Actuator assembly

Abstract

An actuator assembly (1) comprises a support structure (100), with a first primary axis (Zl) defined with reference to the support structure, an intermediate part (200) that is movable relative to the support structure, with a second primary axis (Z2) defined with reference to the intermediate part, and a movable part (300) that is movable relative to the intermediate part and the support structure. One or more tilt actuating units each configured to apply an actuating force capable of tilting the movable part relative to the support structure about a first tilt axis perpendicular to the first primary axis and / or a second tilt axis perpendicular to the second primary axis, wherein the first and second tilt axes are non-parallel axes. The assembly also has one or more endstops (260, 310) which are configured, upon engagement, to limit axial translation of the movable part relative to the support structure along the first primary axis, and wherein the intermediate part is configured to elastically deform to allow the one or more endstops to engage.

Description

[0001] ACTUATOR ASSEMBLY

[0002] Field

[0003] The present application relates to an actuator assembly comprising a support structure, a movable part tiltable relative to the support structure, and an intermediate part (e.g. a gimbal component) provided to allow the tilting of the movable part.

[0004] Summary

[0005] According to a first aspect of the present disclosure, there is provided an actuator assembly comprising: a support structure, with a first primary axis defined with reference to the support structure; an intermediate part that is movable relative to the support structure, with a second primary axis defined with reference to the intermediate part; a movable part that is movable relative to the intermediate part and the support structure; one or more tilt actuating units each configured to apply an actuating force capable of tilting the movable part relative to the support structure about a first tilt axis perpendicular to the first primary axis and / or a second tilt axis perpendicular to the second primary axis, wherein the first and second tilt axes are non-parallel axes; and one or more endstops configured, upon engagement, to limit axial translation of the movable part relative to the support structure along the first primary axis; and wherein the intermediate part is configured to elastically deform to allow the one or more endstops to engage.

[0006] The one or more endstops may be configured to prevent the intermediate part from undergoing plastic deformation.

[0007] The actuating units may be configured to be capable of not causing the one or more endstops to engage when the movable part is only subject to forces exerted by the actuating units, in addition to a gravitational force equivalent of lg (i.e. "g-force" or the force an object is subject to when it is at rest on Earth's surface).

[0008] When the movable part is only subject to forces exerted by the actuating units and a g-force of lg, the intermediate part may be configured to not be able to elastically deform along the first primary axis by more than 5%, more than 10%, more than 20%, more than 30%, more than 40% or more than 50% of the amount of elastic deformation that the intermediate part has to undergo along the first primary axis to allow the one or more endstops to engage. For example, if the intermediate part is configured to undergo 5mm of elastic deformation along the first primary axis to reach an endstop, the maximum amount of elastic deformation the intermediate part can undergo along the first primary axis may be 0.25mm (5% of 5mm), 0.5mm (10% of 5mm), 1mm (20% of 5mm), 1.5mm (30% of 5mm), 2mm (40% of 5mm), or 2.5mm (50% of 5mm) towards the endstop, when the movable part is only subject to forces exerted by the actuating units and a g- force of 1g.

[0009] Each endstop may comprise an endstop surface of the movable part and an endstop surface of the support structure, wherein the endstop surfaces of the movable part and an endstop surface of the support structure are configured to engage each other upon engagement of the one or more endstops.

[0010] The intermediate part may be mounted on the support structure, and the movable part may be mounted on the intermediate part.

[0011] The actuator assembly may comprise one or more tethering features configured to hold the intermediate part and the support structure together.

[0012] The actuator assembly may comprise one or more tethering features configured to hold the intermediate part and the movable part together.

[0013] At least one of the tilt actuating units may be configured to apply an actuating force capable of rotating the movable part relative to the support structure about the first and / or second primary axes.

[0014] The actuator assembly may comprise one or more rotation actuating units configured to apply an actuating force capable of rotating the movable part relative to the support structure about the first and / or second primary axes.

[0015] None of the one or more rotation actuating units may be a subset of the one or more tilt actuating units.

[0016] At least one of the actuating units (i.e. at least one of the tilt actuating units and / or the rotation actuating units) may comprise an SMA (shape memory alloy) element configured, on actuation, to give rise to the actuating force (i.e. the actuating force the at least one of the actuating units is configured to apply).

[0017] At least one of the actuating units (i.e. at least one of the tilt actuating units and / or the rotation actuating units) may comprise: a body portion; a shape memory alloy (SMA) element connected between the body portion and one of the support structure, the intermediate part, and the movable part, and configured, on actuation, to apply an input force to the body portion; and a forcemodifying element connected between the body portion and the one of the support structure, the intermediate part, and the movable part, and configured to modify the input force so as to give rise to the actuating force (i.e. the actuating force the at least one of the actuating units is configured to apply).

[0018] The actuator assembly may comprise a first bearing arrangement configured to allow tilting of the intermediate part (and the movable part) relative to the support structure about the first tilt axis, and to constrain tilting of the intermediate part relative to the support structure about the second tilt axis or an axis parallel to the second tilt axis.

[0019] The first bearing arrangement may be configured to allow rotation of the intermediate part (and the movable part) relative to the support structure about the first primary axis.

[0020] The actuator assembly may comprise a second bearing arrangement configured to allow tilting of the movable part relative to the intermediate part about the second tilt axis, and to constrain tilting of the movable part relative to the intermediate part about the first tilt axis or an axis parallel to the first tilt axis.

[0021] The second bearing arrangement may be configured to allow rotation of the movable part relative to the intermediate part about the second primary axis.

[0022] Each of the one or more tilt actuating units may be configured to exert a force on the movable part and / or the intermediate part with a component in a first direction along the first primary axis.

[0023] The one or more tilt actuating units may comprise: a first and a second actuating unit configured to tilt the movable part and the intermediate part relative to the support structure about the first tilt axis; and a third and a fourth actuating unit configured to tilt the movable part relative to the intermediate part and the support structure about the second tilt axis.

[0024] The first and second actuating units may be each configured to exert a force on the movable part and / or the intermediate part with a component in a first direction along the first primary axis, and the third and fourth actuating units are each configured to exert a force on the movable part with a component in a second opposite direction along the first primary axis. In other words, all tilt actuating units are configured to exert forces on the movable part and / or the intermediate part in generally the same direction along the first primary axis.

[0025] Each tilt actuating unit may be configured to apply the / its actuating force to the movable part.

[0026] The movable part may comprise an electronic component. The electronic component may be an image sensor. The electronic component may also be an emitter, a display, or a part thereof.

[0027] The movable part may comprise one or more lenses and / or an image sensor.

[0028] The movable part may comprise an image sensor and a lens assembly configured to focus an image on the image sensor.

[0029] Brief description of the drawings

[0030] Certain embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which:

[0031] Figure 1 is a schematic perspective view of an actuator assembly comprising a movable part;

[0032] Figure 2 is a schematic perspective exploded-view of the actuator assembly of Figure 1;

[0033] Figure 3 is a schematic cross section through the actuator assembly of Figure 1 along the line Ill-Ill of Figure 1 with the movable part in a first position;

[0034] Figure 4 is a schematic cross section through the actuator assembly of Figure 1 along the line Ill-Ill of Figure 1 with the movable part in a second position; Figure 5 is a schematic cross section through the actuator assembly of Figure 1 along the line Ill-Ill of Figure 1 with the movable part in a third position;

[0035] Figure 6 is a schematic cross section through the actuator assembly of Figure 1 along the line Ill-Ill of Figure 1 with the movable part in a fourth position;

[0036] Figure 7 is another schematic representation of the actuator assembly 1 to assist in understanding the operation of the actuating units of the actuator assembly;

[0037] Figures 8A and 8B are perspective and plan views of an actuating unit forming part of the actuator assembly, and Figure 8C is a plan view of another such actuating unit;

[0038] Figure 9 is a schematic plan view of an arrangement of four actuating units; and

[0039] Figure 10 is a schematic perspective view of an arrangement of eight actuating units.

[0040] Detailed description

[0041] As illustrated in Figures 1 and 2, according to a first aspect of the disclosure, there is provided an actuator assembly 1 comprising: a support structure 100, with a first primary axis Z1 defined with reference to the support structure 100; an intermediate part 200 (e.g. a gimbal component 200) that is movable relative to the support structure 100, with a second primary axis Z2 defined with reference to the intermediate part 200; a movable part 300 that is movable relative to the intermediate part 200 and the support structure 100.

[0042] One or more tilt actuating units (not shown in Figures 1 and 2) may be provided and configured to apply an actuating force capable of tilting the movable part 300 relative to the support structure 100 about a first tilt axis X perpendicular to the first primary axis Z1 and / or a second tilt axis Y perpendicular to the second primary axis Z2. The first and second tilt axes X, Y are non-parallel axes.

[0043] The actuator assembly 1 also comprises one or more endstops 250, 310 comprising respective endstop surfaces 122, 250, 320 which are configured, upon engagement, to limit axial translation of the movable part 300 relative to the support structure 100 along the first primary axis Zl.

[0044] The intermediate part 200 is configured to elastically deform to allow the one or more endstops 260, 310 to engage (each other). This will be discussed in further detail below.

[0045] Movable Part

[0046] In the embodiment described herein, the movable part 300 has a rectangular structure with laterally extending endstop elements 330 from each side 340 of the rectangular structure. Each of the endstop elements 330 define a lower endstop surface 320 and an upper endstops surface 370.

[0047] The moveable part 300 may be constructed of a plastics material, but other materials could be used depending upon the application of the actuator assembly 1.

[0048] Support structure

[0049] The support structure 100 has a rectangular structure arranged to accommodate and retain therein the intermediate part 200 and the support structure 100. The support structure 100 includes recessed portions 110 in each side 130 of the support structure 100 and which define respective recess surfaces 120 on two of opposing sides as can be seen in Figure 2. The recess surfaces 120 are configured to engage with the underside of raised portions 270 of the intermediate part 200 opposite endstop surfaces 250. The other two opposing recessed portions 110 define a recess surface comprising a lower endstop surface 122. The sides 130 have internal faces 160 which define an internal cavity 140 into which the movable part 300 and the intermediate part 200 are located.

[0050] As with the moveable part 300, the support structure 100 may also be constructed of a plastics material, but other materials could be used depending upon the application of the actuator assembly 1.

[0051] Intermediate part

[0052] The intermediate part 200 has a frame structure arranged to be located within the internal cavity 140 of the support structure 100.

[0053] The intermediate part 200 includes four clips 230: one centrally located on each side 240 of the intermediate part 200. The clips 230 engage with respective notches 150, 350 on the support structure 100 and movable part 300 to form tethers 210, 220 which connect the intermediate part 200 to both the support structure 100 and the moveable part 300. As shown in Figures 1 and 2 a first pair of tethers 210 connect the intermediate part 200 to the support structure 100 and a second pair of tethers 220 connect the intermediate part 200 to the movable part 300. In the example shown in Figures 1 and 2, the first pair of tethers 210 are located at opposing points along the X axis, whilst the second pair of tethers 220 are located at opposing points along the Y axis.

[0054] This tethering ensures that the intermediate part does not become dislodged in shock scenarios, for example when the actuator assembly 1 is dropped.

[0055] The intermediate part 200 includes raised portions 270 which include a lip portion that extends laterally of the intermediate part and which is configured to engage and match with the recess surfaces 120 of the support structure 100 and which define endstop surfaces 250. The endstop surfaces 250 are configured to engage with respective lower endstop surfaces 320 of the movable part 300 to define the endstop 260 as will be described in further detail below.

[0056] The intermediate part 200 may be constructed from a compliant sprung metal such as high strength stainless steel or a copper alloy such as Beryllium Copper or Titanium Copper. The use of such a material ensures that the intermediate part 200 is stiff enough to support the moveable part 300 during normal operation, but compliant enough to elastically deform under shock inertial loads to the point where the moveable part 300 engages with the endstop surfaces 120 of the support structure 100 before deflecting sections of the intermediate part 200 engage with the support structure 100.

[0057] To prevent the intermediate part 200 from exceeding the yield stress, the intermediate part 200 may be formed from a high strength metal and the shape of the component configured to minimise stress concentrations appropriately whilst maintaining the level of stiffness required for correct operation of the actuator assembly 1. This might include maintaining a resonant frequency mode above a critical level or ensuring the actuating units are configured so to not create problematic deformations when powered on.

[0058] Bearing arrangements

[0059] The actuator assembly 1 comprises one or more bearing arrangements 600. These are illustrated schematically in Figure 7. A first bearing arrangement may be configured to allow tilting of the intermediate part 200 (and the movable part 300) relative to the support structure 100 about the first tilt axis X, and to constrain tilting of the intermediate part 200 relative to the support structure 100 about the second tilt axis Y or an axis parallel to the second tilt axis Y.

[0060] The first bearing arrangement may be configured to allow rotation of the intermediate part 200 (and the movable part 300) relative to the support structure 100 about the first primary axis Zl.

[0061] The actuator assembly 1 may comprise a second bearing arrangement configured to allow tilting of the moveable part 300 relative to the intermediate part 200 about the second tilt axis Y, and to constrain tilting of the movable part 300 relative to the intermediate part 200 about the first tilt axis X or an axis parallel to the first tilt axis X.

[0062] The second bearing arrangement may be configured to allow rotation of the movable part 300 relative to the intermediate part 200 about the second primary axis Z2.

[0063] The bearing arrangements 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.

[0064] The loads that the bearing arrangements 600 experience are limited to the force required to deform the compliant intermediate component which is several orders of magnitude less than if the bearing were to resist the inertial load of the moving part directly in a typical drop test.

[0065] Actuating units

[0066] The actuator assembly 1 comprises one or more tilt actuating units 400 provided and configured to apply an actuating force capable of tilting the movable part 300 relative to the support structure 100 about the first tilt axis X perpendicular to the first primary axis Zl and / or the second tilt axis Y perpendicular to the second primary axis Z2. The first and second tilt axes X, Y are non-parallel axes.

[0067] At least one of the tilt actuating units 400 may be configured to apply an actuating force capable of rotating the movable part 300 relative to the support structure 100 about the first and / or second primary axes Zl, Z2. Alternatively, the actuator assembly 1 may comprise one or more rotation actuating units 500 configured to apply an actuating force capable of rotating the movable part 300 relative to the support structure 100 about the first and / or second primary axis Zl, Z2. None of the one or more rotation actuating units 500 may be a subset of the one or more tilt actuating units.

[0068] At least one of the actuating units (i.e. at least one of the tilt actuating units 400 and / or the rotation actuating units 500) comprises a shape memory allow (SMA) element configured, on actuation, to give rise to the actuating force (i.e. the actuating force the at least one of the actuating units is configured to apply).

[0069] It will be appreciated that at least one of the actuating units 400, 500 may be, for example, a VCM (voice coil motor) actuating unit or a piezoelectric actuating unit.

[0070] Operation of the actuator assembly

[0071] Figure 3 shows the intermediate part 200 in its non-deformed state. In this state, the movable part 300 is at a first (non-tilted) position relative to the support structure 100. In this first position, the distance D3 between the movable part 300 and an upper endstop surface of the support structure 100 (not shown) along the first primary axis Zl is at a maximum. In this first position, the distance DI between the movable part 300 and the lower endstop surface 122 of the support structure 100 along the first primary axis DI is at a maximum. In this first position, the distance D2 between the intermediate part 200 and the support structure 100 along the first primary axis Zl is at a maximum.

[0072] During operation, the intermediate part 200 bears against the support structure 100 and the movable part 300 bears on the intermediate part 200. This bearing action is provided by the bearing arrangements 600 which may comprise contact features integrated into either of the components making contact or could be made via a third component already mentioned.

[0073] The actuating units 400 / 500 and / or the bearing arrangement 600 may constrain, i.e. reduce or prevent, other degrees of freedom of movement of the movable part 300 relative to the support structure 100. The loads that the bearings 600 experience are limited to the force required to deform the compliant intermediate part 200 which is several orders of magnitude less than if the bearing were to resist the inertial load of the moving part directly in a typical drop test. When using free rolling ball bearings or rollers, the tethers 210, 220 ensure they cannot become free in shock scenarios.

[0074] The actuating units 400 / 500 and the bearing arrangement 600 may together support the movable part 300 on the support structure 10.

[0075] As shown in Figure 4, during a drop event (e.g. when a smartphone comprising the actuator assembly 1 is dropped), the intermediate part 200 may elastically deform so that the movable part 300 engages the lower endstop surface 122 of the support structure 100 (so that distance DI = 0). The endstop surfaces 250, 320, 122 are configured such that, when this happens, the intermediate part 200 does not engage the support structure 100 (i.e. distance D2 does not reach 0).

[0076] As shown in Figure 5 and 6, when external forces exerted on the movable part 300 are not significantly large (e.g. when the above-mentioned smartphone is only subject to regular handshake movement from the smartphone user), the intermediate part 200 is configured to elastically deform but this deformation is not large enough to have the endstop surfaces 122, 320 engage each other, i.e. the deformation is not large enough to have the movable part 300 engage the lower and upper endstop surfaces of the support structure 100 (i.e. distance DI and D3 do not reach 0).

[0077] The actuating units 400, 500 may be configured to be capable of not causing the one or more endstops 260, 310 to engage when the movable part 300 is only subject to forces exerted by the actuating units 400 / 500, in addition to a g-force of lg (i.e. the force an object is subject to when it is at rest on Earth's surface).

[0078] Optionally, when the movable part 300 is only subject to forces exerted by the actuating units 400, 500 and a g-force of lg, the intermediate part 200 is configured to not be able to elastically deform along the first primary axis Z1 by more than 5%, 10%, 20%, 30%, 40% or 50% of the amount of elastic deformation that the intermediate part 200 has to undergo along the first primary axis Z1 to allow the one or more endstops 122. 350, 320 to engage (each other).

[0079] For example, if the intermediate part 200 is configured to undergo 5mm of elastic deformation along the first primary axis Z1 to cause the one or more endstops to engage, the maximum amount of elastic deformation the intermediate part 200 can undergo along the first primary axis Z1 may be 0.25mm (5% of 5mm), 0.5mm (10% of 5mm), 1mm (20% of 5mm), 1.5mm (30% of 5mm), 2mm (40% of 5mm), or 2.5mm (50% of 5mm) when the movable part 300 is only subject to forces exerted by the actuating units and a force of 1G.

[0080] Figure 7 is another schematic representation of the actuator assembly 1 to assist in understanding the operation of the actuating units 400, 500.

[0081] In general, in actuator assemblies, the movable part 300 may be movable relative to the support structure 100 with up to six degrees of freedom (DOFs). In the context of describing the DOFs of movement, the primary axis Zl, Z2 may also be referred to as the z axis, and two further axes that are perpendicular to the primary axis Zl, Z2 and to each other may be referred to as the x and y axes. The movable part 300 may be movable relative to the support structure 10 in all or in any subset (including only one) of the following DOFs:

[0082] Tx and Ty: Translational movement in the x-y plane. In other words, the movable part 300 may be independently movable along the x and y axes. The movable part 300 may be movable to any position in the x-y plane within a range of movement. Instead of such planar movement, the movable part 300 may be movable linearly, e.g. along the x or y axis.

[0083] Rx and Ry: Rotational movement (or simply rotation or tilting) about the x and y axes. In other words, the movable part 300 may be rotated about any line perpendicular to the primary axis P. The movable part 300 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 300 may be rotatable about a single axis, e.g. about the x or y axis.

[0084] Tz: Translational movement along the z axis. The movable part 300 may be movable to any translational position along the z axis within a range of movement.

[0085] Rz: Rotational movement (or simply rotation) about the z axis. The movable part 300 may be rotatable to any rotational position (i.e. to any orientation) within a range of movement.

[0086] In some examples, the movable part 300 may be supported, e.g. by the bearing arrangement 600, 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 the bearing arrangement 600 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 WO 2017 / 072525 Al, each of which is herein incorporated by reference.

[0087] In some examples, the movable part 300 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 600, 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. Alternatively, such support may be provided exclusively by the actuating units 400 / 500, similarly to WO 2011 / 104518 Al which discloses an actuator assembly with 8 SMA wires connected between the support structure 10 and the movable part 300. WO 2011 / 104518 Al is herein incorporated by reference.

[0088] Figure 8A shows a perspective view of an example of the actuating unit 400, 500. Figure 8B shows part of the actuating unit 400, 500 in plan view.

[0089] A single actuating unit 400 is shown in Figures 8A and 8B, but it will be appreciated that the actuator assembly 1 generally has multiple actuating units 400, 500 each of which may include the same components described with reference to Figures 8A and 8B.

[0090] The actuating unit 400 includes a body portion 401 to which several other components of the actuating unit 400 are connected as described below. Typically, the body portion 401 is relatively rigid compared to the other components of the actuating unit and does not deform significantly on actuation of the actuating unit 400. In some examples, the body portion 401 is not a distinct part of the actuating unit 400. For example, the body portion 401 may be defined as part of one of the other components of the actuating unit 400 or simply as a connection point between other components of the actuating unit 400.

[0091] The actuating unit 400 also includes a force-modifying flexure 402. The force-modifying flexure 402 is connected between the body portion 401 and the support structure 100. One end of the forcemodifying flexure 402 is connected to the body portion 401. The other end of the force-modifying flexure 402 is connected to the support structure 100, e.g. via a foot portion 406. The foot portion 406 is fixed relative to the support structure 10. In the depicted design, the force-modifying flexure 402 is formed integrally with the foot portion 406 and with the body portion 41, for example from a single sheet of material (such as metal). The force-modifying flexure 402 allows the body portion

[0092] 401 to pivot relative to the support structure 100 about an effective pivot point P. Although the effective pivot point P is shown in Figure 8B as being positioned in the middle of force-modifying flexure 402, the effective pivot point P may have a different position and also need not lie on the force-modifying flexure 402. Such pivotal movement of the body portion 401 relative to the support structure 10 is initially in a direction that is substantially perpendicular to the force-modifying flexure 402.

[0093] The actuating unit 400 also includes an SMA element 404. In this example, the SMA element 404 is an SMA wire 404. The SMA wire 404 is connected between the body portion 401 and the support structure 100. One end of the SMA wire 404 is connected to the support structure 100, e.g. by a crimp 415. The other end of the SMA wire 404 is connected to the body portion 401, e.g. by a crimp 405.

[0094] The actuating unit 400 also includes a coupling link 403. In this example, the coupling link 403 is a coupling flexure 403. The coupling flexure 403 is connected between the body portion 401 and the movable part 300. One end of the coupling flexure 403 is connected to the body portion 401. The other end of the coupling flexure 403 is connected to the movable part 300. The coupling link 403 transfers or transmits an actuating force F from the body portion 401 to the movable part 300. The coupling link 403 is compliant (i.e. deformable) in a direction (or in multiple directions) perpendicular to the actuating force F. This allows the movable part 300 to move in directions other than the direction of the coupling flexure 403 and actuating force F. This can be needed, for example, where different actuating units 30 cause the movable part 300 to move in different directions.

[0095] In this example, the body portion 401, the force-modifying flexure 402, the coupling flexure 403 and the foot portion 406 are integrally formed, for example from a single sheet of material (such as metal). In other examples, one or more or these features, if present, may be formed from different parts or materials.

[0096] The SMA wire 404 is arranged, on contraction, to apply an input force Fi on the body portion 401. The input force Fi acts parallel to the length of the SMA wire 404. The force-modifying flexure

[0097] 402 and the body portion 401 are arranged to modify the input force Fi so as to give rise to the actuating force F, which is transmitted from the body portion 401 to the movable part 300 by the coupling flexure 403. In particular, the input force Fi deforms the force-modifying flexure 402, thereby causing the body portion 401 to pivot about the effective pivot point P. In simple terms, the force-modifying flexure 402 and the body portion 401 act like a lever. The force-modifying flexure 402 and the body portion 401 may modify the direction and / or the magnitude of the input force Fi so as to give rise to the actuating force F.

[0098] In the example illustrated in Figures 8A and 8B, the coupling flexure 403 is at an angle of 90° relative to the SMA wire 404. Also, in this example, the force-modifying flexure 402 is arranged at an angle a of 30° relative to the SMA wire 404, and the force-modifying flexure 402 is placed in tension on contraction of the SMA wire 404. Hence, on contraction of the SMA wire 404 and on resulting deformation of the force-modifying flexure 32, the body portion 401 initially moves at an angle of 60° (90°-a) relative to the length of the SMA wire 404. Thus, it will be appreciated that, in this example, the force is de-amplified and the stroke is amplified, while the direction of the forces / movements is changed by an angle of 90°.

[0099] More generally, the change in direction of the force depends on the angle between the SMA wire 404 and the coupling flexure 403. Also more generally, the change in magnitude of the force is dependent on the ratio of i) the distance Ds from the effective pivot point P to the line on which the SMA wire 404 lies and ii) the distance De from the effective pivot point P to the line on which the coupling flexure 403 lies. In particular, F / Fi is proportional to Ds / Dc. If the SMA wire 404 lies on a line that is closer to the effective pivot point P than the line on which the coupling flexure 403 lies, then the input force Fi is de-amplified. At the same time, the movement of the movable part 300 is amplified, i.e. increased relative to a change in length of the SMA wire 404. Alternatively, if the SMA wire 404 lies on a line that is further away from the effective pivot point P than the line on which the coupling flexure 403 lies, then the input force Fi is amplified. At the same time, the movement of the movable part 300 is de-amplified, i.e. decreased relative to a change in length of the SMA wire 404. The actuating unit 400 can thus be configured to amplify movement or to amplify force due to contraction of the SMA wire 404. The actuating unit 400 can also be configured to change the direction of the input force Fi. In some examples, the actuating unit 400 is configured to change the direction of the input force Fi without changing the magnitude of the force or movement.

[0100] The ratio Ds / Dc is dependent on the location of the end of the SMA wire 404 that is connected to the body portion 401, and on the location of the end of the coupling flexure 403 that is connected to the body portion 401. By way of example, the distance De could be increased by connecting the coupling flexure 403 further to the left of body portion 401 shown in Figure 3B, thereby decreasing Ds / Dc and so increasing the amount of stroke amplification. The ratio Ds / Dc is also dependent on the orientation of the SMA wire 404, and on the orientation of the coupling flexure 403. Such orientations can be defined with reference to the force-modifying flexure 32 (as above) or any suitable reference line. By way of example, the distance Ds could be decreased by angling the SMA wire 404 shown in Figure 8B so that it passes closer to the effective pivot point P, thereby decreasing Ds / Dc and so increasing the amount of stroke amplification. In summary, the amount by which the force-modifying flexure 32 amplifies or de-amplifies the force / stroke of the SMA wire 404 may be tailored by: adjusting the orientation of the SMA wire 404 (and thus of the input force Fi); adjusting the location of the connection point between the SMA wire 404 and the body portion 401 (and thus the location at which the input force Fi acts on the body portion 401); adjusting the orientation of the coupling flexure 403 (and thus of the actuating force F); and / or adjusting the location of the connection point between the coupling flexure 403 and the body portion 401 (and thus the location from which the body portion 401 applies the actuating force F).

[0101] In some examples, at least one actuating unit 400 (preferably each actuating unit 400) is configured such that the force-modifying flexure 32 and the body portion 401 amplifies an amount of contraction of the SMA wire 404. Such amplification, for example, may be by a factor greater than 1.5, preferably greater than 2, further preferably greater than 3. For this purpose, in the example illustrated in Figures 3A and 3B, the angle a between the SMA wire 404 and the force-modifying flexure 32 may be in the range from 0 to 45 degrees, preferably from 13 to 40 degrees. However, in general, the angle a may have other values and the connection points of the SMA wire 404 and / or coupling flexure 403 to the body portion 401 may be adjusted to achieve a desired amount of amplification. As described above, in the example illustrated in Figures 3A and 3B, the coupling flexure 403 is at an angle of about 90 degrees relative to the SMA wire 404. This allows the actuating unit 400 to fold around a corner of the movable part 300 in a compact manner. The angle between the coupling flexure 403 and the SMA wire 404 may be in the range from 70 to 110 degrees, preferably from 80 to 100 degrees. However, in general, the angle between coupling flexure 403 and SMA wire 404 may be outside these ranges.

[0102] For instance, in the actuating unit 400 illustrated in Figure 3C, the force-modifying flexure 402, the coupling flexure 403 and the SMA wire 404 are substantially parallel to one another.

[0103] In the above-described examples, the actuating unit 400 is arranged in a plane. In particular, the SMA wire 404, the coupling flexure 403 and the force-modifying flexure 402 are arranged so as to substantially extend in a common plane, at least when the actuator assembly 2 is in an initial configuration. This allows for a compact configuration of the actuating unit 400. The body portion 401, when embodied by a plate, may further be arranged to extend in the plane. However, in general, the components of the actuating unit 400 need not be arranged in a common plane. The SMA wire 404 and / or the coupling flexure 403 may be angled relative to the plane, for example.

[0104] In the above-described examples, the force-modifying flexure 402 is placed in tension on contraction of the SMA wire 404. This reduces the risk of buckling of the force-modifying flexure 402, reducing the risk of damage to the actuator assembly 1 and making the actuator assembly 1 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 404. With reference to Figure 8B, for example, the force-modifying flexure 402 could extend to the bottom-right from the connection point between the body portion 401 and the force-modifying flexure 402, and so be placed under compression on contraction of the SMA wire 404. An arrangement in which the force-modifying flexure 402 is placed under compression is disclosed in WO 2022 / 084699 Al, which is herein incorporated by reference.

[0105] In the above-described examples, the force-modifying flexure 42 and the SMA wire 404 connect at one end to the support structure 100, and the coupling flexure 403 connects at one end to the movable part 300. In general, this arrangement may also be reversed, with the force-modifying flexure 42 and the SMA wire 404 connecting at one end to the movable part 300, and the coupling flexure 403 connecting at one end to the support structure 100. In the above-described examples, the actuating unit 400 includes a coupling link 403 in the form of a coupling flexure 403. The purpose of the coupling link 403 is to allow movement of the movable part 20 in directions perpendicular to the actuating force F. In general, however, the actuating unit 400 need not include a coupling link 403, e.g. in examples in which there is no movement of the movable part 300 in directions perpendicular to the actuating force F. Furthermore, the coupling link 403 may be embodied by components other than the coupling flexure 403, for example by a ball bearing or plain bearing configured to transmit the actuating force F to the movable part 300 while allowing movement of the movable part 20 in directions perpendicular to the actuating force F. Such alternative examples of the coupling link 403 are disclosed in WO 2022 / 084699 Al. The coupling link 403 may (or may not) be formed by an SMA wire, which may (or may not) be integral with the SMA wire 404 and may (or may not) be driven together with the SMA wire 404.

[0106] Furthermore, instead of the force-modifying flexure 402, the actuator assembly 1 may include a different type of force-modifying element configured to enable the above-described movement of the body portion 401 relative to the support structure 100. Such a force-modifying element may include, for instance, a rigid member with one end connected to the support structure 100 via a suitable pivoting connection (e.g. a pin joint) and the other end connected to the body portion 401.

[0107] Figures 8 and 9 schematically shows a plan view of an example of the actuator assembly 1, showing an arrangement of four actuating units 400. The four actuating units 400 may apply actuating forces F between the movable part 300 and the support structure 100. The actuating forces F are applied to the movable part 300 relative to the support structure 100.

[0108] The four actuating units 400 of Figure 9 are in an arrangement capable of applying actuating forces F so as to move the movable part 300 relative to the support structure 100 to any position within a range of movement.

[0109] In particular, two actuating units 400 (e.g. the top and bottom actuating units in Figure 9) 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 left and right actuating units in Figure 9) 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 400, the movable part 300 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 400 allows the tension in the SMA wires 400 of the respective actuating units 400 to be controlled, allowing for more accurate and reliable positioning of the movable part 20 compared to a situation in which actuating units 400 do not oppose each other.

[0110] In some examples, none of the actuating forces F are collinear. This allows the arrangement of actuating units 400 to translationally move the movable part 300 without applying any net torque to the movable part 300. So, the movable part 300 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 400 is capable of accurately controlling a torque or moment of the movable part 20 about the primary axis Zl, Z2. So, the actuating units 400 are capable of rotating (or not rotating) the movable part 20 relative to the support structure about the primary axis Zl, Z2.

[0111] In particular, two actuating units 400 (e.g. the top and bottom actuating units in Figure 4) are arranged to apply actuating forces F so as to generate a torque or moment between the movable part 300 and the support structure 100 in a first sense (e.g. clockwise) around the primary axis Zl, Z2. The other two actuating units 400 (e.g. the left and right actuating units 400 in Figure 4) are arranged to apply actuating forces F so as to generate a torque or moment between the movable part 20 and the support structure 100 in a second, opposite sense (e.g. anti-clockwise) around the primary axis Zl, Z2. This allows the movable part 300 to be rotated by simultaneously increasing or decreasing the tension of SMA wires in any of the two actuating units 400.

[0112] As shown, two actuating units 400 may be arranged to apply actuating forces F in a corner of the actuator assembly 1. The other two actuating units 400 may be arranged to apply actuating forces F in another, opposite corner of the actuator assembly 1. The actuator assembly 1, and in particular the movable part 20 and / or the support structure 100, may have a square or rectangular footprint. Each actuating unit 400 may be provided on one of the four sides of the actuator assembly 2. In particular, each actuating unit 400 may bend around a corner of the movable part 300 such that the SMA wire 404 and the coupling flexure 403 of each actuating unit 400 extend along adjacent edges of the movable part 300. So, the actuating unit 400 may be as configured in Figures 3A and 3B, for example. The four SMA wires 404 of the four actuating units 400 may extend along the four different edges of the movable part 300. The arrangement of actuating forces F applied between movable part 300 and support structure 100 corresponds to the arrangement of SMA wires 400 described in WO2013 / 175197 Al, which is herein incorporated by reference.

[0113] In this example, the actuating forces F are perpendicular to the primary axis Zl, Z2, 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 Zl, Z2. This component along the primary axis Zl, Z2 may be resisted by the bearing arrangement 600, 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 Zl, Z2, for example so as to load plain or rolling bearings arranged between the movable part 300 and the support structure 100.

[0114] Although, for illustrative purposes, the arrangement of actuating units 400 was described as moving the movable part 300 in the movement plane (e.g. translationally along the x and y axis, or rotationally about the primary axis Zl, Z2), in other examples the movable part 20 may be moved differently. For example, the same arrangement of actuating forces F may be used to tilt the movable part 300 relative to the support structure 100 about axes perpendicular to the primary axis Zl, Z2, due to appropriate movement constraints provided by the bearing arrangement 600. For example, the bearing arrangement 600 may include a plurality of flexures for guiding tilting of the movable part 300 about the axes perpendicular to the primary axis Zl, Z2. Examples of such bearing arrangement 600 are described in WO2022 / 029441 Al, which is herein incorporated by reference.

[0115] Although the actuator assembly 1 is described herein in the context of four actuating units 400, in general the actuator assembly 1 may include fewer actuating units 400. For example, the actuator assembly 1 may include two actuating units 400, e.g. the two actuating units 400 depicted in the top left of Figure 8. The forces applied to the movable part 300 by the two actuating units 400 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 400 in the bottom right corner may be replaced with springs applying biasing forces along the corresponding depicted arrows, for example.

[0116] Optionally, the movable part 300 comprises an electronic component. The electronic component may be an image sensor. The electronic component may also be an emitter, a display, or a part thereof. Optionally, the movable part 300 comprises one or more lenses and / or an image sensor.

[0117] Optionally, the movable part 300 comprises an image sensor and a lens assembly configured to focus an image on the image sensor.

[0118] Other variations

[0119] It will be appreciated that there may be many other variations of the above-described examples.

[0120] SMA

[0121] 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 comprising: a support structure, with a first primary axis defined with reference to the support structure; an intermediate part that is movable relative to the support structure, with a second primary axis defined with reference to the intermediate part; a movable part that is movable relative to the intermediate part and the support structure; one or more tilt actuating units each configured to apply an actuating force capable of tilting the movable part relative to the support structure about a first tilt axis perpendicular to the first primary axis and / or a second tilt axis perpendicular to the second primary axis, wherein the first and second tilt axes are non-parallel axes; and one or more endstops configured, upon engagement, to limit axial translation of the movable part relative to the support structure along the first primary axis; and wherein the intermediate part is configured to elastically deform to allow the one or more endstops to engage.

2. An actuator assembly according to claim 1, wherein the one or more endstops are configured to prevent the intermediate part from undergoing plastic deformation.

3. An actuator assembly according to claim 1 or 2, wherein the actuating units are not configured to be capable of causing the one or more endstops to engage when the movable part is only subject to forces exerted by the actuating units, in addition to a gravitational force equivalent of lg.

4. An actuator assembly according to any preceding claim, wherein, when the movable part is only subject to forces exerted by the actuating units and a force of lg, the intermediate part is configured to not be able to elastically deform along the first primary axis by more than 5%, 10%, 20%, 30%, 40% or 50% of the amount of elastic deformation that the intermediate part has to undergo along the first primary axis to allow the one or more endstops to engage.

5. An actuator assembly according to any preceding claim, wherein each endstop comprises an endstop surface of the movable part and an endstop surface of the support structure, wherein theendstop surfaces are configured to engage each other upon engagement of the one or more endstops.

6. An actuator assembly according to any preceding claim, wherein the intermediate part is mounted on the support structure, and the movable part is mounted on the intermediate part.

7. An actuator assembly according to any preceding claim, comprising one or more tethering features configured to hold the intermediate part and the support structure together.

8. An actuator assembly according to any preceding claim, comprising one or more tethering features configured to hold the intermediate part and the movable part together.

9. An actuator assembly according to any preceding claim, wherein at least one of the tilt actuating units is configured to apply an actuating force capable of rotating the movable part relative to the support structure about the first and / or second primary axes.

10. An actuator assembly according to any preceding claim, comprising one or more rotation actuating units configured to apply an actuating force capable of rotating the movable part relative to the support structure about the first and / or second primary axes.

11. An actuator assembly according to any preceding claim, wherein at least one of the actuating units comprises an SMA (shape memory alloy) element configured, on actuation, to give rise to the actuating force.

12. An actuator assembly according to any preceding claim, wherein at least one of the actuating units comprises: a body portion; a shape memory alloy (SMA) element connected between the body portion and one of the support structure, the intermediate part, and the movable part, and configured, on actuation, to apply an input force to the body portion; and a force-modifying element connected between the body portion and the one of the support structure, the intermediate part, and the movable part, and configured to modify the input force so as to give rise to the actuating force.

13. An actuator assembly according to any preceding claim, comprising a first bearing arrangement configured to allow tilting of the intermediate part relative to the support structure about the first tilt axis, and to constrain tilting of the intermediate part relative to the support structure about the second tilt axis or an axis parallel to the second tilt axis.

14. An actuator assembly according to claim 13, wherein the first bearing arrangement is configured to allow rotation of the intermediate part relative to the support structure about the first primary axis.

15. An actuator assembly according to any preceding claim, comprising a second bearing arrangement configured to allow tilting of the movable part relative to the intermediate part about the second tilt axis, and to constrain tilting of the movable part relative to the intermediate part about the first tilt axis or an axis parallel to the first tilt axis.

16. An actuator assembly according to claim 15, wherein the second bearing arrangement is configured to allow rotation of the movable part relative to the intermediate part about the second primary axis.

17. An actuator assembly according to any preceding claim, wherein each of the one or more tilt actuating units is configured to exert a force on the movable part and / or the intermediate part with a component in a first direction along the first primary axis.

18. An actuator assembly according to any preceding claim, wherein the one or more tilt actuating units comprises: a first and a second actuating unit configured to tilt the movable part and the intermediate part relative to the support structure about the first tilt axis; and a third and a fourth actuating unit configured to tilt the movable part relative to the intermediate part and the support structure about the second tilt axis.

19. An actuator assembly according to claim 18, wherein the first and second actuating units are each configured to exert a force on the movable part and / or the intermediate part with a component in a first direction along the first primary axis, and the third and fourth actuating units are each configured to exert a force on the movable part with a component in a second opposite direction along the first primary axis.

20. An actuator assembly according to any preceding claim, wherein each tilt actuating unit is configured to apply the actuating force to the movable part.

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

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

23. An actuator assembly according to any preceding claim, wherein the movable part comprises an image sensor and a lens assembly configured to focus an image on the image sensor.

Images