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WO-2026093730-A1 - ACTUATOR ASSEMBLY

WO2026093730A1WO 2026093730 A1WO2026093730 A1WO 2026093730A1WO-2026093730-A1

Abstract

An actuator assembly comprising a first part; a rotatable part arranged to be rotatable relative to the first part; a shape memory alloy, SMA, element connected between first and second connection parts, wherein the first connection part is coupled to the first part and the second connection part is coupled to the rotatable part so that the SMA element is configured, on actuation, to apply an input force to the rotatable part, thereby causing the rotatable part to rotate relative to the first part; and a connector coupling configured to couple the second connection part to the rotatable part and to transmit the input force from the SMA element to the rotatable part and to allow rotation of the second connection part relative to the rotatable part.

Inventors

  • BROWN, ANDREW BENJAMIN SIMPSON
  • BUNTING, Stephen Matthew
  • HEIJNE, Nicholas

Assignees

  • CAMBRIDGE MECHATRONICS LIMITED

Dates

Publication Date
20260507
Application Date
20251027
Priority Date
20241028

Claims (20)

  1. 1. An actuator assembly comprising a first part; a rotatable part arranged to be rotatable relative to the first part; a shape memory alloy, SMA, element connected between first and second connection parts, wherein the first connection part is coupled to the first part and the second connection part is coupled to the rotatable part so that the SMA element is configured, on actuation, to apply an input force to the rotatable part, thereby causing the rotatable part to rotate relative to the first part; and a connector coupling configured to couple the second connection part to the rotatable part and to transmit the input force from the SMA element to the rotatable part and to allow rotation of the second connection part relative to the rotatable part.
  2. 2. An actuator assembly according to claim 1, wherein the connector coupling is configured such that the second connection part, on actuation of the SMA element, moves translationally relative to the first part.
  3. 3. An actuator assembly according to claim 1 or 2, further comprising a bearing arrangement configured to guide translational movement of the second connection part relative to the first part.
  4. 4. An actuator assembly according to claim 3, wherein the bearing arrangement comprises a plain bearing or a rolling bearing arranged to guide translational movement of the second connection part relative to the first part.
  5. 5. An actuator assembly according to claim 3 or 4, wherein the second connection part comprises a main portion and a connector portion fixedly connected to the main portion, wherein the SMA element is held by the connector portion and wherein the bearing arrangement is arranged between the main portion and the first part, and wherein the main portion is elongate between first and second ends, and wherein the connector portion is arranged on the first end of the main portion and the bearing arrangement is arranged on the second end of the main portion.
  6. 6. An actuator assembly according to any one of claims 3 to 5, wherein the three lines comprising i) an imaginary line along a force exerted by the SMA element on the second connection part, ii) an imaginary line along a force exerted by the connector coupling on the second connection part and iii) an imaginary line along a force exerted by the bearing arrangement on the second connection part intersect at a common point.
  7. 7. An actuator assembly according to any one of the preceding claims, wherein the connector coupling comprises a rotation bearing arranged between the rotatable part and the second connection part, the rotation bearing allowing the rotation of the second connection part relative to the rotatable part about a pivot axis.
  8. 8. An actuator assembly according to claim 7, wherein the rotation bearing is a plain bearing or a rolling bearing.
  9. 9. An actuator assembly according to claim 7 or 8, wherein the pivot axis lies on an imaginary line along a force applied by the SMA element to the second connection part.
  10. 10. An actuator assembly according to any one of claims 7 to 9, wherein the pivot axis lies beyond an end the SMA element extending from the second connection part when viewed from the first connection part.
  11. 11. An actuator assembly according to any one of claims 7 to 10, wherein the distance between the pivot axis and an end the SMA element extending from the second connection part is within a range from 1% to 10% of a length of the SMA element.
  12. 12. An actuator assembly according to any one of the preceding claims, wherein the connector coupling comprises a coupling flexure allowing the rotation of the second connection part relative to the rotatable part.
  13. 13. An actuator assembly according to claim 12, wherein a length of the coupling flexure is collinear with or at an acute angle to a force applied by the SMA element to the second connection part.
  14. 14. An actuator assembly according to claim 12 or 13, wherein the coupling flexure is placed under tension on actuation of the SMA element.
  15. 15. An actuator assembly according to any one of claims 12 to 14, wherein the coupling flexure overlaps with the SMA element when viewed perpendicularly to a length of the coupling flexure.
  16. 16. An actuator assembly according to any one of claims 12 to 15, wherein the coupling flexure is formed integrally with the rotatable part and/or with the second connection part.
  17. 17. An actuator assembly according to any one of the preceding claims, wherein the first and second connection parts respectively comprise first and second crimps.
  18. 18. An actuator assembly according to any one of the preceding claims, wherein the rotatable part is rotatable relative to the first part within a range of movement, and wherein the actuator assembly is configured to constrain rotation of the rotatable part relative to the first part at any position within the range of movement when the SMA element is not actuated.
  19. 19. An actuator assembly according to claim 18, comprising first and second friction surfaces that are biased against each other with a normal force, thereby generating a static frictional force between the first and second friction surfaces that constrains rotation of the rotatable part at any position within the range of movement when the SMA element is not actuated.
  20. 20. An actuator assembly according to claim 19, wherein the SMA element is configured, on actuation, to reduce the normal force between the first and second friction surfaces, thereby reducing the static frictional force therebetween.

Description

ACTUATOR ASSEMBLY Field The present application relates to an actuator assembly, in particular a shape memory alloy (SMA) actuator assembly including an SMA element. Background SMA actuator assemblies may be used in a variety of applications for moving a movable part relative to a support structure. For example, WO 2013/175197 Al describes a camera in which four SMA wires are arranged to move a lens element relative to an image sensor in a plane that is perpendicular to the optical axis of the lens element, thereby effecting optical image stabilization (OIS). WO 2010/029316 Al describes SMA wires used to provide OIS in a camera by tilting a camera module. WO 2011/104518 Al describes an actuator assembly having eight SMA wires capable of effecting positional control of a movable element with multiple degrees of freedom. Typically, the range of movement (also known as "stroke") of such SMA actuator assemblies is limited by the maximum contraction of the SMA wires, and the actuating force is limited by the maximum force that can be generated by the SMA wires. To increase the movement range or the actuating force, longer or thicker SMA wires can be used, but this may be at the expense of increased cost, size and/or power, which may not be practical in miniature applications. WO 2022/084699 Al discloses an actuator assembly comprising at least one actuating unit (incorporating an SMA wire) that, on actuation, moves a movable part relative to a support structure. The actuating unit may be configured to increase the stroke or the actuating force and/or to re-direct the force applied by the SMA wire. Summary According to the present invention, there is provided an actuator assembly comprising a first part; a rotatable part arranged to be rotatable relative to the first part; a shape memory alloy, SMA, element connected between first and second connection parts, wherein the first connection part is coupled to the first part and the second connection part is coupled to the rotatable part so that the SMA element is configured, on actuation, to apply an input force to the rotatable part, thereby causing the rotatable part to rotate relative to the first part; and a connector coupling configured to couple the second connection part to the rotatable part and to transmit the input force from the SMA element to the rotatable part and to allow rotation of the second connection part relative to the rotatable part. The amount of rotation of the second connection part relative to the rotatable part, for a given amount of actuation of the SMA element (e.g. for a given amount of contraction of an SMA wire), is increased compared to an actuator assembly in which the connector coupling is omitted. The amount of rotation of the SMA element relative to the second connection part, for a given amount of actuation of the SMA element, is reduced compared to an actuator assembly in which the connector coupling is omitted. On actuation of the SMA element, the rotatable part may rotate in a first sense relative to the first part and the second connection part may rotate in a second sense, opposite to the first sense, relative to the rotatable part. The rotatable part need not undergo pure rotation and may undergo simultaneous rotational and translational movement. The rotatable part may also be referred to as an intermediate part or a body portion. The first connection part may be coupled to the first part by being fixedly connected to the first part. In some embodiments, the connector coupling is configured such that the second connection part, on actuation of the SMA element, moves translationally relative to the first part. The second connection part may move translationally in a direction along or at an acute angle to the input force. Some embodiments further comprise a bearing arrangement configured to guide translational movement of the second connection part relative to the first part. In some embodiments, the bearing arrangement comprises a plain bearing or a rolling bearing arranged to guide translational movement of the second connection part relative to the first part. In some embodiments, the second connection part comprises a main portion and a connector portion fixedly connected to the main portion, wherein the SMA element is held by the connector portion and wherein the bearing arrangement is arranged between the main portion and the first part, and wherein the main portion is elongate between first and second ends, and wherein the connector portion is arranged on the first end of the main portion and the bearing arrangement is arranged on the second end of the main portion. In some embodiments, the three lines comprising i) an imaginary line along a force exerted by the SMA element on the second connection part, ii) an imaginary line along a force exerted by the connector coupling on the second connection part and iii) an imaginary line along a force exerted by the bearing arrangement on the second connection part inter