Shape memory alloy actuator assembly

Patent metadata

Field	Value
Publication number	US-12585137-B2
Application number	US-202017611642-A
Country	US
Kind code	B2
Filing date	May 18, 2020
Priority date	May 17, 2019
Publication date	Mar 24, 2026
Grant date	Mar 24, 2026

Abstract

An actuator assembly ( 140 ) comprises first and second parts. A first axis (Z) is defined with reference to the second part. The actuator assembly ( 140 ) comprises shape-memory alloy wire ( 80 ) connected between the first and second parts for moving the first part relative to the second part in any of a set of directions that are at least partly perpendicular to the first axis (Z). The set of directions includes first and second directions. The actuator assembly ( 140 ) comprises a set of arms ( 170 ), each of which is connected between the first and second parts and extends partly around the first axis (Z). The set of arms ( 170 ) is configured to provide a biasing force that biases the first part towards a first position relative to the second part. The set of arms ( 170 ) has a first stiffness when the first part is moved away from the first position in the first direction and a second, lower stiffness when the first part is moved away from the first position in the second direction. At least one of the set of arms ( 170 ) comprises a portion ( 100 ) that is configured to decrease the first stiffness by a larger relative amount than the portion ( 100 ) decreases the second stiffness.

First claim

The invention claimed is:

1 . An actuator assembly comprising:
a first part and a second part, wherein a first axis is defined with reference to the second part; a shape memory alloy (SMA) wire connected to the first and second parts, the SMA wire for moving the first part relative to the second part in any of a set of directions that are at least partly perpendicular to the first axis, wherein the set of directions includes first and second directions; a set of arms, each of which is connected to the first and second parts and extends partly around the first axis, the set of arms configured to provide a biasing force that biases the first part towards a first position relative to the second part; wherein the set of arms has a first stiffness when the first part is moved away from the first position in the first direction and a second, lower stiffness when the first part is moved away from the first position in the second direction; wherein at least one of the set of arms comprises a portion that is configured to decrease the first stiffness by a larger amount relative to the amount that the portion decreases the second lower stiffness; and wherein the portion extends in a direction that is at least partly perpendicular to the first direction and at least partly parallel to the second direction, wherein the portion corresponds to at least one hairpin-shaped portion of the set of arms, wherein the hairpin-shaped portion comprises at least one pair of arm segments that extend alongside and generally parallel to each other and are connected to each other at one of the ends of the at least one pair of arm segments by a 180 degree turn.

2 . The actuator assembly according to claim 1 , wherein the portion comprises at least one pair of arm segments that generally extend parallel, or at an acute angle, to each other and are connected to each other at one of the ends of the at least one pair of arm segments; and:
wherein the at least one pair of arms segments extend alongside each other; and/or wherein each of the at least one pair of arm segments comprises at least one hairpin-shaped portion; and/or wherein a separation between the at least one pair of arm segments is increased in a region near the one of the ends.

3 . The actuator assembly according to claim 1 , wherein the portion comprises a length of arm that meanders within an envelope that extends away from or towards the first axis; and/or
comprising a damping substance connecting the portion to the second part or to another part of the actuator assembly that is fixed relative to the second part.

4 . The actuator assembly according to claim 1 , wherein each arm is limited to the inside or outside of a space around the first axis, wherein the boundary of the space has at least one recess into which the portion extends; and:
wherein the boundary is at least partly defined by a footprint of the actuator assembly and/or one or more features of the actuator assembly; and/or wherein the recess corresponds to a gap between two connectors each of which connects a length of SMA wire to the first part or the second part, and: the actuator assembly comprises four lengths of SMA wire, each of which is connected to a first connector on the first part and a second connector on the second part, wherein the first connectors are grouped in pairs and the second connectors are grouped in pairs, with the four pairs being substantially equally angularly spaced around the first axis and alternating between pairs of first connectors and pairs of second connectors, and wherein the boundary has two recesses each of which corresponds to a gap between a pair of first connectors or a pair of second connectors.

5 . The actuator assembly according to claim 1 , comprising two arms having substantially two-fold rotational symmetry about the first axis.

6 . The actuator assembly according to claim 1 , wherein the first direction is parallel with a first plane through the first axis, the second direction is parallel with a second plane through the first axis, and wherein the first and second planes are substantially perpendicular to each other; and:
wherein the portion is elongated in a direction that is substantially parallel to the second plane.

7 . The actuator assembly according to claim 1 , wherein the ratio of the first stiffness to the second, lower stiffness is less than 3:1.

8 . The actuator assembly according to claim 1 , wherein the at least one hairpin-shaped portion of the set of arms comprises a kinked arm.

Assignees

• Cambridge Mechatronics Ltd

Inventors

• Eddington Robin
• Auchoybur Kiran
• Polenta Valerio
• Pantelidis Konstantinos
• Kim Kang Jae Hee

Classifications

• F03G7/0665

  controlled displacement, e.g. by using a lens positioning actuator · CPC title

• F03G7/0636

  with several elements connected in parallel · CPC title

• H04N23/685

  performed by mechanical compensation · CPC title

• G03B2205/0076

  using shape memory alloys · CPC title

• G02B27/646 Primary

  compensating for small deviations, e.g. due to vibration or shake (movement of one or more optical elements for control of motion blur in cameras, projectors or printers G03B2205/0007; image stabilisation in cameras peculiar to the presence or use of an electronic image sensor H04N23/68) · CPC title