Actuator assembly

Abstract

An actuator assembly (14) comprises a first portion (4) and a second portion (15) constrained to move along a first path (16) relative to the first portion (4) in a first plane (17). The actuator assembly (14) also includes a first set of one or more shape memory alloy wires (211, 212) configured to move the second portion (15) along the first path (16). The first set of shape memory alloy wires (211, 212) is arranged such that a movement of the second portion (15) is amplified relative to a corresponding change in length of the first set of shape memory alloy wires (211, 212). The actuator assembly (14) further comprises a third portion (18) constrained to move along a second path (19) relative to the second portion (15) in a second plane (20). The second plane (20) is parallel or coplanar with the first plane (17). The second path (19) is non-parallel to the first path (16). The actuator assembly (14) also includes a second set of one or more shape memory alloy wires (251, 252) configured to move the third portion (18) along a second path (19). The second set of shape memory alloy wires (251, 252) is arranged such that the movement of the third portion (18) is amplified relative to a corresponding change in length of the second set of shape memory alloy wires (251, 252).

Description

field

[0001] The present application relates to an actuator assembly, and in particular to an actuator assembly comprising a plurality of sections of shape memory alloy (SMA) wires. background

[0002] Such an actuator assembly may, for example, be used in a camera to move a lens assembly in a direction perpendicular to the optical axis in order to provide optical image stabilization (OIS). Where such a camera is to be incorporated into a portable electronic device such as a mobile phone, miniaturization may be important.

[0003] WO 2019 / 086855 A1 describes a camera with an actuator assembly, which includes a supporting platform, a moving platform supporting a lens assembly, an SMA wire connected to the supporting platform and the moving platform, a support member supporting the moving platform on the supporting platform, and two arms extending between the supporting platform and the moving platform. Overview

[0004] According to a first aspect of the present invention, an actuator assembly is provided, the actuator assembly comprising a first part and a second part, the second part being constrained to move along a first path relative to the first part in a first plane. The actuator assembly also includes a first group of one or more shape memory alloy wires, which are configured to move the second part along the first path. The first group of shape memory alloy wires is arranged so that the movement of the second part is amplified relative to the corresponding length change of the first group of shape memory alloy wires. The actuator assembly also includes a third part, which is constrained to move along a second path relative to the second part in a second plane. The second plane is parallel or coplanar with the first plane. The second path is not parallel to the first path. The actuator assembly also includes a second group of one or more shape memory alloy wires, which are configured to move the third part along the second path. The second group of shape memory alloy wires is arranged so that the movement of the third part is amplified relative to the corresponding length change of the second group of shape memory alloy wires.

[0005] Thus, movement of the third part relative to the first part in the second plane is a combination of movement of the second part relative to the first part and movement of the third part relative to the second part.

[0006] The first path may be a straight line or at least substantially a straight line. The second path may be a straight line or at least substantially a straight line. The first path and the second path may be orthogonal axes. However, typically, the first path may be curved and / or the second path may be curved.

[0007] Each shape memory alloy wire in the first group can be fixed between the second part and the first part. Each shape memory alloy wire in the first group can be fixed to the second part at one end and to the first part at the other end. Alternatively, each shape memory alloy wire in the first group can be fixed to the second part at one or more points along its length and fixed to the first part at both ends. Similarly, each shape memory alloy wire in the first group can be fixed to the first part at one or more points along its length and fixed to the second part at both ends.

[0008] Each shape memory alloy wire in the second group can be fixed between the third part and the second part. Each shape memory alloy wire in the second group can be fixed to the third part at one end and to the second part at the other end. Alternatively, each shape memory alloy wire in the second group can be fixed to the third part at one or more points along its length and fixed to the second part at both ends. Each shape memory alloy wire in the second group can be fixed to the second part at one or more points along its length and fixed to the third part at both ends.

[0009] The second part may have one degree of freedom relative to the first part, i.e. move in one degree of freedom. The third part may have one degree of freedom relative to the second part, i.e. move in one degree of freedom in addition to the degree of freedom with which the second part moves relative to the first part. Thus, the third part may have two independent degrees of freedom relative to the first part, i.e. move in two degrees of freedom.

[0010] Each shape memory alloy wire in the first group may have a span length between the attachment points (or fixing / contact points) that is at least 80% of the side length of the second portion. Additionally or alternatively, each shape memory alloy wire in the second group may have a span length between the attachment points (or fixing / contact points) that is at least 80% of the side length of the third portion.

[0011] Each shape memory alloy wire in the first group may include a single span. Additionally or alternatively, each shape memory alloy wire in the second group may include a single span. Thus, the shape memory alloy wires may extend in a single straight line between the portions to which they are connected.

[0012] Thus, when viewed perpendicular to the first plane, none of the shape memory alloy wires in the first group are configured in a V-shape. When viewed perpendicular to the second plane, none of the shape memory alloy wires in the second group are configured in a V-shape. In other words, none of the shape memory alloy wires in the first group or the second group are fixed at the first end and the second end and hooked (not fixed) on a retention feature that is not co-linear with the first end and the second end.

[0013] The first set of shape memory alloy wires may be configured to apply a net moment between the first portion and the second portion. Although the first set of shape memory alloy wires may apply a net moment between the first portion and the second portion, rotation of the second portion relative to the first portion may be constrained, for example, by one or more bearings, flexures, etc. The constraint on rotation may be provided by the same features that constrain the first portion to move along the first path.

[0014] The second set of shape memory alloy wires can be configured to apply a net moment between the second portion and the third portion. Although the second set of shape memory alloy wires can apply a net moment between the second portion and the third portion, the rotation of the third portion relative to the second portion can be constrained, for example, by one or more supports, flexures, etc. The constraint on rotation can be provided by the same features that constrain the third portion to move along the second path.

[0015] The first group of shape memory alloy wires may consist of two shape memory alloy wires, and each shape memory alloy wire in the first group may include a single straight span. Additionally or alternatively, the second group of shape memory alloy wires may consist of two shape memory alloy wires, and each shape memory alloy wire in the second group may include a single straight span.

[0016] The first path may be substantially parallel (including parallel) to the first axis. The second path may be substantially parallel (including parallel) to the second axis. The first axis and the second axis may form an angle between 10° and 90° with each other. In some embodiments, the first axis and the second axis are substantially perpendicular to each other.

[0017] The actuator assembly may include a first support device connecting the first part and the second part. The first support device may be configured to constrain the movement of the second part relative to the first part to a first plane and / or to a first path. The actuator assembly may include a second support device connecting the third part and the second part. Alternatively, the actuator assembly may include a second support device connecting the third part and the first part. In either case, the second support device may be configured to constrain the movement of the third part relative to the second part to a second plane and / or to a second path.

[0018] By constraining the second / third part so that it cannot move directly in the contraction direction of the shape memory alloy wire in the first group / second group, the movement of the second / third part can be amplified relative to the corresponding length change of the shape memory alloy wire. In other words, the shape memory alloy wire in the first group is not parallel to the first path, and the shape memory alloy wire in the second group is not parallel to the second path. The constraint that causes amplification can be provided by one or more elastic elements, which can be included by the first and / or second support device. The elastic element can include a spring or take the form of a spring. The elastic element can include a flexure or take the form of a flexure. The constraint that causes amplification can be provided by one or more other types of bearings (included by the first and / or second support device), such as roller bearings, plain bearings, sliding bearings, etc. The constraint that causes amplification can be provided by a combination of two or more of the following: other shape memory alloy wires in the corresponding first group / second group, one or more elastic elements, one or more springs, one or more flexures, and one or more bearings.

[0019] The movement of the second portion can be amplified relative to the corresponding length change of the shape memory alloy wire in the first group because the shape memory alloy wire forms an angle less than 90° and greater than 0° relative to the first path. The movement of the third portion can be amplified relative to the corresponding length change of the shape memory alloy wire in the second group because the shape memory alloy wire forms an angle less than 90° and greater than 0° relative to the second path.

[0020] Each shape memory alloy wire in the first group can form an angle between 20° and 80° with the first path, including the endpoints. Preferably, each shape memory alloy wire in the first group can form an angle between 45° and 77° with the first path, including the endpoints. The lower limit of the angle ensures that sufficient stroke amplification is achieved. The upper limit of the angle ensures that the movement of the second part can be accurately and reliably controlled.

[0021] Similarly, each shape memory alloy wire in the second group may form an angle between 20° and 80°, inclusive, with the second path. Each shape memory alloy wire in the second group may form an angle between 45° and 77°, inclusive, with the second path.

[0022] When the first path is not straight, if all points along the first path (and within the range of motion of the second portion relative to the first portion) are aligned with the shape memory alloy wires in the first group in the range θ min to θ max The angle between the shape memory alloy wire and the first path is θ. minto θ max When the second path is not straight, if all points along the second path (and within the range of motion of the third part relative to the second part) are in the range θ with the shape memory alloy wires in the second group, min to θ max The angle between the shape memory alloy wire and the second path is θ. min to θ max in the range between.

[0023] The constraint of the second part on the first path may include one or more first flexures or take the form of one or more first flexures. Additionally or alternatively, the constraint of the third part on the second path may include one or more second flexures or take the form of one or more second flexures. The first flexure and / or the second flexure may be included by the first support device and / or the second support device, respectively.

[0024] Each first flexure may be axially loaded in response to actuation of the first set of shape memory alloy wires. Additionally or alternatively, each second flexure may be axially loaded in response to actuation of the second set of shape memory alloy wires. The axial loading of the first and / or second flexures may correspond to at least 5%, preferably at least 20% or at least 50% of the tension in the SMA wires of the flexures.

[0025] Thus, each first flexure can be axially loaded under tension in response to actuation of a corresponding shape memory alloy wire in the first group. Each first flexure can be axially loaded under compression in response to actuation of a corresponding shape memory alloy wire in the first group. Each second flexure can be axially loaded under tension in response to actuation of a shape memory alloy wire in the second group. Each second flexure can be axially loaded under compression in response to actuation of a shape memory alloy wire in the second group. Preferably, the first flexure and / or the second flexure are placed in a state of tension, thereby reducing the risk of buckling of the flexure compared to a situation where the flexure is placed in a state of compression.

[0026] Each first flexure can connect the corresponding edge of the second part to the first part. Each first flexure can form an angle between 0 ° and 45 ° with the corresponding edge of the second part. Each shape memory alloy wire in the first group can connect the corresponding edge of the second part to the first part. Each shape memory alloy wire in the first group can form an angle between 0 ° and 45 ° with the corresponding edge of the second part. The first flexure connected to the same edge of the second part and the shape memory alloy wire in the first group can form an angle between 13 ° and 45 ° with each other. The first flexure can form an angle of substantially 90 ° relative to the first path.

[0027] Each second flexure can connect the corresponding edge of the third part to the second part. Each second flexure can form an angle between 0 ° and 45 ° with the corresponding edge of the third part, preferably an angle between 0 ° and 20 °, and further preferably an angle between 0 ° and 10 °. The lower angle reduces the range of the actuator assembly in the direction orthogonal to the edge of the actuator assembly, thereby reducing the footprint of the actuator assembly. Each shape memory alloy wire in the second group can connect the corresponding edge of the third part to the second part. Each shape memory alloy wire in the second group can form an angle between 0 ° and 45 ° with the corresponding edge of the third part, preferably an angle between 0 ° and 20 °, and further preferably an angle between 0 ° and 10 °. The second flexure connected to the same edge of the third part and the shape memory alloy wire in the second group can form an angle between 13 ° and 45 ° with each other. The second flexure can form an angle of substantially 90 ° relative to the second path.

[0028] Reference to the angle formed by the shape memory alloy wires in the first and / or second groups may refer to an equilibrium state of the actuator assembly, for example, when none of the shape memory alloy wires are actuated or when the portion is in a central position.

[0029] The actuator assembly may also include a controller configured to control the selective contraction of the shape memory alloy wires in the first group so as to move the second portion along the first path relative to the first portion. The control of the second portion may be achieved by controlling a drive signal (e.g., a drive current or a drive voltage) supplied to the first group of shape memory alloy wires. The controller may also be configured to control the selective contraction of the shape memory alloy wires in the second group so as to move the third portion along the second path relative to the second portion. The control of the third portion may be achieved by controlling a drive signal (e.g., a drive current or a drive voltage) supplied to the second group of shape memory alloy wires.

[0030] The second part of the constraint on the first path may include one or more first rolling bearings or take the form of one or more first rolling bearings. Additionally or alternatively, the third part of the constraint on the second path may include one or more second rolling bearings or take the form of one or more second rolling bearings. The first and / or second rolling bearings may be comprised by the first and / or second bearing means.

[0031] The first rolling bearing may include a first ball bearing race or take the form of a first ball bearing race, which is formed between the second part and the first part and holds one or more ball bearings. The first ball bearing race may at least partially define the first path. The first ball bearing race may be aligned with the first path. The second rolling bearing may include a second ball bearing race or take the form of a second ball bearing race, which is formed between the third part and the second part and holds one or more ball bearings. The second ball bearing race may at least partially define the second path. The second ball bearing race may be aligned with the second path. Alternatively, the rolling bearing may include a roller (e.g., a cylindrical rolling element) between the two bearing surfaces.

[0032] The contraction of each shape memory alloy wire in the first group can be opposed by one or more other shape memory alloy wires in the first group. Additionally or alternatively, the contraction of each shape memory alloy wire in the second group can be opposed by one or more other shape memory alloy wires in the second group. Providing opposing shape memory alloy wires allows control of tension in the shape memory alloy wires, thereby allowing more accurate and reliable movement control.

[0033] Thus, the first set of shape memory alloy wires may include a first shape memory alloy wire and a second shape memory alloy wire, and may be configured such that, relative to the first portion: actuation of the first shape memory alloy wire urges the second portion in a first direction along a first path; Actuation of the second shape memory alloy wire urges the second portion along the first path opposite to the first direction.

[0034] The second set of shape memory alloy wires may include a third shape memory alloy wire and a fourth shape memory alloy wire, and may be configured such that, relative to the second portion: actuation of the third shape memory alloy wire urges the third portion in a second direction along a second path; Actuation of the fourth shape memory alloy wire urges the third portion along the second path opposite to the second direction.

[0035] Alternatively, contraction of each shape memory alloy wire in the first group may be opposed by one or more springs coupling the first portion to the second portion. Contraction of each shape memory alloy wire in the second group may be opposed by one or more springs coupling the first portion to the second portion. The springs (opposed by the SMA wires in the first or second group) may take the form of coil springs, flat springs, leaf springs, flexures, elements formed from elastomeric materials, etc.

[0036] The first plane and the second plane may be coplanar. The second portion may surround the third portion. The third portion may surround the second portion. Alternatively, the first plane and the second plane may be parallel. Any or all of the first portion, the second portion, and the third portion may be stacked sequentially along a vertical direction perpendicular to the first and second planes.

[0037] The third portion may include a central hole, and no shape memory alloy wire may pass through the central hole. Therefore, no shape memory alloy wire belonging to the first group may pass through the central hole. No shape memory alloy wire belonging to the second group may pass through the central hole.

[0038] The third part may have a first surface and a second surface, and the second surface is opposite to the first part across the gap. The shape memory alloy wire belonging to the first group may be wired through the gap. In other words, the shape memory alloy wire belonging to the first group may be wired through the space formed between the first part and the third part. Additionally or alternatively, the shape memory alloy wire belonging to the second group may be wired through the gap. In other words, the shape memory alloy wire belonging to the second group may be wired through the space formed between the first part and the third part. The shape memory alloy wire in the first group and / or the second group may be arranged diagonally in the gap, thus extending between the corner portions of the first part, the second part and / or the third part. Compared with the situation where the shape memory alloy wire is not arranged diagonally, this allows the shape memory alloy wire to be made longer.

[0039] The third portion may have a first surface and a second surface, the second surface opposite the first portion across the gap. At least one first flexure may be routed through the gap. Additionally or alternatively, at least one second flexure may be routed through the gap.

[0040] The actuator assembly may include additional parts, such as a fourth part, a fifth part, etc. Under the control of the additional set of shape memory alloy wires, the additional parts may be constrained to move along additional paths. The additional parts may be configured and / or constrained in any manner described herein with respect to the first part, the second part, and / or the third part.

[0041] According to a second aspect of the present invention, there is provided a method for controlling a shape memory alloy actuator according to the first aspect. The method comprises controlling a second portion to move relative to the first portion along a first path in a first plane. The method further comprises controlling a third portion to move relative to the second portion along a second path in a second plane.

[0042] The method according to the second aspect may include features corresponding to any features of the shape memory alloy actuator of the first aspect.The definitions applicable to the shape memory alloy actuator of the first aspect may equally apply to the method according to the second aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] 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 A camera is shown; Figure 2 is a plan view of a first actuator assembly; Figure 3A and Figure 3B A stroke amplification mechanism using a shape memory alloy wire is shown; 4A to 4D is a plan view of the second actuator assembly. Figure 4D shows a plan view of a second actuator assembly, and FIG. 4A to FIG. 4C shows a plan view of a second actuator assembly with selected portions omitted for visual clarity; Figure 5A is a plan view of a third actuator assembly; Figure 5B Shown along Figure 5A A cross section of the line marked AA* in FIG. Figure 5C Shown along Figure 5A Cross section of the line marked BB* in . Detailed Description

[0044] Reference Figure 1 , a camera 1 is shown including an SMA actuator assembly 2 (also referred to herein as an “SMA actuator” or an “actuator assembly”).

[0045] The camera 1 comprises a lens assembly 3 suspended on a first part 4 (or "support structure") by an actuator assembly 2 which supports the lens assembly 3 in a manner allowing movement of the lens assembly 3 relative to the first part 4 in a direction perpendicular to the optical axis O (in a first plane).

[0046] The first part 4 comprises a base 5. An image sensor 6 is mounted on the front side of the base 5. A controller 7 is mounted on the rear side of the base 5. For example, the controller 7 may take the form of an integrated circuit (IC) in which a control circuit is implemented. Optionally, for example when the camera 1 is configured with an optical image stabilization (OIS) function, a gyroscopic sensor 8 may be mounted on the rear side of the base 5 and coupled to the controller 7. The precise location at which the controller 7 (and optionally the gyroscopic sensor 8, if present) is mounted relative to the actuator assembly 2 is not critical, but it is preferred that the arrangement is compact.

[0047] The first portion 4 further includes a shielding cover (or “cover”) 9 that protrudes forward from the base 5 to enclose and protect other components of the camera 1 .

[0048] The lens assembly 3 comprises a lens holder 10 in the form of a cylindrical body, which supports two lenses 11 arranged along an optical axis O (parallel to the z-axis shown). Generally, any number of one or more lenses 11 may be included. Preferably, each lens 11 has a diameter of at most about 20 mm. Therefore, the camera 1 may be referred to as a miniature camera.

[0049] The lens assembly 3 is arranged to focus the image onto an image sensor 6. The image sensor 6 captures the image and may be of any suitable type, such as a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS) device.

[0050] The lens 11 is supported on the lens holder 10 so that the lens 11 can move relative to the lens holder 10 along the optical axis O, for example, to provide focusing or zooming. Specifically, the lens 11 is fixed to a lens holder 12 that is movable relative to the lens holder 10 along the optical axis O. In this example, although all of the lenses 11 are fixed to the lens holder 12, in general, one or more of the lenses 11 may be fixed to the lens holder 10 and may not move relative to the lens holder 10 along the optical axis O, so that at least one of the lenses 11 is fixed to the lens holder 12.

[0051] An axial actuator assembly 13 disposed between the lens holder 10 and the lens holder 12 is arranged to drive movement of the lens holder 10 and the lens 11 relative to the lens holder 10 along the optical axis O. The axial actuator device 13 may be of any suitable type, for example a voice coil motor (VCM) or an SMA wire device.

[0052] In operation, the lens assembly 3 is moved relative to the image sensor 6 orthogonal to the optical axis O by the actuator assembly 2, having the effect of moving the image on the image sensor 6. This serves to provide optical image stabilisation (OIS), compensating for movement of the camera 1 which may be caused by hand shake or the like.

[0053] First actuator assembly Also refer to Figure 2 , a first exemplary actuator assembly 14 (hereinafter referred to as “first actuator assembly”) is shown.

[0054] The first actuator assembly 14 may provide the actuator assembly 2 of the camera 1, but is not limited to use in the camera 1. The first actuator assembly 14 includes a first portion 4 (also referred to as a "support structure"), a second portion 15 (also referred to as a "middle portion"), and a third portion 18 (also referred to as a "moving portion"), the second portion 15 being constrained to move along a first path 16 relative to the first portion in a first plane 17, and the third portion 18 being constrained to move along a second path 19 relative to the second portion 15 in a second plane 20. In the first actuator assembly 14, the second plane 20 is coplanar with the first plane 17. However, in variations of the first actuator assembly 14, the first plane 17 and the second plane 20 need not be coplanar, and may be parallel to each other at different heights along a vertical direction (as shown in the z-axis).

[0055] The first actuator assembly 14 includes a first group of shape memory alloy (SMA) wires 21 configured to move the second portion 15 relative to the first portion 4 along the first path 16. The first actuator assembly 14 has a first side 221, a second side 222, a third side 223, and a fourth side 224, and the first group of shape memory alloy wires 21 includes a first SMA wire 211 and a second SMA wire 212 arranged along the first side 221 and the third side 223 of the first actuator assembly 14, respectively. Generally, the first group may include more or fewer SMA wires 21, but the minimum number is one (whose contraction should be opposed by a spring as described below). In the first actuator assembly 14, each SMA wire 21 in the first group is fixed to the first portion 4 at one end by a first crimping piece 23, and fixed to the second portion 15 at the other end by a second crimping piece 34. The SMA wires 21 in the first set need not be attached between the first portion 4 and the second portion 15 by crimping, and may be secured between the first portion 4 and the second portion 15 in any suitable manner.

[0056] The first actuator assembly 14 also includes a second set of shape memory alloy wires 25 configured to move the third portion 18 relative to the second portion 15 along the second path 19. In the first actuator assembly 14, the second set of shape memory alloy wires 25 includes a first SMA wire 251 and a second SMA wire 252 arranged along the fourth side 224 and the second side 222 of the first actuator assembly 14, respectively. Generally, the second set may include more or fewer SMA wires 25, but the minimum number is one (whose contraction should be opposed by a spring as described below). Each SMA wire 25 in the second set is fixed to the second portion 15 at one end by a corresponding third crimping piece 26, and fixed to the third portion 18 at the other end by a corresponding fourth crimping piece 27. The SMA wires 25 in the first set do not need to be attached between the second portion 15 and the third portion 18 by crimping, and can be fixed between the second portion 15 and the third portion 18 in any suitable manner.

[0057] In this way, the second portion 15 is coupled to the first portion 4 via the first set of shape memory alloy wires 21, and the third portion 18 is coupled to the second portion 15 via the second set of shape memory alloy wires 25. Therefore, the movement of the third portion 18 relative to the first portion 4 is a combination of the movement of the second portion 15 relative to the first portion 4 along the first path 16 and the movement of the third portion 18 relative to the second portion 15 along the second path 19.

[0058] In the first actuator assembly 14, constraint of the second part 15 to move along the first path 16 relative to the first part 4 is provided by a pair of first flexures 281, 282 connecting the second part 15 to the first part 4 along the first edge 221 and the third edge 223. Each first flexure 281, 282 is connected to the first part 4 at a first end 291, 292 and to the second part 15 at a second opposite end 301, 302. The first flexures 281, 282 are parallel to each other but oppositely oriented between the respective first ends 291, 292 and the second part 15. The first flexures 281, 282 have a relatively high compliance to lateral deflection in the first plane 17 and a relatively low, preferably negligible, compliance along the length of each flexure 281, 282. The parallel first flexures 281, 282 arranged on the opposite edges 221, 223 of the second part 15 constrain the movement of the second part 15 relative to the first part 4 to follow the first path 16. For visualization, the first line 161 and the second line 162 are Figure 2 1 is drawn to indicate the movement of the second ends 301 , 302 of the first flexures 281 , 282 when the second portion 15 is deflected along the first path 16 .

[0059] Similarly, in the first actuator assembly, constraint of the third portion 18 to move relative to the second portion 15 along the second path 19 is provided by a pair of second flexures 311, 312 connecting the third portion 18 to the second portion 15 along the fourth side 224 and the second side 222. Each second flexure 311, 312 is connected to the second portion 15 at a first end 321, 322 and to the third portion 18 at a second opposite end 331, 332. The second flexures 311, 312 are parallel to each other but oppositely oriented between the respective first ends 321, 322 and the third portion 18. Similar to the first flexures 281, 282, the second flexures 311, 312 have a relatively high compliance to lateral deflection in the second plane 20 and a relatively low, preferably negligible, compliance along the length of each flexure 311, 312. Parallel second flexures 311, 312 arranged on opposite sides 222, 224 of the third portion 18 constrain the movement of the third portion 18 relative to the second portion 15 to follow the second path 19. For visualization, the first line 191 and the second line 192 are Figure 2 3 is drawn to indicate the movement of the second ends 331 , 332 of the second flexures 311 , 312 when the third portion 18 is deflected along the second path 19 .

[0060] Another way to describe the constraints is that the second portion 15 has one degree of freedom (along the first path 16) relative to the first portion 4, and the third portion 18 has one degree of freedom (along the second path) relative to the second portion 15. However, because the first and second degrees of freedom (paths 16, 19) are not parallel, the third portion 18 has two independent degrees of freedom relative to the first portion 4 overall.

[0061] The first and second paths 16, 19 will be substantially linear for small deflections of the respective portions 15, 18 and will be substantially linear for small deflections of the respective portions 15, 18. Figure 2 1 and 2 have been drawn as linear because the SMA actuator assemblies 2, 14 are generally intended for relatively small precision movements. It will be appreciated that as the respective portions 15, 18 are deflected by the SMA wires 21, 25, the first and second paths 16, 19 will begin to bend further from the equilibrium state.

[0062] The SMA wires 21 in the first group and the SMA wires 25 in the second group can be contracted by resistive heating provided by the current. The electrical connection between the first part 4 and the second part 15 can be supported on (or provided by) the first flexures 281, 282 connecting the first part 4 and the second part 15. Each first flexure 281, 282 can support, for example, one, two or more separate electrical connections that are insulated from each other. Alternatively, an additional flexure (not shown) can be connected between the first part 4 and the second part 15 to support the electrical connection. Such an additional flexure (not shown) should have a high degree of compliance to avoid or at least minimize interference with the movement of the second part 15 relative to the first part 4 along the first path 16. Similarly, the electrical connection between the first part 4 and the third part 18 can be routed via a combination of the second flexures 311, 312 and the first flexures 281, 282. For example, each second flexure 311, 312 can support, for example, one, two or more separate electrical connections that are insulated from each other. Alternatively, an additional flexure (not shown) may be connected between the third portion 18 and the second portion 15, or directly to the first portion 4, to support the electrical connection. Such an additional flexure (not shown) should be highly compliant to avoid or at least minimize interference with the movement of the third portion 18 relative to the second portion 15 along the second path 19. Alternative options for achieving the electrical connection may include sliding spring contacts, conductive ball bearings, etc.

[0063] When one of the SMA wires 21, 25 is heated, the stress in the SMA wire 21, 25 increases and it contracts, thereby providing a force that forces the portions 4, 15, 18 between which the SMA wires 21, 25 are connected to pull toward each other (and move if there is a net force along an unconstrained direction such as the first path 16 or the second path 19). A series of movements occur as the temperature of the SMA material increases within the temperature range where the SMA material transformation from the martensite phase to the austenite phase occurs. Conversely, when one of the SMA wires 21, 25 is cooled so that the stress in the SMA wire 21, 25 is reduced, it can extend under the action of the force from the opposing wire of the SMA wires 21, 25 and / or the restoring force caused by the deflection of the flexures 281, 282, 311, 312. The SMA wires 21, 25 can be made of any suitable SMA material, such as Nitinol or another titanium alloy SMA material.

[0064] The drive signal for the SMA wires 21, 25 is generated and provided by the controller 7, such as a control circuit implemented in an IC as described above. For example, the drive signal can be generated by the controller 7 in response to the output signal of the gyro sensor 8 to drive the movement of the lens assembly 3 to stabilize the image focused on the image sensor 6 by the lens assembly 3, thereby providing OIS. The drive signal can be generated using a resistive feedback control technique, for example, as described in WO 2014 / 076463 A1, which disclosure is incorporated herein by reference. An example of the operation of the controller 7 controlling the first actuator assembly 14 is described below.

[0065] In operation, the SMA wires 21, 25 are selectively driven to move the third portion 18 in any lateral direction (i.e., a direction perpendicular to the vertical direction z) relative to the first portion 4 by a combination of a first displacement of the second portion 15 along the first path 16 and a second displacement of the third portion 18 along the second path 19. Background details of the method of driving the SMA wires 21, 25 are also provided in WO2013 / 175197A1, which is incorporated herein by reference.

[0066] The first actuator 14 is a square having a first side 221, a second side 222, a third side 223, and a fourth side 224. The first side 221 and the third side 223 are parallel to each other and to the x-axis as shown in the figure. The second side 222 and the fourth side 224 are parallel to each other and to the y-axis as shown in the figure, which is perpendicular to the x-axis. In the first actuator 14, the side 22 of the actuator 14 coincides with the edge of the first part 4, which takes the form of a square plate. The first part 4 can provide a base 5 if used in the camera 1. Each of the second part 15 and the third part 18 takes the form of a flat thin ring having a square outer edge and an inner edge, defining a hole 34. When used in the camera 1, the hole 34 allows light focused by the lens 11 to pass to the image sensor 6 (e.g., mounted on the first part 4). Therefore, neither of the SMA wires 21, 25 intersects the hole 34 of the third part 18. The third portion 18 is smaller than the second portion 15 and is received in the aperture 34 of the second portion 15 such that the second portion 15 and the third portion 18 are substantially coplanar and the first plane 17 and the second plane 20 coincide. The first portion 4, the second portion 15 and the third portion 18 are each substantially perpendicular to a vertical axis (the z-axis as shown). When used in a camera, the vertical axis z will be parallel to the optical axis O.

[0067] The first part 4, the second part 15 and the third part 18 may take the form of respective patterned metal sheets, such as etched or machined stainless steel, and may be coated with an electrically insulating dielectric material. The dielectric material layer may include one or more windows (not shown) to allow electrical connection.

[0068] Other example configurations may be used, and further examples are provided in WO 2017 / 055788 A1 and WO 2019 / 086855 A1, which are incorporated herein by this reference.

[0069] The second portion 15 is constrained to move along the first path 16 by the first flexures 281, 28. In some examples, the first flexures 281, 282 can additionally constrain the second portion 15 to move within the first plane 17, for example, the first flexures 281, 282 can be configured to have a relatively low compliance for deflection perpendicular to the first plane 17 (i.e., in the vertical direction z). Additionally or alternatively, the second portion 15 can be constrained within the first plane 17 at least in part using a first support device (not shown) that couples the second portion 15 to the first portion 4. The first portion 15 can be maintained in contact with the first support device (not shown) by the first flexures 281, 282, one or more additional flexures (not shown), a spring (not shown), or a similar device that provides a force along the vertical axis z to urge the second portion 15 toward the first portion 4.

[0070] Similarly, the third portion 18 is constrained to move along the second path 19 by the second flexures 311, 312. In some examples, the second flexures 311, 312 can additionally constrain the third portion 18 to move within the second plane 20, for example, the second flexures 311, 312 can be configured to have a relatively low compliance for deflection perpendicular to the second plane 20 (i.e., in the vertical direction z). Additionally or alternatively, the third portion 18 can be constrained within the second plane 20 at least in part using a second support device (not shown) that couples the third portion 18 to the second portion 15. The second portion 15 and the third portion 18 can be maintained in contact with the second support device (not shown) by the second flexures 311, 312, one or more additional flexures (not shown), a spring (not shown), or a similar device that provides a force along the vertical axis z to push the second portion 15 and the third portion 18 toward each other. Alternatively, the second support device (not shown) can couple the third portion 18 directly to the first portion 4.

[0071] The first support means and / or the second support means (not shown) may take the form of three or more planar supports, three or more roller supports, a further set of flexures (not shown), or the like.

[0072] SMA wire placement for the first actuator assembly The first group of SMA wires 21 are arranged in a loop around the hole 34, wherein the first SMA wire 211 of the first group opposes the first 281 of the first flexures along the first side 221, and the second SMA wire 212 of the first group opposes the second 282 of the first flexures along the third side 223. The first group of SMA wires 211, 212 are parallel to each other. The arrangement of the second SMA wire 212 of the first group and the corresponding first flexure 28 is rotated 180° relative to the first SMA wire 211 of the first group and the corresponding first flexure 281. The two SMA wires 211, 212 of the first group form substantially the same angle with the x-axis and the y-axis. The angle formed by the first group of SMA wires 21 with the y-axis is smaller than the angle formed with the x-axis.

[0073] Actuation to retract the first SMA wire 211 in the first group pushes the second portion 15 toward the left hand side of the illustration (in the negative x-direction, but not parallel thereto) relative to the first portion 4 along the first path 16. The second SMA wire 212 in the first group is then actuated to retract in order to push the second portion 15 in the opposite direction (in the positive x-direction, but not parallel thereto) along the first path 16. When none of the SMA wires 21 in the first group are actuated, the first flexures 281, 282 push the second portion 15 back to an equilibrium position relative to the first portion 4.

[0074] By actuating any one of the SMA wires 211, 212 in the first group, a clockwise moment is applied to the second portion 15 relative to the first portion 4. However, the second portion 15 does not rotate due to the constraints of the first flexures 281, 282. Therefore, each first flexure 281, 282 is axially loaded (in tension) in response to the actuation of the first group of shape memory alloy wires 21.

[0075] The second group of SMA wires 25 are also arranged in a loop around the hole 34, wherein the first SMA wire 251 in the second group opposes (in terms of contraction) the first of the second flexures 311 along the fourth side 224, and the second SMA wire 252 in the second group opposes the second of the second flexures 312 along the second side 222. The arrangement of the second SMA wire 252 in the second group and the corresponding second flexure 312 is rotated 180° relative to the first SMA wire 251 in the second group and the corresponding second flexure 311. The two SMA wires 251, 252 in the second group form substantially the same angle with the x-axis and the y-axis. The angle formed by the second group of SMA wires 25 with the x-axis is smaller than the angle formed with the y-axis.

[0076] By actuating any one of the SMA wires 251, 252 in the second group, a clockwise moment relative to the second part 15 is applied to the third portion 18. However, the third portion 18 does not rotate due to the constraints of the second flexures 311, 312. Therefore, each second flexure 311, 312 is axially loaded (in tension) in response to the actuation of the second group of shape memory alloy wires 25.

[0077] The total movement of the third portion 18 relative to the first portion 4 is the sum of the movement of the second portion 15 relative to the first portion 4 along the first path 16 (from the actuation of the first set of SMA wires 21) and the movement of the third portion 18 relative to the second portion 15 along the second path 19 (from the actuation of the second set of SMA wires 25). Although slightly tilted relative to the edge 22 of the actuator assembly (and the x-axis and y-axis as shown), the first path 16 and the second path 19 allow two degrees of freedom of lateral movement of the third portion 18 relative to the first portion 4 (perpendicular to the vertical direction z). The first path 16 can correspond to the first axis and the second path 19 can correspond to the second axis.

[0078] The first set of shape memory alloy wires 21 are arranged such that movement of the second portion 15 relative to the first portion 4 along the first path 16 is amplified compared to a corresponding change in length of the first set of shape memory alloy wires 21. Similarly, the second set of shape memory alloy wires 25 are arranged such that movement of the third portion 18 relative to the second portion 15 along the second path 19 is amplified compared to a corresponding change in length of the second set of shape memory alloy wires 25.

[0079] SMA wire zoom Also refer to Figure 3A and Figure 3B , showing the SMA wire 21, 25 amplification mechanism.

[0080] Special reference Figure 3A , the angled SMA wire 35 forms an angle θ with the x-axis and an angle 90-θ with the y-axis. Figure 3A In the example shown, the angle is θ=45°.

[0081] The SMA wire 35 has an initial length L, a component x0 along the x-axis and a component y0 along the y-axis. The first end 36 of the SMA wire 35 is fixed to Figure 3A The origin of the axis xy drawn in .

[0082] The SMA wire 35 is then actuated (by resistive heating using a drive current) and caused to contract by an amount δL to a new length L-δL. The locus of points that the second end 37 of the SMA wire 35 can reach is referenced Figure 3AA circle 38 of radius L-δL is drawn in FIG. 3. If the second end 37 of the SMA wire 35 is unconstrained, or is constrained to move in the direction in which the SMA wire 35 lies (θ=45°), then the total displacement of the second end 37 relative to the first end will simply be δL to the point marked P1. This represents an unamplified displacement, and many SMA actuators operate in this manner, pulling a portion of the actuator directly along the length of the SMA wire 35. However, this limits the travel of such an actuator to a maximum length change of δL.

[0083] However, if the second end 37 is constrained to move along a path that is not parallel to the initial orientation of the SMA wire 35 (e.g., the first path 16 or the second path 19), then amplification can be obtained. For example, if the second end 37 is constrained to move parallel to the y-axis, then the second end 37 is forced to reach a point P2 on the circle 38 that intersects the original component x0 along the x-axis. Then the total displacement is Δy = y0-y1>δL. Alternatively, if the second end 37 is constrained to move parallel to the x-axis, then the second end 37 is forced to reach a point P3 on the circle 38 that intersects the sub-original component y0 along the y-axis. Then the total displacement is Δx = x0-x1>δL.

[0084] for Figure 3A For the geometry shown, where θ = 45°, the amplification is the same when constrained to the x-axis or the y-axis, i.e., Δx = Δy, and the gain is Δx / δL ≈ 1.5.

[0085] By changing the initial orientation angle θ, the gain for movement parallel to one axis x, y can be increased at the expense of reduced gain for movement parallel to the other axis y, x.

[0086] Also refer to Figure 3B , which shows that Figure 3A Same configuration, except the angle is θ=60° instead of θ=45°. Figure 3B In the configuration of θ=45°, when the second end 37 is constrained to move parallel to the x-axis to point P3, the gain increases to Δx / δL≈2.4. However, when the second end 37 is constrained to move parallel to the y-axis to point P2, the gain decreases (compared to θ=45°) to Δy / δL≈1.2.

[0087] Constraining the second end 37 to any other path not parallel to θ will result in amplification since the shortest displacement corresponding to a change in length δL (zero amplification) will always be directly along the initial orientation of the SMA wire 35. In other words, amplification need not be strictly constrained to the x-axis or y-axis.

[0088] Reference again Figure 2, the SMA wires 21 in the first set are angled relative to the first path 16 so that the movement of the second portion 15 along the first path 16 is amplified relative to the first portion 4 (constraints created by the first flexures 281, 282). Similarly, the SMA wires 25 in the second set are angled relative to the second path 19 so that the movement of the third portion 18 along the second path is amplified relative to the second portion 15 (constraints created by the second flexures 281, 282).

[0089] In general, to optimize the amplification (gain) relative to the net component of the force in the desired direction, each SMA wire 21 in the first group preferably forms an angle between 45° and 77° (including 45° and 77°) with the first path 16. In the first actuator assembly 14, the first path 16 is generally perpendicular to the first flexure 28. Similarly, each SMA wire 25 in the second group preferably forms an angle between 45° and 77° (including 45° and 77°) with the second path 19. In the first actuator assembly 14, the second path 19 is generally perpendicular to the second flexure 31.

[0090] Alternatively, each SMA wire 21 of the first set may form an angle between 10° and 80° (inclusive) with the first path 16 , and each SMA wire 25 of the second set may form an angle between 10° and 80° (inclusive) with the second path 19 .

[0091] The controller 7 is configured to control the selective contraction of the SMA wires 21 in the first group so as to move the second portion 15 by an amount Δ1 relative to the first portion 4 along the first path 16, and to control the selective contraction of the SMA wires 25 in the second group so as to move the third portion 18 by an amount Δ2 relative to the second portion 15 along the second path 19. In this manner, the movement may be controlled relative to a first axis and a second axis aligned along the first path 16 and the second path 19, respectively. Alternatively, the controller 7 may be configured to control the selective contraction of the shape memory alloy wires 21 in the first group and the shape memory alloy wires 25 in the second group so as to produce a desired overall movement of the third portion 18 relative to the first portion 4 by a first component Δx parallel to the x-axis and a second component Δy parallel to the y-axis. Each component Δx, Δy will include a combination of the movement along the first path 16 and the second path 19.

[0092] The controller 7 controls the contraction of the SMA wires 21 in the first group and the SMA wires 25 in the second group by controlling the drive signals supplied to the shape memory alloy wires 21, 25. The drive signals may be current controlled or voltage controlled. The drive signals may be generated using a resistive feedback control technique, such as described in WO 2014 / 076463A1.

[0093] Since the movements (Δ1 and Δ2) of the third portion 18 relative to the first portion 4 are substantially isolated along the first path 16 and the second path 19, this can simplify the drive signals required to control the first set of SMA wires 21 and the second set of SMA wires 25. First, this can help reduce crosstalk between the intended movements parallel to the first path 16 and the second path 19. In other words, the crosstalk between the two degrees of freedom of the third portion 18 relative to the first portion 4 is reduced.

[0094] Included in camera The first actuator assembly 14 may be incorporated into the camera in a number of different ways.

[0095] For example, the first actuator assembly 14 may include Figure 1 The camera 1 is shown in which the image sensor 6 is supported on the first part 4 and the lens holder 10 is supported on the third part 18. The first part 4 is connected to the cover 9 and serves as a fixed reference point relative to the camera 1.

[0096] However, the first actuator 14 can be incorporated into the camera in other ways. For example, another camera (not shown) can be similar to the camera 1, except that the second part 15 is fixed relative to the camera (not shown) (for example, relative to the cover 9). In this way, the image sensor 6 supported on the first part 4 and the lens holder 10 supported on the third part 18 can be independently moved relative to the optical axis O (parallel to the vertical axis z as shown in the figure).

[0097] Typically, for inclusion in a camera, any of the first part 4, the second part 15, or the third part 18 may support the image sensor 6, while one of the remaining pair of parts 4, 15, 18 supports at least one lens 11. Typically, any of the first part 4, the second part 15, or the third part 18 may be fixed relative to the camera. Fixed relative to the camera means that the part 4, 15, 18 in question is mechanically fixed and has no degrees of freedom relative to the rest of the camera. For example, any of the parts 4, 15, 18 that is fixed may be rigidly attached to (or integrally formed with) a hood 9, a housing (not shown), a frame (not shown), or an enclosure of the camera.

[0098] Although the first actuator assembly 14 has been described in which the shape memory alloy wires 21 in the first group are parallel, this is not required. In other examples, one or more SMA wires 21 in the first group can be arranged to be non-parallel to one, some, or all of the other SMA wires 21 in the first group. Similarly, one or more SMA wires 25 in the second group can be arranged to be non-parallel to one, some, or all of the other SMA wires 25 in the second group.

[0099] A first actuator assembly 14 has been described in which the first set of SMA wires 21 applies a net moment (torque) about the vertical axis z (offset by the first flexures 281, 282), and in which the second set of SMA wires 25 also applies a net moment about the vertical axis z (offset by the second flexures 311, 312). However, in other examples, the first set of SMA wires 21 and / or the second set of SMA wires 25 may be arranged such that a net moment is not provided and / or may be small (e.g., by including additional SMA wires 21, 25).

[0100] The first actuator assembly 14 has been described in which the first set of SMA wires 21 and the first flexure 28 have two-fold rotational symmetry, and the second set of SMA wires 25 and the second flexure 31 also have two-fold rotational symmetry. However, this is not required, and in other examples, the first set of SMA wires 21 and / or the second set of SMA wires 25 and the corresponding flexures 28, 32 may be configured without rotational symmetry.

[0101] The first actuator assembly 14 has been described with respect to orthogonal x- and y-axes (or with respect to first and second orthogonal axes aligned along the first path 16 and the second path 19). However, this is not required, and in other examples, the edges 22 and / or the paths 16, 19 may be parallel to the first and second axes, which are arranged at any non-parallel angle to each other, such as any angle between 10° and 90°. The first actuator assembly 14 has been described with respect to the first paths 16 and 19, which are substantially straight and orthogonal. However, this is not required, and in other examples, the first path 16 and the second path 19 may be arranged at any non-parallel angle to each other, such as any angle between 10° and 90°.

[0102] The first path 16 and / or the second path 19 need not be straight, and in other examples, either or both of the paths 16, 19 may be curved (even for small displacements). When the first path 16 is not straight, if all points along the first path 16 form a range θ with the SMA wires 21 in the first group, min to θ max If the angle of the second part 15 is within the range of movement of the first part 4, it can be considered that the SMA wire 21 and the first path 16 form an angle within the range θ min to θ max Similarly, when the second path 19 is not straight, if all points along the second path 19 form an angle with the SMA wire 25 in the second group within the range θ min to θ maxIf the angle between the third part 18 and the second part 15 is within the range of movement of the third part 18 relative to the second part 15, it can be considered that the SMA wire 25 and the second path 19 form an angle within the range θ min to θ max The inner angle.

[0103] A first actuator assembly 14 has been described in which the constraints of the second portion 15 and the third portion 18 to the respective paths 16, 19 are provided by the relative flexures 28, 31. Since the paths 16, 19 are not parallel to the SMA wires 21, 25, amplification is provided. However, in other examples, the constraints of the SMA wires 21, 25 resulting in amplification and / or the constraints of the movement along the paths 16, 19 may be provided by one or more alternative elastic elements (e.g., springs, etc.). Alternatively, the constraints may be provided by one or more bearings (e.g., roller bearings as in FIG. 5). In further examples, the constraints resulting in amplification and / or the limitation of the movement to the paths 16, 19 may be provided by a combination of two or more elements selected from the respective first / second groups of relative shape memory alloy wires, one or more elastic elements, one or more springs, one or more flexures, and one or more bearings.

[0104] The sides 22 of the first actuator assembly 14 form a square shape, however this is not required. In other examples, the sides of the actuator assembly can form other shapes, such as, for example, a rectangle, a diamond, a kite, or any other regular or irregular trapezoid. In still other examples, the actuator assembly can have more or less than four sides, such as three, five, six, or eight sides.

[0105] In the first actuator assembly 14, the third portion 18 is substantially coplanar with the second portion 15 and is received within the second portion 15. However, in other examples, the third portion 18 may be stacked above the second portion 15 (along the vertical axis z) and substantially coextensive with the second portion 15 (see, e.g., FIG. 4 ).

[0106] In the first actuator assembly 14, each SMA wire 21 in the first group is fixed at one end to the second portion 15 and at the other end to the first portion 4, while each SMA wire 25 in the second group is fixed at one end to the third portion 18 and at the other end to the second portion 15. However, in other implementations, each SMA wire 21 in the first group may be fixed to the second portion 15 at one or more points along its length and to the first portion 2 at one or more points along its length, while each SMA wire 25 in the second group is fixed to the third portion 18 at one or more points along its length and to the second portion 15 at one or more points along its length.

[0107] Each SMA wire 21 in the first group preferably has a span length between the attachment points (or fixed points / end points) that is at least 80% of the side length of the second portion 15. Additionally or alternatively, each SMA wire 25 in the second group preferably has a span length between the attachment points (or fixed points / end points) that is at least 80% of the side length of the third portion 18. Preferably, each SMA wire 21, 25 comprises a single span. In other words, preferably, no SMA wire 21, 25 is hooked or looped on any element to cause a change in direction between the fixed points / end points. For example, when viewed perpendicular to the first plane 17 / second plane 20, none of the SMA wires 21, 25 is configured in a V-shape.

[0108] In the first actuator assembly 14, the first group of SMA wires 21 is composed of two SMA wires 211, 212, each having a single straight span. Similarly, the second group of SMA wires 25 is composed of two SMA wires 251, 252, each having a single straight span. However, in other examples, either or both of the first and second groups may include more than two SMA wires 21, 25, each having a single straight span.

[0109] In the first actuator assembly 14, each first flexure 28 connects the corresponding edge of the second portion 15 to the first portion 4. Typically, each first flexure 28 can form an angle between 0° and 45°, preferably between 0° and 20°, and further preferably between 0° and 10° with the corresponding edge of the second portion 15. In the first actuator assembly 14, each SMA wire 21 of the first group connects the corresponding edge of the second portion 15 to the first portion 4. Typically, each SMA wire 21 of the first group can form an angle between 0° and 45°, preferably between 0° and 20°, and further preferably between 0° and 10° with the corresponding edge of the second portion 15. The first flexure 28 connected to the same edge of the second portion 15 and the SMA wires 21 in the first group (for example, Figure 2 The SMA wire 211 and the first flexure 281 in the embodiment may form an angle between 13° and 45° with each other.

[0110] In the first actuator assembly 14, each second flexure 31 connects the corresponding edge of the third portion 18 to the second portion 15. Generally, each second flexure 31 can form an angle between 0° and 45° with the corresponding edge of the third portion 18, preferably an angle between 0° and 20°, and further preferably an angle between 0° and 10°. In the first actuator assembly 14, each SMA wire 25 of the second group connects the corresponding edge of the third portion 18 to the second portion 15. Each SMA wire 25 of the second group can form an angle between 0° and 45°, preferably an angle between 0° and 20°, and further preferably an angle between 0° and 10° with the corresponding edge of the third portion 18. The second flexure 31 connected to the same edge of the third portion 18 and the SMA wire 25 in the second group (e.g., SMA wire 312 and second flexure 312) can form an angle between 13° and 45° with each other.

[0111] In the first actuator assembly 14, the first flexure 28 is axially loaded in tension in response to actuation of the first set of SMA wires 21, and similarly the second flexure 31 is axially loaded in tension in response to actuation of the second set of SMA wires 25. In other examples, some or all of the first flexures 28 or the second flexures 31 may be arranged to be axially loaded in compression in response to actuation of the respective set of SMA wires 21, 25. When the flexures 28, 31 are loaded in compression, the design of the flexures should take into account the need to prevent buckling.

[0112] In the first actuator assembly 14, the first plane 17 and the second plane 20 are coplanar, and the second portion 15 surrounds the third portion 18. In other examples, the third portion 18 may alternatively surround the second portion 15. In other examples, the first plane 17 and the second plane 20 may alternatively be parallel, but offset from each other along the vertical direction z. For example, any or all of the first portion, the second portion, and the third portion may be stacked sequentially along the vertical direction z perpendicular to the first plane 17 and the second plane 20.

[0113] Second Exemplary Actuator Assembly Also refer to 4A to 4D , a second exemplary actuator assembly 39 (hereinafter referred to as “second actuator assembly”) is shown.

[0114] 4A to 4D Each of the EMBODIMENTS 1 and 2 shows all or part of the second actuator assembly 39 as viewed from below (along the vertical axis z). Figure 4A The third portion 18, the second flexure 31 and the second set of SMA wires are shown. Figure 4B Shows Figure 4A All the content in , plus part 2 15. Figure 4C Shows Figure 4B, and adds a first flexure 28 and a first set of SMA wires 21 . Figure 4D Shows Figure 4C , and added part 14.

[0115] The second actuator assembly 39 is identical to the first actuator assembly 14, except that the first portion 4, the second portion 15, and the third portion 18 are configured differently, as are the SMA wires 21, 25 and the flexures 28, 31 connecting therebetween. Only those portions of the second actuator assembly 39 that differ from the first actuator assembly 14 are described in detail below.

[0116] Specific reference Figure 4A , the third portion 18 is in the form of a thin, flat, rectangular plate having sides aligned with the x-axis and the y-axis. The second flexures 311, 312 are fixed to the underside of the third portion 14 (relative to the vertical direction z) and are oriented substantially diagonally to maximize the length of each second flexure 311, 312. Each second flexure 311, 312 extends between a first attachment tab 401, 402 fixed to the third portion 18 (or formed as part of the third portion 18) and a second attachment tab 411, 412 for fixing to the second portion 15. In addition to their lateral extension, each second flexure 311, 312 also extends slightly downward from the underside of the third portion 18 so that when there is no stress, the second attachment tab 411, 412 is located below the first attachment tab 401, 402. The SMA wires 251, 252 in the second set are fixed (e.g., crimped) to the first attachment tabs 401, 402 and extend in the same direction but at an angle to the corresponding second flexures 311, 312. Therefore, the second flexures 311, 312 are compressively loaded when the SMA wires 251, 252 in the second set are actuated.

[0117] Specific reference Figure 4B , the second portion 15 takes the form of a thin, flat, generally "H"-shaped plate including a first member 42 and a second member 43 extending generally along the short sides of the rectangular footprint of the third portion 18 and connected by a rigid connecting rod 44. The first and second members 42, 43 and the rigid connecting rod 44 are preferably formed as a single piece (e.g., stamped from sheet metal), but may alternatively be formed as separate components and attached together (e.g., welded).

[0118] The first attachment tab 401 corresponding to the first SMA wire 251 in the second group is attached to the upper surface of the first member 42, near the connection with the connecting rod 44, and the first SMA wire 251 in the second group is fixed (e.g., crimped) to the upper surface of the first member 42 at (or close to) the maximum extension of the first member 42 in the negative direction of the y-axis. The first attachment tab 402 corresponding to the second SMA wire 252 in the second group is attached to the upper surface of the second member 43, near the connection with the connecting rod 44, and the second SMA wire 251 in the second group is fixed (e.g., crimped) to the upper surface of the first member 42 at (or close to) the maximum extension of the first member 42 in the positive direction of the y-axis.

[0119] Specific reference Figure 4C and Figure 4D , the first portion 4 takes the form of a thin flat ring with rectangular inner and outer edges. The first flexures 281, 282 and the first set of SMA wires 211, 212 are connected to the underside of the second portion 15. Each first flexure 281, 282 has a corresponding attachment tab 451, 452, which is fixed to or formed integrally with the second portion 15, and the opposite end is directly fixed to the first portion 4 (e.g., its upper surface or inner edge) (or formed integrally therewith). Each SMA wire 211, 212 of the first set is fixed (e.g., crimped) at one end to a corresponding one of the attachment tabs 451, 452 of the first flexure 281, 282, and fixed to the first portion 4 at the opposite end.

[0120] An attachment tab 451 corresponding to the first SMA wire 211 in the first group is fixed to the end of the first member 42 opposite the first SMA wire 251 in the second group. Similarly, an attachment tab 452 corresponding to the second SMA wire 212 in the first group is fixed to the end of the second member 43 opposite the second SMA wire 252 in the second group.

[0121] The first flexures 281, 282 are generally parallel to each other and perpendicular to the second flexures 311, 312 (which are also generally parallel to each other). The first set of SMA wires 211, 212 are generally parallel to each other and perpendicular to the second set of SMA wires 251, 252 (which are also generally parallel to each other).

[0122] The first flexures 281, 282 may be oriented downward in a stress-free state so that the first portion 4 and the second portion 15 are in a state of equilibrium offset from each other along the vertical direction z. Alternatively, the first flexures 281, 282 need not be directed downward, and the second portion 15 may be substantially coplanar with the first portion 4 and disposed within a hole in the first portion 4. When the first portion 4 and the second portion 15 are offset from each other along the vertical direction z, the first portion 4 may alternatively take the form of a flat, thin rectangular plate (i.e., the hole may be omitted).

[0123] Another way to view the second actuator assembly 39 is that the third portion 18 has a first (upper) surface and a second (lower) surface, the second (lower) surface being opposite the first portion 4 across a gap in the vertical direction z and through which the SMA wires 21, 25 belonging to the first and second groups are routed. In the second actuator assembly 39, the first flexure 28 and the second flexure 31 are also routed through the gap between the first portion 4 and the second (lower) surface of the third portion 18 in the vertical direction z.

[0124] In this way, by routing the SMA wires 21, 25 and constraining the flexures 28, 31 behind the third portion 18 (through the space formed between the first portion 4 and the third portion 18), the length of the SMA wires 21, 25, and therefore the maximum stroke of the second actuator assembly 39, can be increased without increasing the lateral (xy plane) footprint of the second actuator assembly 39.

[0125] The rectangular shape of the second actuator assembly 39 may be particularly suitable for cameras using a periscope configuration. However, the overall shape of the second actuator assembly 39 may be modified to any shape described with respect to the first actuator assembly 14, such as a square. Generally, any feature or function described with respect to the first actuator assembly 14 is also applicable to the second actuator assembly 39 (e.g., combinable with the second actuator assembly 39) in the absence of technical incompatibilities.

[0126] When incorporated into a camera (e.g., camera 1), the lens assembly 3 may be fixed relative to the first portion 4 (or coupled via an actuator that provides relative movement in the vertical direction z), while the image sensor 6 is mounted to the upper surface of the third portion 18. This allows lateral movement between the image sensor 6 and the lens 11 for OIS functionality.

[0127] Third Exemplary Actuator Assembly Also refer to FIG. 5A to FIG. 5C , a third exemplary actuator assembly 46 (hereinafter referred to as the “third actuator assembly”) is shown.

[0128] Figure 5A A plan view of the third actuator assembly 46 is shown. Figure 5B Shown along Figure 5A Cross section along the line marked AA* in . Figure 5C Shown along Figure 5A Cross section of the line marked BB* in .

[0129] The second actuator assembly 39 is identical to the first actuator assembly 14, except that the constraint of the second portion 15 to move relative to the first portion 4 along the first path 16 and the constraint of the third portion 18 to move relative to the second portion 15 along the second path 19 are provided by respective roller bearings rather than flexures 28, 31. Only those portions of the third actuator assembly 46 that differ from the first actuator assembly 14 are described in detail below.

[0130] The first roller bearings 471, 472 couple the second portion 15 to the first portion 4 and constrain movement about the first path 16. The second roller bearings 481, 482 couple the third portion 18 to the second portion 15 and constrain movement about the second path 19.

[0131] Specific reference Figure 5B , each of the first roller supports 471, 472 includes a ball support 49 held in a ball support race formed between first grooves 501, 502 formed in the upper (relative to the vertical direction z) surface of the first portion 4 and slots 511, 512 formed in the second portion 15. The ball support race thus formed extends parallel to the first path 16 and at least partially defines the first path 16. Protrusions 521, 522, which partially expand the width of the second portion 15 around the slots 511, 512, may be included to enable the length of the ball support race of the first roller supports 471, 472 to be extended.

[0132] The second roller bearings 481, 482 have a different structure than the first roller bearings 471, 472, as the intention is to constrain and guide movement relative to the second portion 15 rather than the first portion. Figure 5C, each of the second roller supports 481, 482 includes a ball support 49 retained in a ball support race formed between slots 531, 532 formed in the third portion 18 and slots 541, 542 formed in overhanging extensions 551, 552 of the second portion 15. The ball support races so formed extend parallel to the second path 19 and actually define the second path 19. Each overhanging extension 551, 552 extends inwardly from an inner edge of the second portion 15 and is offset above the third portion 18 by an angled connecting portion 561, 562. Near the second roller supports 481, 482, the second portion 15 may be offset outwardly away from the third portion 18 by a respective kinked segment 571, 572. The overhanging extensions 551, 552 may extend inwardly from the inner edges of the respective kinked portions 571, 572, as shown in FIG. FIG. 5A to FIG. 5C The third portion 18 may include protrusions 581, 582 that expand into the space provided by the kinked portions 571, 572 so as to be able to extend the length of the corresponding ball bearing race.

[0133] Other variants It will be appreciated that many other variations of the embodiments described above are possible.

[0134] The first to third actuator assemblies 14 to 46 include two SMA wires 21, 25 in each of the first and second groups. However, more or fewer SMA wires 21, 25 may be used in one or both of the first and second groups.

[0135] For example, the contraction of each SMA wire 21 in the first group can be opposed by one or more springs coupling the first portion 4 to the second portion 15. For example, in the first actuator assembly 14 or the second actuator assembly 39, the second SMA wire 212 in the first group can be omitted. Then, one extreme of the range of motion along the first path 16 will be the equilibrium position of the flexure, and the other extreme will correspond to the maximum amplified travel of the first SMA wire 211 along the first path 16. In the third actuator assembly 46, the second SMA wire 212 in the first group can be replaced by a spring (of any form, including a flexure). In a similar manner, the contraction of each SMA wire 25 in the second group can be opposed by one or more springs coupling the second portion 15 to the third portion 18. At least, the first group of SMA wires 21 can include a single SMA wire 21, and the second group of SMA wires 25 can include a single SMA wire 25, each SMA wire being opposed by one or more corresponding springs, flexures, etc. The spring (opposing any SMA wires 21 , 25 ) may take the form of a coil spring, a flat spring, a leaf spring, a flexure, an element formed from an elastomeric material, or the like.

[0136] One or more of the first plane 17 and the second plane 20 need not be parallel to one or both of the other planes. One or more of the first plane 17 and the second plane 20 need not be perpendicular to the vertical axis z.

[0137] The actuator assembly 2, 14, 36, 39, 46 or a portion 4, 15, 18 thereof need not be configured to support a lens assembly and may, for example, be configured to support another type of optical element, an image sensor, etc. The portion 4, 15, 18 may or may not include the hole 34. The actuator assembly 2, 14, 39, 46 does not have to be used in a camera.

[0138] The vertical axis z does not necessarily correspond to the optical axis O. The vertical axis z may correspond to a line perpendicular to a plane defined by the flat surfaces of the first part 4, the second part 15 and / or the third part 18. The vertical axis z may correspond to a line perpendicular to a plane defined by the movement direction of the second part 15 and / or the third part 18 along the respective paths 16, 19.

[0139] The actuator assembly may include additional portions, such as a fourth portion, a fifth portion, etc. (not shown). Such additional portions may be constrained to move along additional paths (third, fourth, etc.) under the control of additional sets of SMA wires (not shown). The additional portions may be configured and / or constrained in any manner described herein with respect to the first portion 4, the second portion 15, and / or the third portion 18. The additional paths may be aligned with the first path 16 and / or the second path 19, or may be defined to not coincide with either of the first path 16 and the second path 19.

[0140] The actuator assembly 2, 14, 39, 46 may be or may be arranged in any of the following devices: a smartphone, a protective cover or case for a smartphone, a functional cover or case for a smartphone or electronic device, a camera, a foldable smartphone, a camera of a foldable smartphone, a foldable consumer electronic device, a camera with folded optics, an image capture device, an array camera, a three-dimensional sensing device or system, a servo motor, a consumer electronic device, a mobile or portable computing device, a mobile or portable electronic device, a laptop, a tablet computing device, an e-reader, a computing accessory or computing peripheral device, an audio device, a security system, a gaming system, a gaming accessory, a robot or robotic device, a medical device, an augmented reality system, an augmented reality device, a virtual reality system, a virtual reality device, a wearable device, a drone, an aircraft, a spacecraft, a submersible, a vehicle, an autonomous vehicle, a tool, a surgical tool, a remote control, a garment, a switch, a dial or button, a display screen, a touch screen, a flexible surface, and a wireless communication device. It will be understood that this is a non-exhaustive list of example devices.

Claims

1. An actuator assembly, comprising: Part I; a second portion constrained to move along a first path in a first plane relative to the first portion; a first set of one or more shape memory alloy wires configured to move the second portion along the first path, the first set of shape memory alloy wires being arranged such that movement of the second portion is amplified relative to a corresponding change in length of the first set of shape memory alloy wires; a third portion constrained to move along a second path relative to the second portion in a second plane, the second plane being parallel to or coplanar with the first plane, and the second path being non-parallel to the first path; and A second set of one or more shape memory alloy wires is configured to move the third portion along the second path, the second set of shape memory alloy wires being arranged such that movement of the third portion is amplified relative to a corresponding change in length of the second set of shape memory alloy wires.

2. The actuator assembly according to claim 1, wherein: Each shape memory alloy wire of the first set of shape memory alloy wires has a span length between attachment points that is at least 80% of a side length of the second portion; and / or Wherein, each shape memory alloy wire of the second group of shape memory alloy wires has a span length between attachment points that is at least 80% of a side length of the third portion.

3. The actuator assembly according to claim 1 or 2, wherein: Each shape memory alloy wire of the first set of shape memory alloy wires comprises a single span; and / or Wherein each shape memory alloy wire in the second set of shape memory alloy wires comprises a single span.

4. An actuator assembly according to any one of claims 1 to 5, wherein: The first group of shape memory alloy wires consists of two shape memory alloy wires, each shape memory alloy wire in the first group of shape memory alloy wires comprises a single straight span; and / or, Wherein, the second group of shape memory alloy wires consists of two shape memory alloy wires, and each shape memory alloy wire in the second group of shape memory alloy wires includes a single straight span.

5. An actuator assembly according to any one of claims 1 to 7, wherein: Each shape memory alloy wire in the first group of shape memory alloy wires forms an angle between 45° and 77°, inclusive, with the first path; and / or Wherein, each shape memory alloy wire in the second group of shape memory alloy wires forms an angle between 45° and 77° with the second path, including endpoints.

6. An actuator assembly according to any one of claims 1 to 5, wherein: The constraint of the second portion on the first path comprises one or more first flexures; and / or The constraint of the third part on the second path includes one or more second flexures.

7. The actuator assembly according to claim 6, wherein: Each first flexure is axially loaded in response to actuation of the first set of shape memory alloy wires; and / or Wherein each second flexure is axially loaded in response to actuation of the second set of shape memory alloy wires.

8. The actuator assembly according to any one of claims 1 to 7, further comprising a controller configured to control the selective contraction of the shape memory alloy wires in the first group of shape memory alloy wires to move the second part along the first path relative to the first part, and to control the selective contraction of the shape memory alloy wires in the second group of shape memory alloy wires to move the third part along the second path relative to the second part.

9. The shape memory alloy actuator assembly according to any one of claims 1 to 8, wherein: The constraint of the second portion on the first path includes one or more first roller bearings; and / or Wherein, the constraint of the third portion on the second path includes one or more second roller supports.

10. The shape memory alloy actuator according to any one of claims 1 to 9, wherein: contraction of each shape memory alloy wire in the first set of shape memory alloy wires is opposed by one or more other shape memory alloy wires in the first set of shape memory alloy wires; and / or wherein contraction of each shape memory alloy wire in the second group of shape memory alloy wires is opposed by one or more other shape memory alloy wires in the second group of shape memory alloy wires.

11. The shape memory alloy actuator according to any one of claims 1 to 10, wherein: The first plane and the second plane are coplanar.

12. The shape memory alloy actuator according to claim 11, wherein: The second portion surrounds the third portion.

13. The shape memory alloy actuator according to any one of claims 1 to 10, wherein: The first plane and the second plane are parallel, and wherein the first portion, the second portion and the third portion are stacked in sequence along a vertical direction perpendicular to the first plane and the second plane.

14. The shape memory alloy actuator according to any one of claims 1 to 13, wherein: The third portion includes a central hole, wherein no shape memory alloy wire passes through the central hole.

15. The shape memory alloy actuator according to any one of claims 1 to 13, wherein: The third portion has a first surface and a second surface, the second surface being opposite to the first portion across the gap; wherein a shape memory alloy wire belonging to the first group of shape memory alloy wires is routed through the gap; and / or Wherein, the shape memory alloy wire belonging to the second group of shape memory alloy wires is routed through the gap.

16. A shape memory alloy actuator according to any one of claims 2 to 13 when dependent on claim 6, wherein: The third portion has a first surface and a second surface, the second surface being opposite to the first portion across the gap; wherein at least one first flexure is routed through the gap; and / or Wherein, at least one second flexure is routed through the gap.

17. A method for controlling a shape memory alloy actuator according to any one of claims 1 to 16, comprising: controlling the second portion to move relative to the first portion along the first path in the first plane; The third portion is controlled to move along the second path relative to the second portion in the second plane.

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