CN116472487A

CN116472487A - SMA actuator assembly

Info

Publication number: CN116472487A
Application number: CN202180078416.3A
Authority: CN
Inventors: 詹姆斯·豪沃思; 罗宾·爱丁顿
Original assignee: Cambridge Mechatronics Ltd
Current assignee: Cambridge Mechatronics Ltd
Priority date: 2020-11-23
Filing date: 2021-11-23
Publication date: 2023-07-21
Also published as: WO2022106856A1; GB2601306A; GB202018374D0; GB2601306B

Abstract

A Shape Memory Alloy (SMA) actuator assembly comprising: a support structure; a movable member movable within a range of movement in a plane relative to the support structure; an anti-rotation mechanism configured to limit rotation of the movable component relative to the support structure about any axis perpendicular to the plane; and a total of three SMA wires, which are individually controllable to move the movable part to any position within said range of movement relative to the support structure.

Description

SMA actuator assembly

The present invention relates to the use of Shape Memory Alloy (SMA) wires to provide positional control of a movable component supported on a support structure.

There are various types of actuator assemblies in which it is desirable to provide positional control of a movable member. SMA wires are advantageous as actuators in such actuator assemblies, particularly due to the high energy density of SMA wires, which means that the SMA wires required to apply a given force have relatively small dimensions.

One type of actuator assembly in which SMA wires are known to be used as actuators is a camera (particularly a miniature camera). The actuator assembly may for example be used to provide Optical Image Stabilization (OIS) in such a camera. WO 2013/175197 A1 discloses an SMA actuator assembly in which a total of four SMA wires are used to provide OIS by moving a movable lens element in two orthogonal directions to any position within a range of movement relative to an image sensor on a support structure without applying any net torque to the movable part. WO 2017/072535 A1 discloses an SMA actuator assembly wherein SMA wires are used to provide OIS by moving a movable image sensor relative to a lens element.

The present invention relates to providing an alternative SMA actuator assembly for moving a movable part in a plane relative to a support structure, for example for the purpose of providing OIS.

According to the present invention, there is provided a Shape Memory Alloy (SMA) actuator assembly comprising: a support structure; a movable member movable within a range of movement in a plane relative to the support structure; an anti-rotation mechanism (anti-rotation mechanism) configured to limit rotation of the movable component relative to the support structure about any axis perpendicular to the plane; and a total of three SMA wires that are individually controllable to move the movable part relative to the support structure to any position within said range of movement.

Providing an anti-rotation mechanism in combination with three SMA wires allows three degrees of freedom of the movable part to be controlled: movement along the x-axis, movement along the y-axis, and tension in the SMA wire. The anti-rotation mechanism limits rotation of the movable component such that any torque applied by the SMA wire to the movable component is converted into translational movement and/or tension in the SMA wire. Controlling the tension allows for more precise control of the SMA wire than assemblies that do not provide such tension control. Thus, the SMA actuator assembly is capable of precisely and controllably moving a movable part within a plane of movement, for example for the purpose of providing OIS.

According to the present invention, there is also provided a Shape Memory Alloy (SMA) actuator assembly comprising: a support structure; a movable member movable in a plane relative to the support structure; an anti-rotation mechanism configured to limit rotation of the movable component relative to the support structure about any axis perpendicular to the plane; a total of two SMA wires, wherein none of the SMA wires is collinear, and wherein the SMA wires are individually controllable to apply a force to the movable part in two directions in a plane; and a biasing arrangement configured to apply a force to the movable component that is opposite to a force applied by the two SMA wires.

Providing an anti-rotation mechanism in combination with two SMA wires allows two degrees of freedom of the movable part to be controlled: movement along the x-axis and movement along the y-axis. The anti-rotation mechanism limits rotation of the movable component such that any torque applied to the movable component by the SMA wire is converted into translational movement. The biasing arrangement opposes the force applied by the two SMA wires and thus may move the movable member in a direction opposite to the direction in which the two SMA wires move the movable member. Thus, the SMA actuator assembly is capable of controllably moving a movable part within a plane of movement, for example for the purpose of providing OIS.

According to the present invention there is also provided a camera device comprising an SMA actuator assembly and an image sensor fixed relative to a support structure. The movable component includes a lens assembly including one or more lenses configured to focus an image on the image sensor. The SMA actuator assembly may be used to provide OIS in a camera device by moving the lens assembly transverse to the optical axis. The overall size of the camera device may be reduced compared to a camera providing OIS by tilting the camera unit or image sensor, wherein the camera device requires additional clearance in the z-direction to allow such tilting.

Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:

FIG. 1a is a schematic side view of a camera device incorporating an SMA actuator assembly;

FIG. 1b is a schematic plan view of an SMA actuator assembly according to an embodiment of the present invention;

FIG. 2a is a schematic plan view of a bearing arrangement and anti-rotation mechanism in an SMA actuator assembly according to an embodiment of the present invention;

FIG. 2b is a schematic plan view of another bearing arrangement and anti-rotation mechanism in an SMA actuator assembly according to an embodiment of the present invention;

FIG. 3a is a schematic plan view of an arrangement of SMA wires in an SMA actuator assembly according to an embodiment of the present invention;

FIG. 3b is a schematic plan view of another arrangement of SMA wires in an SMA actuator assembly according to an embodiment of the present invention;

3 c-3 e are schematic plan views of intermediate elements that may be included in the SMA actuator assembly of FIG. 3 b;

FIG. 3f is a schematic plan view of another arrangement of SMA wires in an SMA actuator assembly according to an embodiment of the present invention;

FIG. 4a is a schematic plan view of another SMA actuator assembly according to an embodiment of the present invention; and

figure 4b is a schematic plan view of another SMA actuator assembly according to an embodiment of the invention.

In the following description, the present invention will be described with reference to a camera in which OIS is desired. However, this is one non-limiting exemplary use of the present invention, and it will be appreciated that the present invention may be used in any optical system or non-optical system, and for any purpose. For example, the present invention may be used to improve the performance of a system for performing 3D sensing (i.e., generating a 3D representation of a scene) or in haptic applications.

Fig. 1a schematically shows a camera device 1 according to the invention comprising an SMA actuator assembly 2. The camera apparatus 1 will be comprised in a portable electronic device such as a mobile phone or a tablet computer. Miniaturization is therefore an important design criterion.

The SMA actuator assembly 2 comprises a support structure 10 and a movable part 20. The movable part 20 is supported on the support structure 10. The movable part 20 is movable in a range of motion in a plane (in particular in the x-y plane) with respect to the support structure 10. Movement in a direction perpendicular to the plane (i.e., along the z-axis) may be limited or prevented.

The SMA actuator assembly 2 includes a plurality of SMA wires 30. The SMA wire 30 may be connected under tension between the support structure 10 and the movable part 20. The SMA wire 30 may be connected to the support structure 10 and/or the movable part 20 at the ends of the SMA wire 30 using a connection element 33, such as a crimp connection. The crimp connection may crimp the SMA wire to mechanically retain the SMA wire and provide an electrical connection to the SMA wire 30. However, any other suitable connection may alternatively be used. The SMA wire 30, when selectively contracted, is capable of driving the movable part 20 to move relative to the support structure 10 in translational movement with two degrees of freedom (i.e. along the x-axis and the y-axis).

The movable part 20 may be supported on the support structure 10 (and thus suspended from the support structure 10) solely by the SMA wires 30. Preferably, however, the SMA actuator assembly 2 comprises a bearing arrangement 40 that supports the movable part on the support structure 10. The bearing arrangement 40 may have any suitable form that allows the movable part 20 to move in the x-y plane relative to the support structure 10. For this purpose, the bearing arrangement 40 may for example comprise a rolling bearing, a flexible bearing (flex bearing) or a plain bearing (plain bearing). The bearing arrangement 40 may limit or prevent movement of the movable part 20 relative to the support structure 10 in the z-direction. The bearing arrangement 40 may limit movement in the x-y plane to a particular range of movement.

The camera device 1 further comprises a lens assembly 3 and an image sensor 4. The lens assembly 3 comprises one or more lenses configured to focus an image on the image sensor 4. The image sensor 4 captures an image and may be of any suitable type, such as a Charge Coupled Device (CCD) or CMOS device. The lens assembly 3 comprises a lens holder, for example in the form of a cylinder, supporting one or more lenses. One or more lenses may be fixed in a lens holder, or may be supported in the lens holder in such a way that at least one lens is movable along the optical axis O, for example to provide zooming or focusing (e.g. Auto Focus (AF)). The camera device 1 may be a miniature camera device in which the or each lens of the lens assembly 3 has a diameter of 20mm or less (preferably 12mm or less). For ease of reference, the z-axis is considered to be the optical axis O of the lens assembly 3, while the x-axis and the y-axis are perpendicular to the z-axis. In the desired orientation of the lens assembly 3, the optical axis O is perpendicular to the photosensitive area of the image sensor 4, while the x-axis and the y-axis are parallel to the photosensitive area of the image sensor 20.

In the embodiment shown in fig. 1a, the movable part 20 comprises a lens assembly 3. The image sensor 4 may be fixed relative to the support structure 10, i.e. mounted on the support structure 10. In other embodiments (not shown), the lens assembly 3 may be fixed (in the x-y plane) relative to the support structure 10, and the movable part 20 may comprise the image sensor 4. In either embodiment, in operation, the lens assembly 3 moves relative to the image sensor 4 in the x-y plane orthogonal to the optical axis O. This has the effect of moving the image on the image sensor 4. This is used to provide OIS to compensate for image movement of the camera device 1 caused by, for example, a user handshake.

The camera apparatus 1 includes a vibration sensor 6 and a control circuit 8. For example, the vibration sensor 6 may be a gyro sensor, but other types of vibration sensors 6 may be generally used. The vibration sensor 6 detects the vibration that the camera apparatus 1 is experiencing, and generates an output signal representing the vibration of the camera apparatus 1. The control circuit 8 may be implemented in an Integrated Circuit (IC) chip. The control circuit 8 generates a drive signal for the SMA wire 30 in response to the output signal of the vibration sensor 6. SMA materials have the property that upon heating they undergo a solid state phase change that causes the SMA material to contract. Thus, application of a drive signal to the SMA wire 30, thereby heating the SMA wire 30 by allowing current to flow, will cause the SMA wire 30 to contract and move the movable part 20. The drive signal is selected to drive the movement of the movable part 20 in such a manner that the image sensed by the image sensor 4 is stabilized. The control circuit 8 supplies the generated drive signal to the SMA wire 30, thereby providing OIS.

An actuator assembly with four SMA wires as in WO 2013/175197 A1 may be used to provide OIS. The four SMA wires allow control of the movable part 20, in particular control, in four degrees of freedom with respect to the support structure 10: movement along the x-axis, movement along the y-axis, rotation about the z-axis, and tension in the SMA wire. In some cases, it may not be necessary to control rotation about the z-axis. For example, without limiting the claimed invention, it may not be beneficial to allow the movable member 20 to rotate about the z-axis when the movable member 20 includes a lens assembly 3 having only rotationally symmetric lenses.

The inventors have found that providing an anti-rotation mechanism 7 that limits rotation about the z-axis allows a total of three SMA wires 30 to control: movement along the x-axis, movement along the y-axis, and tension in the SMA wire 30. The use of a total of three SMA wires 30 may reduce the cost and power consumption of the SMA actuator assembly 2 compared to an actuator assembly having four or more SMA wires, while allowing OIS in the camera apparatus 1.

Fig. 1b schematically depicts a plan view of an embodiment of the actuator assembly 2 with an anti-rotation mechanism 7 and a total of three SMA wires 30. A total of three SMA wires 30 consist of only three independently controllable SMA wires 30. The anti-rotation mechanism 7 limits the rotation of the movable part 20 with respect to the support structure 10 about any axis perpendicular to the plane. Thus, the rotation of the movable part 20 about the z-axis is limited, i.e. the rotation about the z-axis is hindered or even prevented. The three SMA wires 30 are individually controllable to move the movable part 20 to any position within the range of movement relative to the support structure 10. Thus, three SMA wires may reversibly and controllably move the movable part 20 in the x-y plane. This allows the movable member 20 to be moved to any x-y coordinate within the range of motion by controlling the SMA wire 30.

Each of the SMA wires 30 applies a respective force to the movable part 20 when contracted. The first SMA wire 30a applies a force in a first direction 31a (e.g., in the x-direction) in the x-y plane. The second SMA wire 30b applies a force in a second direction 31b (e.g., in the y-direction) in the x-y plane. As shown in fig. 1b, the first direction 31a and the second direction 31b may be orthogonal directions. However, in general, the first direction 31a and the second direction 31b may be any two different directions in the x-y plane, and thus may be two directions that are angled with respect to each other. The third SMA wire 30c applies a force in a third direction 31c in the x-y plane to the movable part 20 when contracted. The force in the third direction 31c is opposite to the force exerted by the first SMA wire 30a and/or the second SMA wire 30 b. Thus, the third direction 31c is opposite to the first direction 31a, or opposite to the second direction 31b, or opposite to any direction within an acute angle between the first direction 31a and the second direction 31 b. Preferably, the third direction 31c is opposite to the forces applied by both the first SMA wire 30a and the second SMA wire 30b, and thus is opposite to any direction within an angle between the first direction 31a and the second direction 31b (i.e., within a right angle, an acute angle, or an obtuse angle).

The three SMA wires 30 may each extend parallel to the x-y plane and may therefore apply a force to the movable part 20 only in the x-y plane. This is advantageous in minimizing the size of the SMA actuator assembly 2 in the z-direction. In some embodiments, the SMA wire 30 may be angled (i.e., inclined at a non-zero angle (preferably a small angle)) relative to the x-y plane, in which case the forces exerted by the SMA wire 30 in the first, second, and third directions refer to the components of the total force exerted by the SMA wire 30 acting in the x-y plane. This may be useful, for example, when the bearing arrangement 40 comprises a ball bearing, in which case the tension in the SMA wire 30 may be used to urge the bearing surfaces of the ball bearing together.

Fig. 2a and 2b schematically depict in plan view a bearing arrangement 40 comprising or incorporating an anti-rotation mechanism 7. The bearing arrangement 40 of fig. 2a and 2b limits the rotation of the movable part 20 relative to the support structure 10 about the z-axis. Each bearing arrangement 40 essentially comprises two bearing portions connected in mechanical series, each bearing portion allowing movement in a respective one of two non-collinear directions in the x-y plane.

Fig. 2a shows a bearing arrangement 40, which bearing arrangement 40 comprises an arrangement of flexure arms (flexarms) connected between the support structure 10 and the movable part 20. The bearing arrangement 40 comprises two pairs of flexure arms 41a, 42a connected in mechanical series. The first pair of flexure arms 41a allows movement in one of two orthogonal directions (e.g., in the x-direction) in the x-y plane. The first pair of flexure arms 41a restrict movement in any other direction. The second pair of flexure arms 42a allows movement in the other of the two orthogonal directions (e.g., in the y-direction) in the x-y plane. The second pair of flexure arms 42a limit movement in any other direction. Thus, in combination, the two pairs of flexure arms 41a, 42a allow movement in the x-y plane and limit rotation about the z-axis. The bearing arrangement 40 may be a single piece (single piece), so all parts of the bearing arrangement may be integrally formed, for example, from a sheet material such as sheet metal. The bearing arrangement 40 may be rigidly connected to the movable part 20 and the support structure 10, or may be integrally formed with (a part of) the support structure 10 and/or (a part of) the movable part 20.

Fig. 2b shows an alternative bearing arrangement 40, which bearing arrangement 40 comprises an arrangement of rolling bearings connected between the support structure 10 and the movable part 20. For example, the rolling bearing may be a ball bearing, a roller bearing or a rocker bearing (rock bearing). The rolling bearing may comprise rolling elements (e.g. balls, rollers or rockers) supported on two bearing surfaces. The bearing arrangement 40 comprises two rolling bearings 41b, 42b, which two rolling bearings 41b, 42b are arranged in mechanical series between the movable part 20 and the support structure 10. The first rolling bearing 41b allows movement in one of two orthogonal directions (e.g., in the x-direction) in the x-y plane. The first rolling bearing 41b restricts movement in any other direction. The first rolling bearing 41b may include rolling elements supported on the surface of the movable member 20 and the surface of the intermediate plate 43. The movable member 20 is movable in the x-direction relative to the intermediate plate 43. The second rolling bearing 42b allows movement in the other of the two orthogonal directions (e.g., in the y-direction) in the x-y plane. The second rolling bearing 42b restricts movement in any other direction. The second rolling bearing 42b may comprise rolling elements bearing on the surface of the support structure 10 and the surface of the intermediate plate 43. The intermediate plate 43 is movable in the y-direction relative to the support structure 10. Thus, in combination, the two rolling bearings 41b, 42b allow movement in the x-y plane and limit rotation about the z-axis.

Although fig. 2a and 2b show two examples of bearing arrangements 40 comprising an anti-rotation mechanism, it should be understood that the anti-rotation mechanism 7 may be separate from the bearing arrangement 40 or comprised in a different bearing arrangement 40. In general, the anti-rotation mechanism 7 may include any mechanism that limits rotation of the movable member 20 relative to the support structure 10. Further examples of such anti-rotation mechanisms 7 are disclosed in co-pending GB 2005570.3, which examples are incorporated herein by reference. Furthermore, as will be explained with reference to fig. 3d and 3e, the anti-rotation mechanism 7 may be comprised in a connection between the movable part 20 and the third SMA wire 30 c.

The SMA actuator assembly 2 may include a different bearing arrangement 40 than those described with respect to fig. 2a and 2b, such as a different type of flexure bearing or rolling bearing, or any type of sliding bearing, that allows movement in the x-y plane. The slide bearing comprises two bearing surfaces that bear against each other, so that the movable part 20 may comprise bearing surfaces that bear on complementary bearing surfaces of the support structure 10. In general, the bearing arrangement 40 may have any configuration that allows the movable member 20 to move in the x-y plane relative to the support structure 10.

The arrangement of the SMA wire 30 of fig. 1b may require a relatively large footprint (footprint) to achieve a given stroke or amount of movement of the movable part 20 relative to the support structure 10.

Fig. 3 a-3 f schematically depict in plan view the SMA actuator assembly 2 having a reduced footprint to achieve a given amount of travel. In each of these SMA actuator assemblies 2, each SMA wire 30 extends along an edge or side of the movable part 10. The SMA wires 30 are arranged in loops (loops) at different angular positions about the z-axis. Alternatively (not shown), some of the SMA wires 30 may extend toward the center of the movable component 10 to achieve a reduced footprint. In either case, the SMA wires 30 do not extend in a direction radially away from the movable part 20, and thus the gap between the movable part 20 and the support structure 10 in the x-y plane may be reduced, thereby reducing the total footprint of the SMA actuator assembly 2 in the x-y plane.

The SMA actuator assembly 2 of fig. 3 a-3 f may correspond to the SMA actuator assembly 2 described with respect to fig. 1a and 1b, except for the arrangement of SMA wires 30. In fig. 3 a-3 f, the first SMA wire 30a extends in the x-direction. The first SMA wire 30a applies a force to the movable part 20 in the x-direction and thus can move the movable part 20 in the x-direction. The second SMA wire 30b extends in the y-direction. The second SMA wire 30b applies a force to the movable part 20 in the y-direction and thus may move the movable part 20 in the y-direction. Thus, the first SMA wire 30a and the second SMA wire 30b apply a force to the movable part 20 in their extension direction. The first SMA wire 30a and the second SMA wire 30b may be connected to the movable part 20 to apply torque in alternating directions (in alternate sense) about the z-axis. For example, as shown in fig. 3a, the first SMA wire 30a may apply a counter-clockwise torque to the movable part 20, while the second SMA wire 30b may apply a clockwise torque to the movable part 20. Due to the provision of the anti-rotation mechanism 7, this torque will be (at least partly) converted into a translational movement in the x-direction and the y-direction.

The third SMA wire 30c also extends along an edge of the movable part 20. Thus, the third SMA wire 30c extends in a direction different from the third direction 31c, in which third direction 31 the third SMA wire 30c applies a force to the movable part 20. To redirect the tension in the third SMA wire 30c along the third direction 31c, the SMA actuator assembly 2 includes an intermediate element 35. The intermediate element 35 redirects the tension in the third SMA wire 30c to act in the third direction 31 c.

Fig. 3 a-3 f show different examples of intermediate elements 35. In the SMA actuator assembly 2 of fig. 3a, the intermediate element 35 comprises a flexure arm 35a. The flexible arm 35a is connected at one end to the support structure 10 and at the other end to the movable part 20. The flexible arm 35a allows the other end to move in the third direction 31c relative to the support structure 10. The third SMA wire 30c is connected to the flexible arm 35a, for example to one end of the flexible arm 35a connected to the movable part 10. Upon contraction, the third SMA wire 30c therefore deflects the flexure arm. This urges the other end of the flexible arm 35a in the third direction 31c and thus applies a force to the movable member 30 in the third direction 31 c.

In the SMA actuator assembly 2 of fig. 3 b-3 f, the third SMA wire 30c is bent around the contact area 36 with the intermediate element 35. Thus, the third SMA wire 30c includes two SMA portions extending in two directions at the contact area 36. The two SMA portions are angled with respect to each other. The two SMA portions are straight portions of SMA wire. In the example of fig. 3 b-3 f, one of the two portions extends along the x-axis and the other of the two portions extends along the y-axis. Thus, the two portions extend in different directions along the edge of the movable part 10. The intermediate element 35 is arranged between the third SMA wire 30c and the movable part 20. Thus, the intermediate element 35 extends from the contact area 36 to the movable part 20. Each portion of the third SMA wire 30c exerts a force on the contact area 36 in a different direction when contracted. In the depicted example, one of the two SMA portions applies a force in the x-direction and the other of the two SMA portions applies a force in the y-direction. The resultant force of the two parts, and thus the force exerted by the third SMA wire 30c, acts in a third direction 31 c.

The intermediate element 35 preferably allows the movable part 20 to move in the x-y plane relative to the contact area 36. This reduces the effect of the third SMA wire 30c on the movement of the movable part 20 in the x-y plane due to the forces applied by the first SMA wire 30a and the second SMA wire 30 b. For example, as shown in fig. 3b, the intermediate element 35 may comprise a flexing arm 37a. The flexing arm 37a extends substantially in the third direction 31 c. One end of the flexible arm 37a is connected to the movable member 20, and the other end of the flexible arm is connected to the contact area 36. The flexing arm 37a resists buckling (buckling) and thus transfers force from the third SMA wire 30c to the movable part 20 in the third direction 31 c. The flexing arm 37a allows the movable member 20 to move relative to the contact area 36 in a direction orthogonal to the third direction 31 c. The movable part 20 can thus move in the x-y plane due to the forces exerted by the first SMA wire 30a and the second SMA wire 30 b.

Fig. 3c shows another example of an intermediate element 35, which intermediate element 35 may replace the intermediate element 35 depicted in fig. 3 b. The intermediate element 35 comprises a rolling bearing 37b (e.g. a ball bearing, a roller bearing or a rocker bearing). The rolling bearing 37b comprises rolling elements (e.g. balls, rollers or rockers) located between two bearing surfaces. The first bearing surface is connected to the movable part 20. The second bearing surface is connected to the contact area 36. The two bearing surfaces extend substantially perpendicular to the third direction 31 c. The rolling bearing 37b allows the movable member 20 to move relative to the contact area 36 in a direction orthogonal to the third direction 31 c. The movable part 20 can thus move in the x-y plane due to the forces exerted by the first SMA wire 30a and the second SMA wire 30 b.

Fig. 3d and 3e show further examples of intermediate elements 35 that may replace the intermediate element 35 depicted in fig. 3 b. In fig. 3d and 3e, the intermediate element 35 comprises or contains an anti-rotation mechanism 7. Thus, the intermediate element 35 limits the rotation of the movable part 20 with respect to the support structure 10 about the z-axis. In particular, as shown in fig. 3d, the intermediate element 35 may comprise two flexing arms 37c. Each flexure arm extends between the contact region 36 and the movable member 20. The two flexure arms 37c extend substantially in the third direction 31 c. The two flexure arms 37c are spaced apart from each other in the x-y plane (in particular in a direction orthogonal to the third direction 31 c). Thus, the two flexure arms 37c allow the movable member 20 to move relative to the contact region 36 in any direction orthogonal to the third direction 31 c. Rotation of the movable member 20 about the z-axis relative to the contact region 36 is limited.

Alternatively, as shown in fig. 3e, the intermediate element 35 may comprise two rolling elements 37d. The two rolling elements 37d are arranged between a bearing surface connected to the contact area 36 and a bearing surface connected to the movable part 20. Two rolling elements 37d contact and are supported on these bearing surfaces. The two rolling elements 37d are spaced apart from each other in the x-y plane, in particular in a direction orthogonal to the third direction 31 c. Thus, the two rolling elements 37d prevent rotation of the two bearing surfaces relative to each other about the z-axis. This prevents rotation of the movable member 20 relative to the support structure 10 about the z-axis.

In the embodiment of fig. 3 a-3 e, the third SMA wire 30c is arranged on the opposite side of the movable part 20 from the first SMA wire 30a and the second SMA wire 30 b. Alternatively, the third SMA wire 30c may be arranged on the same side of the movable part as the first SMA wire 30c and the second SMA wire 30c, and thus typically on the same half (half) of the perimeter of the movable part as the first SMA wire 30c and the second SMA wire 30 c. An example of this is schematically depicted in plan view in fig. 3 f. The SMA actuator assembly 2 of fig. 3f substantially corresponds to the SMA actuator assembly 2 of fig. 3b except that three SMA wires 30 are arranged on the same half side of the perimeter of the movable part 20. This may reduce the space required in the other half of the perimeter of the movable part 20, allowing the movable part 20 to be located closer to the corner of any device (e.g. camera apparatus 1 or mobile phone or other device) in which the SMA actuator assembly 2 is to be incorporated. Although fig. 3f depicts only an example of the SMA actuator assembly 2 of fig. 3b (wherein three SMA wires are arranged on the same side), it should be understood that the SMA actuator assembly of any one of fig. 3 a-3 e may be modified in a similar manner to achieve a configuration wherein three SMA wires 30 are arranged on the same side.

The SMA actuator assembly 2 of fig. 1b and 3 a-3 f comprises a total of three SMA wires 30, allowing the following to be independently controlled: movement along the x-axis, movement along the y-axis, and tension in the SMA wire 30. In some applications, such as in devices that do not require precise and reliable positioning, it may not be necessary to control the tension in the SMA wire 30. In such an application, one of the three SMA wires 30 may be redundant, and a total of two SMA wires 30 may be used to independently control movement along the x-axis and movement along the y-axis. Such an SMA actuator assembly 2 may correspond to the SMA actuator assembly 2 described above, except that the third SMA wire 30c is replaced with a biasing arrangement 50.

Such an SMA actuator assembly 2 is schematically depicted in fig. 4a and 4 b. The SMA actuator assembly 2 includes a support structure 10 and a movable part 20, the movable part 20 being movable relative to the support structure 10 in the x-y plane. The SMA actuator assembly 2 also includes an anti-rotation mechanism that limits rotation of the movable part 20 relative to the support structure 10 about the z-axis. However, unlike what is described in relation to fig. 1b and 3 a-3 f, the SMA actuator assembly 2 includes a total of two SMA wires 30a, 30b. Neither SMA wire 30a, 30b is collinear. The SMA wires 30a, 30b are individually controllable to apply forces to the movable part 20 in two directions (e.g., two orthogonal directions) in the x-y plane. For example, the first SMA wire 30a may apply a force in the x-direction and the second SMA wire 30b may apply a force in the y-direction. The first SMA wire 30a and the second SMA wire 30b may extend along an edge of the movable part 20 or toward a center of the movable part 20.

Instead of the third SMA wire 30c, the SMA actuator assembly 2 comprises a biasing arrangement 50. The biasing arrangement 50 applies a force (biasing force) to the movable part 20 that is opposite to the force applied by the two SMA wires 30a, 30 b. The biasing arrangement 50 may be a spring or other resilient element. For example, as shown in fig. 4a, a spring or other resilient element is connected at one end to the support structure 10 and at the other end to the movable part 20. The spring or other resilient element may be arranged in the same manner as the third SMA wire 30c in fig. 1b and 3 a-3 f and biased to contract to apply a force in the third direction 31c in the manner described above. Alternatively, a spring or other resilient element may be biased to expand and be arranged in a substantially opposite manner to the third SMA wire 30c in fig. 1b and 3 a-3 f.

As shown in fig. 4b, the biasing arrangement 50 may also be incorporated into the bearing arrangement 40. Thus, the bearing arrangement 40 may support the movable part 20 on the support structure 10 in a manner that allows movement in the x-y plane and provide a biasing force that is opposite to the force applied by the first SMA wire 30a and the second SMA wire 30 b. For example, the bearing arrangement 40 may include one or more flexures connected between the support structure 10 and the movable member 20. One or more flexures may be pre-biased (preloaded) to apply a biasing force to movable member 20.

The SMA actuator assembly 2 of fig. 4b includes the bearing arrangement 40 described with respect to fig. 2 a. Thus, the bearing arrangement 40 may also serve as an anti-rotation mechanism 7. Thus, in the SMA actuator assembly 2 of fig. 4b, the purpose of the bearing arrangement 40 is to: i) Supporting the movable member 20 on the support structure 10 in a manner that allows movement in the x-y plane, ii) applying a biasing force to the movable member 20 that is opposite to the force applied by the two SMA wires 30a, 30b, and iii) restricting rotation of the movable member 20 relative to the support structure 10 about the z-axis. Providing a bearing arrangement 40 for all of these purposes may make the SMA actuator assembly more compact than an SMA actuator assembly in which these functions are implemented in separate components. However, according to the above disclosure, the anti-rotation mechanism 7 may be implemented in any other way (e.g. using the bearing arrangement 40 of fig. 2b, or by a suitable connection between the biasing arrangement 50 and the movable part 20 in the manner discussed in relation to fig. 3d and 3 e). Similarly, the biasing arrangement 50 may be implemented using a separate component from the bearing arrangement 40.

Fig. 5 schematically depicts an SMA actuator assembly 2 having an alternative arrangement of SMA wires 30 in a plan view in accordance with aspects of the invention. The SMA actuator assembly 2 comprises a support structure 10, a movable part 20, an anti-rotation mechanism 7 and three SMA wires 30 (e.g. as already described in relation to the embodiments of fig. 1b and 3 a-3 f).

As shown in fig. 3, at least one SMA wire 30 (preferably two SMA wires 30) may be disposed below the movable part 20. Thus, at least one SMA wire 30 (preferably two SMA wires 30) is disposed along the z-axis between the support structure 10 and the movable part 20. This may be particularly applicable in the case where an image sensor is provided on the movable member 20 instead of a lens. At least one SMA wire 30 (preferably two SMA wires 30) may extend diagonally under the movable part 20. At least one SMA wire 30 (preferably two SMA wires 30) may extend between two opposite corners of the movable part 20 (particularly when the movable part 20 has a rectangular or square cross-section). Arranging at least one SMA wire 30 below the substrate may reduce the footprint of the actuator assembly 2 in the x-y plane. The diagonally arranged at least one SMA wire 30 may increase the length of the SMA wire 30 without increasing the footprint of the actuator assembly compared to a case in which the SMA wires are not diagonally arranged.

In fig. 5, three SMA wires 30a, 30b, 30c are thus provided. Two SMA wires 30a, 30b are arranged diagonally below the movable part 20. The two SMA wires 30a, 30b are arranged perpendicular to each other. The two SMA wires 30a, 30b are arranged to apply forces in the same direction along a first axis (x-axis) and in opposite directions along a second axis (y-axis) perpendicular to the first axis. The third SMA wire 30c is arranged to apply a force along the first axis in a direction opposite to the force of the two SMA wires 30a, 30 b.

The embodiment of fig. 5 is only one example in which the SMA wire 30 is arranged below the movable part 20. Although not shown, many other arrangements of SMA wires 30 are possible. In some embodiments, and with reference to fig. 3a, for example, two SMA wires 30a, 30b may be arranged adjacent to the movable part 20 (as described with respect to fig. 3 a), and a third SMA wire 3c may extend diagonally below the movable part 20 (in particular in a direction along arrow 31c in fig. 3 a). Furthermore, in the embodiment of fig. 4a, one or both of the two SMA wires 30a, 30b may be arranged below the movable part 20, for example as described in relation to the SMA wires 30a, 30b of fig. 5.

Although the schematic plan views of the above figures show examples in which the movable member 20 has a square footprint in the x-y plane, it should be understood that the movable member 20 may generally have any other shape. For example, the movable part 20 may be substantially circular and follow the contour of, for example, a cylindrical lens holder. When referring to SMA wires 30 extending along edges or sides of the movable part 20, it is therefore not required that the SMA wires be parallel to such edges or sides. Rather, it is intended that the SMA wires 30 be arranged in a manner that allows the footprint of the SMA actuator assembly 2 in the x-y plane to be reduced as compared to the case in which the SMA wires 30 extend radially away from the optical axis O, while achieving a given amount of travel (i.e., movement of the movable component 20). In particular, the SMA wire 30 may extend in a manner similar to that depicted in the figures, regardless of the shape of the movable part 20 or the support structure 10.

It will be appreciated that the direction in which any of the SMA wires 30 described above applies force to the movable part 20 may vary to some extent as the movable part 20 moves relative to the support structure 10. The above description of the forces and the direction of the forces generally applies to the case in which the movable part 20 is in a central position with respect to the support structure 10, and therefore in a substantially central position in the movement envelope defined by the possible movements of the movable part 20 with respect to the support structure 10. The above description of the direction of the force and force may or may not remain applicable to being located at or towards the extreme end of the moving envelope (i.e. at the boundary of the moving envelope beyond which the movable part 20 may not move during normal operation). Normal operation refers to a situation in which the movable member 20 is moved due to a force applied by the SMA wire 30 and/or any optional biasing arrangement (e.g., for OIS purposes).

The term "shape memory alloy (SMA, shape memory alloy) wire" may refer to any element comprising SMA. The SMA wire may have any shape suitable for the purposes described herein. The SMA wire may be elongate and may have a circular cross-section or any other shape. The cross-section may vary along the length of the SMA wire. It is also possible that the length of the SMA wire (regardless of definition) may be similar to one or more of the other dimensions of the SMA wire. The SMA wire may be flexible or, in other words, flexible. In some examples, when connected in a straight line between two elements, the SMA wire may only apply tension that forces the two elements together. In other examples, the SMA wire may bend around the element and may apply a force to the element when the SMA wire tends to straighten under tension. The SMA wires may be beam-like or rigid and may be capable of applying different forces (e.g., non-tensile) to the element. The SMA wire may or may not include non-SMA material(s) and/or component(s). For example, the SMA wire may include a core of SMA and a coating of non-SMA material. Unless the context requires otherwise, the term "SMA wire" may refer to any configuration of SMA wire that acts as a single actuation element, e.g., the single actuation element may be independently controlled to generate a force acting on the element. For example, the SMA wire may comprise two or more portions of SMA wire arranged mechanically in parallel and/or in series. In some arrangements, the SMA wire may be part of a larger section of SMA wire (a larger piece of SMA wire). Such larger sections of SMA wire may comprise two or more portions that may be controlled separately, thereby forming two or more SMA wires.

It will be appreciated by those skilled in the art that while the foregoing has described what is considered to be the best mode of carrying out the disclosure and other modes of carrying out the disclosure where appropriate, the disclosure should not be limited to the specific configurations and methods disclosed in this description of the preferred embodiments. Those skilled in the art will recognize that the invention has a wide range of applications and that the embodiments can be modified in a wide range without departing from the scope of the claims.

Claims

1. A Shape Memory Alloy (SMA) actuator assembly comprising:

a support structure;

a movable member movable within a range of movement in a plane relative to the support structure;

an anti-rotation mechanism configured to limit rotation of the movable component relative to the support structure about any axis perpendicular to the plane; and

a total of three SMA wires that are individually controllable to move the movable part relative to the support structure to any position within the range of movement.

2. An SMA actuator assembly according to claim 1, wherein the first and second SMA wires are arranged to apply a force to the movable part in first and second directions, respectively, within the plane when contracted; and

A third SMA wire is arranged to apply a force to the movable part in a third direction in the plane when contracted so as to oppose the force applied by the first SAM wire and/or the second SAM wire.

3. An SMA actuator assembly according to claim 2, wherein the first and second directions are orthogonal directions.

4. A SMA actuator assembly according to claim 2 or 3, wherein the third SMA wire extends in a direction different from the third direction, and wherein the SMA actuator assembly further comprises an intermediate element configured to redirect tension in the third SMA wire along the third direction.

5. An SMA actuator assembly according to claim 4, wherein the intermediate element comprises a flexure arm connected at one end to the support structure and at the other end to the movable part, wherein the flexure arm is arranged such that the other end is allowed to move in the third direction relative to the support structure, and

wherein the third SMA wire is connected to the flexure arm and configured to deflect the flexure arm upon contraction, pushing the other end of the flexure arm in the third direction.

6. An SMA actuator assembly according to claim 4, wherein the intermediate element is arranged between the third SMA wire and the movable part, wherein the third SMA wire is bent around a contact area with the intermediate element, thereby forming two SMA portions on both sides of the contact area, the two SMA portions being angled with respect to each other.

7. An SMA actuator assembly according to claim 6, wherein the intermediate element allows movement of the movable part relative to the contact region within the plane.

8. An SMA actuator assembly according to claim 7, wherein the intermediate element comprises a flexure arm extending substantially in the third direction, one end of the flexure arm being connected to the movable part and the other end of the flexure arm being connected to the contact region.

9. An SMA actuator assembly according to claim 7, wherein the intermediate element comprises a rolling bearing comprising a rolling element between two bearing surfaces connected to the movable part and the contact area, respectively, the two bearing surfaces extending substantially perpendicular to the third direction.

10. An SMA actuator assembly according to any one of claims 6 to 9, wherein the intermediate element prevents rotation of the movable component relative to the contact region about any axis perpendicular to the plane, the intermediate element thereby comprising the anti-rotation mechanism.

11. An SMA actuator assembly according to claim 9, wherein the intermediate element comprises two rolling elements arranged such that rotation of the two bearing surfaces relative to each other about any axis perpendicular to the plane is prevented.

12. An SMA actuator assembly according to any preceding claim, wherein each SMA wire extends along an edge of the movable part or towards a centre of the movable part.

13. An SMA actuator assembly according to any preceding claim, wherein at least one SMA wire extends between the movable part and the support structure along an axis perpendicular to the plane.

14. An SMA actuator assembly according to claim 13, wherein the at least one SMA wire extends between two opposite corners of the movable part.

15. An SMA actuator assembly according to any preceding claim, further comprising a bearing arrangement configured to support the movable component on the support structure in a manner that allows movement of the movable component relative to the support structure in the plane.

16. An SMA actuator assembly according to claim 15, wherein the bearing arrangement is configured to limit rotation of the movable part relative to the support structure about any axis perpendicular to the plane, the bearing arrangement thereby comprising the anti-rotation mechanism.

17. An SMA actuator assembly according to claim 16, wherein the bearing arrangement comprises two pairs of flexure arms connected in mechanical series between the movable part and the support structure, wherein each pair of flexure arms allows movement in a respective one of two orthogonal directions in the plane.

18. An SMA actuator assembly according to claim 16, wherein the bearing arrangement comprises two rolling bearings arranged in mechanical series between the movable part and the support structure, wherein each rolling bearing allows movement in a respective one of two orthogonal directions in the plane.

19. An SMA actuator assembly according to any preceding claim, wherein the three SMA wires are arranged on the same half edge of the perimeter of the movable part.

20. A Shape Memory Alloy (SMA) actuator assembly comprising:

a support structure;

a movable member movable in a plane relative to the support structure;

an anti-rotation mechanism configured to limit rotation of the movable component relative to the support structure about any axis perpendicular to the plane;

a total of two SMA wires, wherein none of the SMA wires is collinear, and wherein the SMA wires are individually controllable to apply a force to the movable part in two directions in the plane; and

a biasing arrangement configured to apply a force to the movable component that is opposite to the force applied by the two SMA wires.

21. An SMA actuator assembly according to claim 20, wherein the two directions are two orthogonal directions.

22. An SMA actuator assembly according to claim 20 or 21, wherein each SMA wire extends along an edge of the movable part or towards a centre of the movable part.

23. An SMA actuator assembly according to any one of claims 20 to 22, wherein at least one SMA wire extends between the movable part and the support structure along an axis perpendicular to the plane.

24. An SMA actuator assembly according to claim 23, wherein the at least one SMA wire extends between two opposite corners of the movable part.

25. An SMA actuator assembly according to any one of claims 20 to 24, wherein the anti-rotation mechanism comprises the biasing arrangement.

26. An SMA actuator assembly according to any one of claims 20 to 25, further comprising a bearing arrangement configured to support the movable component on the support structure in a manner that allows movement of the movable component relative to the support structure in the plane.

27. An SMA actuator assembly according to claim 26, wherein the bearing arrangement is configured to limit rotation of the movable part relative to the support structure about any axis perpendicular to the plane, the bearing arrangement thereby comprising the anti-rotation mechanism.

28. A camera device comprising an SMA actuator assembly according to any preceding claim,

the camera device further comprises an image sensor fixed relative to the support structure; and is also provided with

Wherein the movable component comprises a lens assembly comprising one or more lenses configured to focus an image on the image sensor.

29. The camera device of claim 28, further comprising a vibration sensor configured to generate an output signal representative of vibration of the camera device; and

a control circuit arranged to generate a drive signal for the SMA wire in response to the output signal of the vibration sensor for driving movement of the movable part so as to stabilize the image sensed by the image sensor and to supply the generated drive signal to the SMA wire.