SHAPE MEMORY ALLOY ACTUATION APPARATUS

• US 20150135703A1
• Filed: 05/21/2013
• Published: 05/21/2015
• Est. Priority Date: 05/25/2012
• Status: Active Grant

• Current Assignee: Cambridge Mechatronics Limited
• Original Assignee: Cambridge Mechatronics Limited
• Inventors: Eddington, Robin, Howarth, James, Brown, Andrew Benjamin David
• Granted Patent: US 9,518,566 B2
• Time in Patent Office: Days
• US Class Current: 60/528
• CPC Class Codes: F03G 7/065 using a shape memory element
• CPC Class Codes: G02B 27/646 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 Class Codes: G03B 2205/0015 by displacing one or more optical elements normal to the optical axis
• CPC Class Codes: G03B 2205/0076 using shape memory alloys
• CPC Class Codes: G03B 5/00 Adjustment of optical system relative to image or object surface other than for focusing
• CPC Class Codes: H04N 23/687 by shifting the lens or sensor position

Abstract

An SMA actuation apparatus moves a movable element relative to a support structure in two orthogonal directions using a total of four SMA actuator wires each connected at its ends between the movable element and the support structure and extending perpendicular to the primary axis. None of the SMA actuator wires are collinear, but the SMA actuator wires have an arrangement in which they are capable of being selectively driven to move the movable element relative to the support structure to any position in said range of movement without applying any net torque to the movable element in the plane of the two orthogonal directions around the primary axis. Accordingly, it is possible to drive movement whilst balancing the forces to limit torque around the primary axis.

Claims

1. An SMA actuation apparatus for moving a movable element relative to a support structure in two orthogonal directions, the SMA actuation apparatus comprising:

a support structure;

a movable element supported on the support structure in a manner allowing movement of the movable element relative to the support structure across a range of movement in two orthogonal directions perpendicular to a notional primary axis extending through the movable element; and

a total of four SMA actuator wires connected between the movable element and the support structure in an arrangement wherein none of the SMA actuator wires are collinear, and wherein the SMA actuator wires are capable of being selectively driven to move the movable element relative to the support structure to any position in said range of movement without applying any net torque to the movable element in the plane of the two orthogonal directions around the primary axis.

2. The apparatus according to claim 1, wherein the SMA actuation apparatus is a camera apparatus further comprising an image sensor fixed to the support structure, and the movable element comprises a camera lens element comprising one or more lenses arranged to focus an image on the image sensor, the primary axis being the optical axis of the camera lens element.

3. The apparatus according to claim 2, wherein the at least one lens has a diameter of at most 10 mm.

4. The apparatus according to claim 3, wherein the camera lens element comprises a lens carrier on which the one or more lenses are supported in a manner in which at least one of the one or more lenses is movable along the optical axis.

5. The apparatus according to claim 2, further comprising:

a vibration sensor arranged to generate output signals representative of the vibration of the apparatus; and

a control circuit arranged to generate drive signals for the SMA actuator wires in response to the output signals of the vibration sensor for driving the movement of the camera lens element to stabilise the image sensed by the image sensor, and to supply the generated drive signals to the SMA actuator wires.

6. The apparatus according to claim 5, wherein the control circuit is arranged to generate drive signals for driving the movement of the camera lens element to stabilise the image sensed by the image sensor without applying any torque to the movable element in the plane of the two orthogonal directions around the primary axis.

7. The apparatus according to claim 1, further comprising a control circuit arranged to generate drive signals for the SMA actuator wires, and to supply the generated drive signals to the SMA actuator wires.

8. The apparatus according to claim 7, wherein the control circuit is arranged to generate drive signals for driving the movement of the camera lens element without applying any torque to the movable element in the plane of the two orthogonal directions around the primary axis.

9. The apparatus according to claim 7, wherein the control circuit is arranged to generate drive signals for driving the movement of the camera lens element whilst applying a predetermined amount of torque to the movable element in the plane of the two orthogonal directions around the primary axis.

10. The apparatus according to claim 9, further comprising a suspension system supporting the movable element on the support structure in said manner allowing movement of the movable element relative to the support structure in two orthogonal directions each perpendicular to the primary axis, wherein the suspension system applies a torque to the movable element in the plane of the two orthogonal directions around the primary axis and the predetermined amount of torque applied by the generated drive signals compensates for torque applied by the suspension system.

11. The apparatus according to claim 1, wherein two of the SMA actuator wires are connected between the movable element and the support structure to each apply a torque to the movable element in said plane around the primary axis in a first sense around the primary axis and the other two SMA actuator wires are connected between the movable element and the support structure to each apply a torque to the movable element in said plane around the primary axis in a second, opposite sense around the primary axis.

12. The apparatus according to claim 1, wherein the four SMA actuator wires are arranged in a loop at different angular positions around the primary axis, successive SMA actuator wires around the primary axis being connected to apply a force to the movable element in alternate senses around the primary axis.

13. The apparatus according to claim 1, wherein the four SMA actuator wires consist of two pairs of SMA actuator wires wherein the first pair of SMA actuator wires is arranged to be capable of being selectively driven to drive the movable element relative to the support structure in a first direction in said plane, and to generate a net torque to the movable element in said plane around the primary axis, and the second pair of SMA actuator wires is arranged to be capable of being selectively driven to drive the movable element relative to the support structure in a second direction in said plane transverse to the first direction, and to generate a net torque to the movable element in said plane around the primary axis that is in an opposite sense to the first pair of SMA wires.

14. The apparatus according to claim 13, wherein within each pair of SMA actuator wires, the two SMA actuator wires are arranged on opposite sides of the primary axis.

15. The apparatus according to claim 13, wherein within each pair of SMA actuator wires, the two SMA actuator wires are arranged on the same side of the primary axis at different distances from the primary axis.

16. The apparatus according to claim 1, wherein each of the SMA actuator wires extends perpendicular to the primary axis.

17. The apparatus according to claim 16, wherein the SMA actuator wires extend in a common plane.

18. The apparatus according to claim 1, further comprising a suspension system supporting the movable element on the support structure in said manner allowing movement of the movable element relative to the support structure in two orthogonal directions each perpendicular to the primary axis.

19. The apparatus according to claim 18, wherein the suspension system comprises a plurality of beams extending transverse to said two orthogonal directions.

20. The apparatus according to claim 19, wherein the beams extend parallel to the primary axis.

21. The apparatus according to claim 19, wherein the beams are formed by wires.