WO2023057765A1

WO2023057765A1 - An actuator assembly

Info

Publication number: WO2023057765A1
Application number: PCT/GB2022/052533
Authority: WO
Inventors: Samuel ARMSTRONG
Original assignee: Cambridge Mechatronics Limited
Priority date: 2021-10-06
Filing date: 2022-10-06
Publication date: 2023-04-13
Also published as: GB202404279D0; GB2625030A

Abstract

The application relates to an actuator assembly comprising: a support structure; a movable part; a drive arrangement configured to move the movable part relative to the support structure. The movable part comprises one or more end-stops protruding from corners and/or sides of the movable part, and configured to engage one or more complementary end-stops of the support structure so as to limit lateral movement of the movable part relative to the support structure in directions perpendicular to a primary axis. The one or more end-stops and the one or more complementary end-stops are configured such that a minimum lateral clearance between the one or more end-stops and the one or more complementary end-stops is maintained when the movable part is rotated about the primary axis.

Description

AN ACTUATOR ASSEMBLY

Field

The present invention relates to an actuator assembly with endstops.

Summary

According to an aspect of the present invention, there is provided an actuator assembly comprising: a support structure; a movable part; a drive arrangement configured to move the movable part relative to the support structure. The movable part comprises one or more (e.g. two) end-stops (which may also be referred to as end-stop components) protruding from corners and/or sides of the movable part, and configured to engage (e.g. abut) one or more (e.g. two) complementary end-stops of the support structure so as to limit lateral movement of the movable part relative to the support structure in directions perpendicular to a primary axis that is defined with reference to the support structure (and that e.g. passes through the movable part); and wherein (e.g. when viewed along the primary axis) the one or more end-stops and the one or more complementary end-stops are configured such that a minimum lateral clearance between the one or more end-stops and the one or more complementary end-stops is maintained when the movable part is rotated about the primary axis (e.g. by the drive arrangement).

The end-stops may be referred to as end-stop corners and/or end-stop protrusions.

Optionally, the one or more complementary end-stops and the one or more end-stops (e.g. end-stop corners) are configured to prevent the minimum lateral clearance between the one or more complementary endstops and the one or more end-stops (e.g. endstop corners) from decreasing when the movable part is rotated about the primary axis (e.g. by the drive arrangement).

Optionally, when viewed along the primary axis, each end-stop (e.g. end-stop corner) comprises an obtuse-angled (end-stop) corner (configured to engage the complementary end-stops).

Optionally, each of the one or more end-stops comprises a first and a second end-stop surface; wherein the angle between the first and second end-stop surfaces of each end-stops is greater than 90° (e.g. when viewed along the primary axis).

Optionally, each of the one or more complementary end-stops comprises a first and a second endstop surface; wherein the first and second endstop surfaces of each complementary end-stop are perpendicular to each other; and wherein the one or more end-stops (e.g. the first and second endstop surfaces of the end-stop) are configured to engage (e.g. abut) the first and second end-stop surfaces of the complementary end-stops. Optionally, the one or more end-stops comprise (e.g. a total of) two end-stops provided on opposite corners of the movable part.

Optionally, the end-stops (e.g. endstop corners) are provided on opposite sides of the movable part.

Optionally, the movable part comprises coupling components (e.g. crimp corners), and the coupling components are provided on opposite corners (e.g. sides) of the movable part. The coupling components may be referred to as SMA element coupling components as they may be for coupling SMA elements to the movable part.

Optionally, the two end-stops (e.g. the corners of the movable part comprising the end-stops) and the coupling components (e.g. the corners of the movable part comprising the coupling components) are (e.g. equi-)angularly spaced (apart) from each other (e.g. by 90 degrees) around the primary axis.

Optionally, the endstops are shaped (e.g. rounded or spherically shaped) such that the minimum (lateral) clearance between the end-stops and the complementary end-stops is maintained when the movable part is rotated about a tilt axis (e.g. by the drive arrangement); wherein the tilt axis is an axis perpendicular to the primary axis.

Optionally, when viewed along an axis perpendicular to the primary axis, the movable part comprises obtuse-angled corners.

Optionally, the movable part comprises an electronic component.

Optionally, the electronic component defines a plane, and the primary axis is perpendicular to the plane.

Optionally, the electronic component comprises an image sensor comprising a light-sensitive region (e.g. light-sensitive area), and wherein the primary axis is perpendicular to the light-sensitive region.

Optionally, the electronic component comprises a display or an emitter, and wherein the primary axis is parallel to a general direction in which the display or emitter emits light.

Optionally, the movable part comprises a lens assembly.

Optionally, the movable part comprises a second drive arrangement configured to move the lens assembly along the optical axis of the lens assembly.

Optionally, the primary axis is, or corresponds to, the optical axis of the lens assembly. Optionally, the drive arrangement comprises one or more shape memory alloy (SMA) elements arranged, on actuation (e.g. contraction), to drive movement of the movable part relative to the support structure.

Optionally, the one or more SMA elements are operatively connected between the support structure and the movable part (e.g. via the coupling components).

Optionally, the actuator assembly comprises eight SMA elements divided in two groups of four SMA elements, and wherein: two SMA elements are located on each of four sides around the primary axis, the four sides extending in a loop around the primary axis; the two SMA elements on each of the four sides are inclined with respect to the primary axis; the SMA elements of each of the two groups of four SMA elements are arranged with a 2-fold rotational symmetry about the primary axis; and one of the two groups of four SMA elements provides a force on the movable part with a component in a first direction along the primary axis and the other of the two groups of four SMA elements provides a force on the movable part with a component in a second direction along the primary axis, opposite to the first direction along the primary axis. The SMA elements may be or may comprise SMA wires.

Brief Description of the Drawings

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

Figure 1 is an exploded view of a first SMA actuator assembly;

Figures 2 and 3 are schematic plan views of the first SMA actuator assembly;

Figures 4 and 5 are schematic side views of the first SMA actuator assembly; Figures 6 and 7 are schematic plan views of a second SMA actuator assembly; Figure 8 is a schematic side view of the second SMA actuator assembly; and Figures 9 and 10 are schematic plan views of a third SMA actuator assembly.

Detailed Description

Figures 1-5 show a first actuator assembly 10 (herein also referred to as the SMA actuator arrangement 10) of the type described in W02011/104518 ('P284').

The first SMA actuator arrangement 10 includes a static part 5 (herein also referred to as a support structure 5) that comprises a base 11 that, in this example, is an integrated chassis and sensor bracket for mounting an image sensor, and a screening can 12 attached to the base 11. The SMA actuator arrangement 10 includes a moving part 6 (herein also referred to as a movable part 6) that, in this example, is a camera lens assembly comprising a lens carriage 13 carrying at least one lens (not shown).

The SMA actuator arrangement 10 includes a drive arrangement comprising eight SMA wires 2 each attached between the static part 5 and the moving part 6, and configured to move the movable part 6 relative to the support structure 5 upon selective contraction of the SMA wires 2. A pair of SMA wires 2 that cross each other are provided on each of four sides of the SMA actuator arrangement 10 as viewed along a primary axis P defined with reference to the support structure 5. The SMA wires 2 have an overall configuration of the type illustrated in Fig. 4 of WO-2011/104518. As described in WO-2011/104518, which is incorporated herein by reference and to which reference is made, the SMA wires 2 are attached to the static part 5 and the moving part 6 in such a configuration that they are capable of providing relative movement of the moving part 5 with multiple degrees of freedom for providing both autofocus (AF) and optical image stabilisation (OIS). Thus, in respect of each pair of SMA wires 2, the SMA wires 2 are attached at one end to two static mount portions 15 which are themselves mounted to the static part 5 for attaching the SMA wires 2 to the static part 5. The static mount portions 15 are adjacent one another but are separated to allow them to be at different electrical potentials. Similarly, in respect of each pair of SMA wires 2, the SMA wires 2 are attached at one end to a moving mount portion 16 which is itself mounted to the moving part 6 for attaching the SMA wires 2 to the moving part 6. The moving part 6 further comprises a conductive ring 17 connected to each of the moving mount portions 16 for electrically connecting the SMA wires 2 together at the moving part 6.

The movable part 6 comprises two end-stops 130 protruding from corners and/or sides of the movable part 6. As viewed along the primary axis P, and as shown in Figures 2 and 3, each end-stop 130 of the movable part 6 comprises a right-angled corner. The endstops 130 are provided on opposite corners/sides of the movable part 6 (as viewed along the primary axis P).

The movable part 6 comprises a first group of coupling components (e.g. crimps) for coupling the SMA wires 2 to the support structure 5, and a second group of coupling components (e.g. crimps) for coupling the SMA wires 2 to the movable part 6. The first group of coupling components are provided on opposite corners/sides of the movable part 6. The endstops 130 (or the corners of the movable part 6 comprising the endstops 130) and the first group of coupling components (or the corners of the movable part 6 comprising the first group of coupling components) are angularly (or e.g. equi-angularly) spaced apart from each other around the primary axis P.

The support structure 5 comprises two complementary end-stops 110. Each complementary endstop 110 comprises a first and a second endstop surface. As shown in, Figures 2 and 3, the first and second endstop surfaces of the complementary endstops 110 are perpendicular to each other. The endstops 130 and complementary endstops 110 are configured to engage so as to limit lateral movement of the movable part 6 relative to the support structure 5 in directions perpendicular to the primary axis P.

As shown in Figure 3, in this assembly, the (minimum) lateral clearance C between the endstop corners 130 and the endstop surfaces of the complementary endstops 110 decreases when the movable part 6 is rotated about the primary axis P.

Moreover, as shown in Figure 5, in this assembly, the lateral clearance C between the endstop corners 130 and the endstop surfaces also decreases when the movable part 6 is rotated about a tilt axis R, wherein the tilt axis R is an axis perpendicular to the primary axis P. Figures 6-8 show a second actuator assembly. The second actuator assembly comprises the same features that the first actuator assembly 10 comprises. However, it differs in that, when viewed along the primary axis P, each end-stop 130' of the movable part 6' comprises an obtuse-angled (endstop) corner, instead of a right-angled corner. In other words, it differs in that the first and second endstop surfaces of the endstop 130' are configured such that the angle between the first and second endstop surfaces of the endstops 130' is greater than 90° (when viewed along the primary axis P).

As shown in Figure 7, this arrangement prevents the (minimum) lateral clearance C between the endstops 130' and the endstop surfaces of the complementary end-stops 110' from decreasing when/as the movable part 6' is rotated about the primary axis P (up by a certain degree). In other words, the endstops 130' and the complementary endstops 110' are configured such that a minimum lateral clearance between the endstops 130' and the complementary endstops 110' is maintained when the movable part 6' is rotated about the primary axis P (e.g. by the drive arrangement).

This arrangement ensures that the minimum lateral clearance C between the endstops 130' and the endstop surfaces of the complementary endstops 110' is kept constant when/as the movable part 6' is rotated about the primary axis P (up to a certain angle).

The skilled person would understand that the above could also be achieved by instead providing the endstop surfaces of the complementary endstops 110' with an obtuse angle and having the endstop corners as right-angled corners (as viewed along the primary axis P). In other words, having the first and second endstop surfaces of the complementary endstops 110' configured such that the angle between the first and second endstop surfaces of the complementary endstops 110' is greater than 90° (when viewed along the primary axis P).

As shown in Figure 8, the endstops 130' may be shaped so that the (minimum) lateral clearance C between the endstops 130' and the endstop surfaces of the complementary endstops 110' does not decrease (e.g. is maintained) when/as the movable part 6' is rotated about a tilt axis R by the drive arrangement (optionally, up to a certain angle). The tilt axis R may be any axis perpendicular to the primary axis P. Moreover, as viewed along an axis perpendicular to the primary axis P (and as shown in Figure 8), the movable part 6' may comprise obtuse-angled corners that prevent the vertical clearance Z between the movable part 6' and the support structure 5' to be less than a predetermined amount Z1 when/as the movable part 6' is rotated around the tilt axis R (up to a certain angle).

Figures 9 and 10 show a third actuator assembly. The third actuator assembly comprises the same features that the second actuator assembly comprises, except that the movable part 6" is shaped differently.

Other variations

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

For example, the image sensor may be provided on the movable part of the above-described actuator assemblies, rather than on the support structure.

Where the movable part comprises a lens assembly, the movable part may comprise a second drive arrangement configured to move the lens assembly along the optical axis of the lens assembly. The optical axis of the lens assembly may correspond or be parallel to the primary axis P (e.g. when the movable part has not been tilted about a tilt axis).

For example, the actuator assemblies described above may be used to move any electronic component with respect to a support structure (instead of e.g. a camera lens assembly), such as a display, an emitter, or a part thereof.

Where the movable part comprises an emitter or a display (or a part thereof), the movable part may be moved to achieve wobulation, for example for the display of a super-resolution image (i.e. an image having a resolution higher than that of the intrinsic resolution of the emitter or display). In this case, a high-resolution image is displayed (or projected) by displaying a number of lower- resolution images at different positions in rapid succession. The image displayed at each position is a lower-resolution image formed of a subset of pixels of the high-resolution image. The movable part may be moved between the positions in a repeated pattern at a high frequency, for example greater than 30 Hz, preferably greater than 60 Hz, further preferably greater than 120 Hz. The succession of lower-resolution images is thus perceived by the human eye as one high-resolution image. The display may be a display panel, for example a LCOS (liquid crystal on silicon) display, a MicroLED display, a digital micromirror device (DMD) or a laser beam scanning (LBS) system.

In the case the movable part comprises an emitter, the emitter may be configured to emit radiation (visible light or non-visible radiation, e.g. near infrared (NIR) light, short-wave infrared (SWIR) light). The emitter may comprise one or more LEDs or lasers, for example VCSELs (vertical-cavity surfaceemitting lasers) or edge-emitting lasers. The emitter may comprise a VCSEL array. The emitter may otherwise be referred to as an illumination source and/or may comprise an image projector.

In the case that the movable part comprises a display, the display may define a plane and the primary axis may be perpendicular to the plane defined by the display. In any case, the primary axis may be aligned with a general direction in which light is emitted from the display. In the case that the movable part comprises an emitter, the emitter may define a plane and the primary axis may be perpendicular to the plane defined by the emitter. For example, the emitter may comprise a VCSEL array and the primary axis may be perpendicular to the plane of the VCSEL array. In any case, the primary axis may be aligned with a general direction in which radiation is emitted by the emitter.

SMA

The actuator assemblies described herein comprise at least one SMA wire. The SMA wire may instead be an SMA element. The term 'shape memory alloy (SMA) element' may refer to any element comprising SMA. The SMA element may be described as an SMA wire. The SMA element may have any shape that is suitable for the purposes described herein. The SMA element may be elongate and may have a round cross section or any other shape cross section. The cross section may vary along the length of the SMA element. The SMA element might have a relatively complex shape such as a helical spring. It is also possible that the length of the SMA element (however defined) may be similar to one or more of its other dimensions. The SMA element may be sheet-like, and such a sheet may be planar or non-planar. The SMA element may be pliant or, in other words, flexible. In some examples, when connected in a straight line between two components, the SMA element can apply only a tensile force which urges the two components together. In other examples, the SMA element may be bent around a component and can apply a force to the component as the SMA element tends to straighten under tension. The SMA element may be beam-like or rigid and may be able to apply different (e.g. non-tensile) forces to elements. The SMA element may or may not include material(s) and/or component(s) that are not SMA. For example, the SMA element may comprise a core of SMA and a coating of non-SMA material. Unless the context requires otherwise, the term 'SMA element' may refer to any configuration of SMA material acting as a single actuating element which, for example, can be individually controlled to produce a force on an element. For example, the SMA element may comprise two or more portions of SMA material that are arranged mechanically in parallel and/or in series. In some arrangements, the SMA element may be part of a larger SMA element. Such a larger SMA element might comprise two or more parts that are individually controllable, thereby forming two or more SMA elements. The SMA element may comprise an SMA wire, SMA foil, SMA film or any other configuration of SMA material. The SMA element may be manufactured using any suitable method, for example by a method involving drawing, rolling, deposition, sintering or powder fusion. The SMA element may exhibit any shape memory effect, e.g. a thermal shape memory effect or a magnetic shape memory effect, and may be controlled in any suitable way, e.g. by Joule heating, another heating technique or by applying a magnetic field.

Claims

1. An actuator assembly comprising: a support structure; a movable part; a drive arrangement configured to move the movable part relative to the support structure; wherein the movable part comprises one or more end-stops protruding from corners and/or sides of the movable part, and configured to engage one or more complementary end-stops of the support structure so as to limit lateral movement of the movable part relative to the support structure in directions perpendicular to a primary axis that is defined with reference to the support structure; and wherein the one or more end-stops and the one or more complementary end-stops are configured such that the minimum lateral clearance between the one or more end-stops and the one or more complementary end-stops is maintained when the movable part is rotated about the primary axis.

2. An actuator assembly according to claim 1, wherein the one or more end-stops and the one or more complementary end-stops are configured to prevent the minimum lateral clearance between the one or more end-stops and the one or more complementary end-stops from decreasing when the movable part is rotated about the primary axis.

3. An actuator assembly according to claim 1 or 2, wherein, when viewed along the primary axis, each of the one or more end-stops comprise an obtuse-angled end-stop corner.

4. An actuator assembly according to any preceding claim, wherein each of the one or more end-stops comprise a first and a second end-stop surface; wherein the angle between the first and second end-stop surfaces of each end-stop is greater than 90°.

5. An actuator assembly according to any preceding claim, wherein each of the one or more complementary end-stops comprises a first and a second end-stop surface; wherein the first and second end-stop surfaces of each complementary end-stop are perpendicular to each other; and wherein the one or more end-stops are configured to engage the first and second end-stop surfaces of the complementary end-stops.

6. An actuator assembly according to any preceding claim, wherein the one or more end-stops comprise two end-stops provided on opposite corners of the movable part.

7. An actuator assembly according to any preceding claim, wherein the movable part comprises shape memory alloy (SMA) element coupling components provided on opposite corners of the movable part.

8. An actuator assembly according to claim 7 when dependent on claim 6, wherein the two end-stops and the coupling components are angularly spaced apart from each other around the primary axis.

9. An actuator assembly according to any preceding claim, wherein the end-stops are shaped such that the minimum lateral clearance between the end-stops and the complementary end-stops is maintained when the movable part is rotated about a tilt axis; wherein the tilt axis is an axis perpendicular to the primary axis.

10. An actuator assembly according to any preceding claim, wherein, when viewed along an axis perpendicular to the primary axis, the movable part comprises obtuse-angled corners.

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

12. An actuator assembly according to claim 11, wherein the electronic component defines a plane, and the primary axis is perpendicular to the plane.

13. An actuator assembly according to claim 11 or 12, wherein the electronic component comprises an image sensor comprising a light-sensitive region, and wherein the primary axis is perpendicular to the light-sensitive region.

14. An actuator assembly according to claim 11 or 12, wherein the electronic component comprises a display or an emitter, and wherein the primary axis is parallel to a general direction in which the display or emitter emits light.

15. An actuator assembly according to any of claims 1 to 13, wherein the movable part comprises a lens assembly.

16. An actuator assembly according to claim 15, wherein the movable part comprises a second drive arrangement configured to move the lens assembly along the optical axis of the lens assembly.

17. An actuator assembly according to claim 15 or 16, wherein the primary axis corresponds to the optical axis of the lens assembly.

18. An actuator assembly according to any preceding claim, wherein the drive arrangement comprises one or more shape memory alloy (SMA) elements arranged, on actuation, to drive movement of the movable part relative to the support structure.

19. An actuator assembly according to claim 18, wherein the one or more SMA elements are operatively connected between the support structure and the movable part.

20. An actuator assembly according to claim 18 or 19, wherein the actuator assembly comprises eight SMA elements divided in two groups of four SMA elements, and wherein: two SMA elements are located on each of four sides around the primary axis, the four sides extending in a loop around the primary axis; the two SMA elements on each of the four sides are inclined with respect to the primary axis; the SMA elements of each of the two groups of four SMA elements are arranged with a 2-fold rotational symmetry about the primary axis; and one of the two groups of four SMA elements provides a force on the movable part with a component in a first direction along the primary axis and the other of the two groups of four SMA elements provides a force on the movable part with a component in a second direction along the primary axis, opposite to the first direction along the primary axis.

21. An actuator assembly according to any of claims 18 to 20, wherein the SMA elements comprise or are SMA wires.