SHAPE MEMORY ALLOY ACTUATORS WITH SENSIBLE COATINGS

• US 20130227943A1
• Filed: 03/05/2012
• Published: 09/05/2013
• Est. Priority Date: 03/05/2012
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations LLC (General Motors Company)
• Inventors: Mance, Andrew M., Sulic, Martin P.
• Granted Patent: US 8,966,893 B2
• Time in Patent Office: Days
• US Class Current: 60/528
• CPC Class Codes: F03G 7/065 using a shape memory element

Abstract

Methods of applying sensible coatings with at least one spatially-varying characteristic to shape memory alloy actuators, particularly actuators comprising linear elements such as wires strips or cables, are disclosed. Such coatings enable the positions of the linear shape memory alloy elements to be sensed using magnetic, capacitive and optical sensors and so, in conjunction with a controller, enable operation of such actuators under proportional control.

Claims

1. A method of modifying an actuator comprising a linear shape memory alloy element for detection of movement of the actuator in an article of manufacture in which it is to be employed, the method comprising:

forming a sensible coating on a selected surface region of the linear shape memory alloy element, the coating being of a composition that is formed on the surface so as to provide a detectable signal reflective of movement of the actuator in the article of manufacture.

2. The method of claim 1 in which the sensible coating is formed in a pattern of coating segments for providing a sequenced of signals reflective of the movement of the actuator in the article of manufacture.

3. The method of claim 1 in which the sensible coating is of variable thickness for providing a signal of varying intensity reflective of the movement of the actuator in the article of manufacture.

4. The method of claim 1 in which the sensible coating is of variable composition for providing a signal of varying intensity reflective of the movement of the actuator in the article of manufacture.

5. The method of claim 1 in which the coating is metallic and deposited from aqueous solution.

6. The method of claim 5 in which the metallic coating is ferromagnetic.

7. The method of claim 1 in which the coating is metallic and deposited by thermal decomposition of a metal salt.

8. A method of controlling the position of a device in an article of manufacture comprising a sensor, the device being operatively connected to an actuator comprising shape memory alloy wire modified with a sensible coating of a composition that is formed on at least a portion of the wire surface so as to provide a detectable signal compatible with the sensor and reflective of movement of the device, the method comprising:

changing the shape memory alloy wire temperature and sensing the movement of the shape memory alloy wire;

relating the sensed motion of the wire to the device position; and

adjusting the shape memory alloy wire temperature to achieve a preferred device position.

9. The method of claim 8 in which the sensible coating is formed in a pattern of coating segments for providing a sequenced pattern of signals reflective of the movement of the shape memory wire actuator in the article of manufacture.

10. The method of claim 9 in which the pattern of coating segments varies along the length of the wire in a recognizable manner so that the wire position may be determined by identifying the sensor output with the known coating pattern.

11. The method of claim 9 in which the sensible coating is patterned in a regular manner along the length of the wire and wire position may be determined by detecting and counting the resulting regular variations in sensor output and identifying such regular sensor variations with a like number of coating variations.

12. The method of claim 8 in which the sensor is one or more of a magnetic, optical or capacitive sensor.

13. The method of claim 8 in which the sensible coating is of variable thickness for providing a signal of varying intensity reflective of the movement of the actuator in the article of manufacture.

14. The method of claim 8 in which the sensible coating is of variable composition for providing a signal of varying intensity reflective of the movement of the actuator in the article of manufacture.

15. A system for controlling the position of a substantially reversibly deployable device in an article of manufacture, the system comprising:

a linear shape memory alloy element as an actuator, the element comprising a formed sensible coating on a selected surface region of the element, the coating being of a composition that is formed on the surface so as to provide a detectable signal reflective of movement of the deployable device;

the shape memory alloy element being fixedly attached at one end and attached to the deployable device at a second end;

a sensor suitable for sensing the detectable characteristic in the sensible layer and providing an output signal;

a power supply for supplying electrical power to the shape memory alloy element to enable resistance heating of the shape memory alloy wire;

a controller for interpreting the sensor output signal to determine the wire motion and for relating the sensed motion of the wire to the deployable device position, and for adjusting the current supplied to the shape memory alloy by the power supply, to achieve predetermined positioning of the deployable device.

16. The system of claim 15 in which the linear shape memory alloy element is one or more of a wire, a strip, a cable, a braid and a chain.

17. The system of claim 15 in which the sensible coating is formed in a pattern of coating segments for providing a sequenced of signals reflective of the movement of the actuator in the article of manufacture

18. The system of claim 15 in which the sensible coating is metallic and deposited from aqueous solution.

19. The system of claim 15 in which the metallic coating is ferromagnetic.

20. The system of claim 15 in which the sensor is one of magnetic, capacitive or optical.