearing arrangement 4O3, 404 is also configured to constrain, i.e. reduce or prevent, tilting of the movable part 200 relative to the intermediate part 100 about an axis perpendicular to the first tilt axis x and perpendicular to the second primary axis S. The second bearing arrangement 40s, 404 may also be configured to constrain translational movement of the movable part 200 relative to the intermediate part 100 in any direction (or at least one direction) perpendicular to the second primary axis S. The second bearing arrangement 4O3, 404 may include one or more of the following bearings: a rolling bearing (such as a ball bearing), a ball race (as shown in Figure 7), a flexure bearing (i.e. an arrangement of flexures or other resilient elements that guide movement), or a plain (i.e. sliding contact) bearing (such as the one illustrated in Figure 4). First stage of the actuator assembly Figure 3 illustrates a 'first tilt stage' of the actuator assembly 2 including the support structure 10, the intermediate part 100, the first group of actuating units 30, and the first bearing arrangement 40i, 402. The term 'first tilt stage' is herein used to refer to the group of components of the actuator assembly 2 which are configured to enable the tilting of the intermediate part 100 relative to the support structure 10 about the first axis x. As shown in Figure 3, the first bearing arrangement 40i, 4O2 includes a first bearing 40i and a second bearing 4O2. The first bearing 40i is located on a first side 2a of the actuator assembly 2 and the second bearing 4O2 is located on a second, opposite side 2b of the actuator assembly 2. The first bearing arrangement 40i, 4O2 (i.e. the first and second bearings 40i, 4O2 thereof) defines the first tilt axis x. The two bearings 40i, 4O2 allow the intermediate part 100 to rotate about the first tilt axis x relative to the support structure 10. Such a rotation is labelled Rx in Figure 3. As shown in Figure 3, the first group of actuating units 30 includes two SMA actuating units 30. Each of these SMA actuating units 30 are connected between the intermediate part 100 and the support structure 10. In particular, each actuating unit 30 comprises an SMA (shape memory alloy) element comprising a first end and a second end both coupled to the support structure 10, and a mid-portion coupled to the intermediate part 100. Each SMA actuating unit 30 provides a downwards force on the intermediate part 100 (i.e. exerts a force on the intermediate part 100 with a component in a downwards direction along the first primary axis P) when the SMA actuating unit 30 is in tension. The downwards force component urges the intermediate part 100 and the support structure 10 towards each other. A first SMA actuating unit 30 is located on a third side 2c of the actuator assembly 2, and a second SMA actuating unit 30 is located on a fourth, opposite side 2d of the actuator assembly 10. The first and second sides 2a, 2b are different from the third and fourth sides 2c, 2d. The first and second sides 2a, 2b are adjacent to the third and fourth sides 2c, 2d. The first, second, third and fourth sides 2a-2d arranged in a loop around the first primary axis P. The first SMA actuating unit 30 generally lies in a first plane parallel to the first primary axis P, and the second SMA actuating unit 30 generally lies in a second plane parallel to the first primary axis P. The first actuating unit 30 may be actuated so as to produce a first, downwards force on a first side of intermediate part 100 (located on the third side 2c of the actuator assembly 2). The second SMA actuating unit 30 may be actuated so as to produce a second, downwards force on a second, opposite side of the intermediate part 100 (located on the fourth side 2d of the actuator assembly 2). When these first and second forces are suitably balanced (e.g. equal), the intermediate part 100 may be held in its untilted position relative to the support structure 10 against the first bearing arrangement 40i, 40? (such that the first and second primary axes P, S are at least parallel to each other). When these first and second forces are unbalanced (e.g. different), the intermediate part 100 tilts relative to the support structure 10 about the first tilt axis x in one sense or another depending on which of the first and second forces are greater. As mentioned above, such a rotation is labelled Rx in Figure 3. Second stage of the actuator assembly The term 'second tilt stage' is herein used to refer to the group of components of the actuator assembly 2 which are configured to enable the tilting of the movable part 200 relative to the intermediate part 100 about the second tilt axis y. The second tilt stage of the actuator assembly 2 includes the intermediate part 100, the movable part 200, the second group of actuating units 30, and the second bearing arrangement 40a, 404. The second tilt stage works in the same manner as the first tilt stage. The second tilt stage may be considered as an upside-down version of the first tilt stage which is arranged to tilt the movable part 200 relative to the intermediate part 100 about the second tilt axis y, rather than to tilt the intermediate part 100 relative to the support structure 10 about the first tilt axis x. The second bearing arrangement 40a, 404 includes a third bearing 40a and a fourth bearing 404. The third bearing 40a is located on the third side 2c of the actuator assembly 2 and the fourth bearing 404 is located on the fourth, opposite side 2d of the actuator assembly 2. The second bearing arrangement 40a, 404 (i.e. the first and second bearings 40i, 40? thereof) defines the second tilt axis y. The two bearings 40a, 404 allow the movable part 200 to rotate about the second tilt axis y relative to the intermediate part 100. Such a rotation may be referred to as rotation Ry. As shown in Figures 2 and 4, the first group of actuating units 30 includes two SMA actuating units 30. Each of these SMA actuating units 30 are connected between the movable part 200 and the intermediate part 100. In particular, each actuating unit 30 comprises an SMA (shape memory alloy) element comprising a first end and a second end both coupled to the intermediate part 100, and a mid-portion coupled to the movable part 200. Each of these SMA actuating units 30 provides a downwards force on the movable part 200 (i.e. exerts a force on the movable part 200 with a component in a downwards direction along the second primary axis S) when the SMA actuating unit 30 is in tension. The downwards force component urges the movable part 200 and the support intermediate part 100 towards each other. A first SMA actuating unit 30 (of the second group of actuating units 30) is located on the first side 2a of the actuator assembly 2, and a second SMA actuating unit 30 (of the second group of actuating units 30) is located on the second, opposite side 2b of the actuator assembly 10. The first SMA actuating unit 30 generally lies in a first plane parallel to the second primary axis S, and the second SMA actuating unit 30 generally lies in a second plane parallel to the second primary axis S. The first SMA actuating unit 30 may be actuated so as to produce a first, upwards force on a first side of movable part 200 (located on the first side 2a of the actuator assembly 2). The second SMA actuating unit 30 may be actuated so as to produce a second, upwards force on a second, opposite side of the movable part 200 (located on the second side 2b of the actuator assembly 2). When these first and second forces are suitably balanced (e.g. equal), the movable part 200 may be held in its untilted position relative to the intermediate part 100 against the second bearing arrangement 40^, 404 (such that the second and third primary axes S, T are at least parallel to each other). When these first and second forces are unbalanced (e.g. different), the movable part 200 tilts relative to the intermediate part 100 about the second tilt axis y in one sense or another depending on which of these first and second forces are greater. An important difference between the first and second tilt stages is that the SMA actuating units 30 of the second tilt stage are configured to provide an upwards force along the second primary axis S (which, as discussed above, corresponds to the first primary axis P when the actuator assembly 2 is in the untilted configuration), instead of a downwards force along the first primary axis P (which, as discussed above, corresponds to the second primary axis S when the actuator assembly 2 is in the untilted configuration). In other words, the first group of actuating units 30 is configured to drive the intermediate part 100 generally downwards against the support structure 10, and the second group of actuating units 30 is configured to pull the movable part 200 generally upwards against the intermediate part 100. This arrangement can be beneficial as e.g. it may allow the movable part 200 to move towards endstops located above and below the movable part 200 during drop events (e.g. in the event that a smartphone comprising the camera assembly 1 is dropped). However, it will be appreciated that such an arrangement is optional. The first and second tilt stages may instead be configured to exert forces that are generally in the same direction (e.g. upwards or downwards) along the first and / or second primary axes P, S. In the examples shown, each of the first group of SMA actuating units 30 comprise an SMA element 340 with a first end and a second end both coupled (e.g. via coupling elements such as crimps) to the support structure 10, and a mid-portion coupled (e.g. via a coupling element 360, such as a crimp) to the intermediate part 100. However, this arrangement may be reversed, with the first group of SMA actuating units 30 comprising an SMA element 340 with a first end and a second end both coupled (e.g. via coupling elements such as crimps) to the intermediate part 100, and a mid-portion coupled (e.g. via a coupling element 360, such as a crimp) to the support structure 10. Similarly, in the examples shown, each of the second group of SMA actuating units 30 comprise an SMA element 340 with a first end and a second end both coupled (e.g. via coupling elements such as crimps) to the intermediate part 100, and a mid-portion coupled (e.g. via a coupling element 360, such as a crimp) to the movable part 200. However, this arrangement may be reversed, with the second group of SMA actuating units 30 comprising an SMA element 340 with a first end and a second end both coupled (e.g. via coupling elements such as crimps) to the movable part 200, and a mid-portion coupled (e.g. via a coupling element 360, such as a crimp) to the intermediate part 100. Applications As discussed above, 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 tilting of a movable part 200 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. The actuator assembly may be used to move at least part of an illumination source in a 3D imaging system such as described in WO2020 / 030916 (which is incorporated by reference to the maximum extent permissible by law). The actuator assembly may be used to move at least part of a light source (e.g. a projector), a display or one or more other optical components of a display system for an augmented reality (AR) system or other electronic device. Other variations It will be appreciated that there may be many other variations of the above-described examples. For example, the actuator assembly 2 may include different types of actuating units to those described above. Examples of such actuating units include the actuating unit shown in Figure 5 which comprises a flexure component 360' coupled to an SMA element 340', wherein the flexure component 360' is configured to flex (e.g. buckle) on actuation of the SMA element 340' so as to apply the actuating force F. Other 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 first part 10 and the second part 100 or connected between the second part 100 and the third part 200. The documents referred to in the preceding sentence are each herein incorporated by reference to the maximum extent permissible by law. The actuator assembly 2 may have any number of different types of actuating units, and may have any suitable number of actuating units of each type. It will be appreciated that at least one of the actuating units 30 may be another type of SMA actuating unit or a non-SMA actuating unit, e.g. a voice coil motor (VCM) actuating unit. It will be appreciated that an actuator assembly comprising only a single tilt stage (e.g. only the first tilt stage) may be used in some cases. For example, a single tilt stage may be used for providing OIS in periscope cameras. It will be appreciated that the first bearing arrangement may not need to be provided in the actuator assembly 2 e.g. wherein the first group of actuating units comprises one or more actuating units which do not require bearings for providing tilting about the first tilt axis x. Similarly, it will be appreciated that the second bearing arrangement may not need to be provided in the actuator assembly 2 e.g. wherein the second group of actuating units comprises one or more actuating units which does not require bearings for providing tilting about the second tilt axis y. As shown in Figure 6, the first bearing arrangement may be configured to allow movement of the intermediate part 100 in directions perpendicular to the primary axis P. Similarly, the second bearing arrangement may be configured to allow movement of the movable part 200 in directions perpendicular to the second primary axis S. SMA 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

1. An actuator assembly comprising:a first part, wherein a first primary axis is defined with reference to the first part;a second part that is movable relative to the first part, wherein a second primary axis is defined with reference to the second part;a third part that is movable relative to the second part and the first part;a first group of actuating units configured, on selective actuation, to tilt the second part relative to the first part about a first tilt axis perpendicular to the first primary axis; anda second group of actuating units configured, on selective actuation, to tilt the third part relative to the second part about a second tilt axis perpendicular to the second primary axis;wherein the first and second tilt axes are non-parallel axes; andwherein each actuating unit of the first group of actuating units is configured, on actuation, to apply an actuating force to the second part with a force component which acts in a first direction parallel to the first primary axis, and each actuating unit of the second group of actuating units is configured, on actuation, to apply an actuating force to the third part with a force component which acts in a second direction parallel to the first primary axis;wherein the first and second directions are opposite directions; andwherein at least one of the actuating units comprises an SMA (shape memory alloy) element comprising a first end and a second end both coupled to one of the first, second and third parts of the actuator assembly.

2. An actuator assembly according claim 1, wherein the actuator assembly comprises: a first bearing arrangement configured to guide the relative movement between the first and second parts; and wherein the first tilt axis is defined by the first bearing arrangement.

3. An actuator assembly according claim 1 or 2, wherein the actuator assembly comprises: a second bearing arrangement configured to guide the relative movement between the second and third parts; and wherein the second tilt axis is defined by the second bearing arrangement.

4. An actuator assembly according to any preceding claim, wherein when viewed along the first primary axis, each SMA element of the first group of actuating units generally extends parallel to thefirst tilt axis, and / or wherein each SMA element of the second group of actuating units generally extends parallel to the second tilt axis.

5. An actuator assembly according to any preceding claim, wherein the SMA element of one or more of the at least one of the actuating units is generally V-shaped.

6. An actuator assembly according to any preceding claim, wherein one or more of the at least one of the actuating units actuating units comprises a flexure component coupled to the SMA element, wherein the flexure component is configured to flex on actuation of the SMA element so as to apply the actuating force.

7. An actuator assembly according to any preceding claim, wherein: (i) the first group of actuating units comprises a total of two actuating units; and / or (ii) the second group of actuating units comprises a total of two actuating units.

8. An actuator assembly according to any preceding claim, wherein the first group of actuating units comprises half of the actuating units on a first side of the actuator assembly and the other half of the actuating units on a second side of the actuator assembly opposite the first side; and / or the second group of actuating units comprises half of the actuating units on a third side of the actuator assembly and the other half of the actuating units on a fourth side of the actuator assembly opposite the third side.

9. An actuator assembly according to any preceding claim, wherein the third part comprises an electronic component.

10. An actuator assembly according to any preceding claim, wherein the third part comprises one or more lenses and / or an image sensor.

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