STIFFNESS CONTROL USING SMART ACTUATORS

• US 20120018962A1
• Filed: 07/22/2010
• Published: 01/26/2012
• Est. Priority Date: 07/22/2010
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations Incorporated (Motors Liquidation Co. GUC Trust)
• Inventors: Buravalla, Vidyashankar R., AC, Shivaram, Thakare, Amol G., Suryanarayan, Srinivasan
• Granted Patent: US 8,313,108 B2
• Time in Patent Office: Days
• US Class Current: 280/5.5
• CPC Class Codes: B60G 17/021 the mechanical spring being a coil spring B60G17/0272 takes precedence
• CPC Class Codes: B60G 17/025 the mechanical spring being a torsion spring B60G17/0277, B60G21/0553 take precedence
• CPC Class Codes: B60G 2202/42 Electric actuator
• CPC Class Codes: F16F 2224/0258 Shape-memory metals, e.g. Ni-Ti alloys
• CPC Class Codes: F16F 3/04 composed only of wound springs
• CPC Class Codes: F16F 7/082 and characterised by damping force adjustment means

Abstract

A stiffness control system and apparatus includes one or more stiffness elements which are each activated by a smart actuator including a smart material which may be one of a shape memory alloy (SMA), a magnetorheological (MR) fluid, an electrorheological (ER) fluid, and a piezo-stack. The stiffness control system includes a first and second interface adaptable to transmit input loads and a plurality of stiffness elements. A first stiffness element is operatively connected to the first and second interfaces and is continuously responsive to a change in system operating characteristics including input loads. A second stiffness element is selectively activated by the smart actuator so as to selectively respond to a change in system conditions. The continuous response of the first stiffness element can be selectively combined with the activated response of the second stiffness element to dynamically control system stiffness.

Claims

1. A stiffness control system, the system comprising:

a first interface adaptable to transmit a first input load;

a second interface adaptable to transmit a second input load;

a first stiffness element operatively connected to the first interface and the second interface, wherein the first stiffness element is configured to be continuously responsive to a change in the first and second input loads;

a second stiffness element including an actuator;

wherein the actuator includes a smart material configured such that actuation of the smart material activates the second stiffness element;

wherein the second stiffness element is configured in combination with the first stiffness element such that the second stiffness element is responsive to the change in the first and second input loads when activated.

2. The actuator of claim 1, wherein the smart material is a shape memory alloy (SMA) defining one of a SMA wire and a SMA spring.

3. The system of claim 1, wherein the actuator further comprises:

an actuator body defining an actuable portion;

an actuating mechanism defined by the smart material; and

an interfacing member;

wherein the actuable portion and the interfacing member define a slidable interface when the actuating mechanism is non-actuated; and

wherein the actuable portion and the interfacing member are in operative contact such that movement of the interfacing member relative to the actuator body is prevented when the actuating mechanism is actuated.

4. The actuator of claim 3, further comprising:

a friction element;

wherein the friction element is operatively connected to the actuable portion; and

wherein actuation of the actuating mechanism causes the friction element to operatively contact the interfacing member preventing movement of the interfacing member relative to the actuator body relative to each other.

5. The system of claim 1 further comprising:

an actuating source in operative communication with the actuator and configured to selectively actuate the smart material in response to the change in the first and second input loads.

6. The system of claim 5,

wherein the actuating source is an electrical current provided by one of a sensor, a controller, a switch and a combination thereof.

7. The system of claim 1,

wherein the first stiffness element includes at least one of a primary spring and a damper;

wherein the second stiffness element includes a secondary spring which is operatively connected to the first interface and the second interface when the actuator is actuated; and

is operatively disconnected from one of the first interface and the second interface when the actuator is not actuated.

8. The system of claim 1,

wherein the first stiffness element defines a primary torsion bar;

wherein the second stiffness element defines a secondary torsion bar which is selectively connected to the first interface and the second interface when the actuator is actuated.

9. The system of claim 8, wherein the secondary torsion bar comprises:

a first torsion bar segment operatively connected to the first interface;

a second torsion bar segment operatively connected to the second interface; and

wherein the actuator is configured as one of a coupling and a torque limiting device, such that the first torsion bar segment and the second torsion bar segment are selectively connected to each other when the actuator is actuated.

10. The system of claim 1, further comprising:

a third stiffness element including an actuator wherein the actuator includes a smart material;

wherein the third stiffness element is activated by the actuator;

wherein the actuator includes a smart material configured such that actuation of the smart material activates the third stiffness element;

wherein the third stiffness element is configured such that the third stiffness element is responsive to the change in the first and second input loads when activated.

11. An actuator comprising:

an actuator body defining an actuable portion;

an actuating mechanism including a smart material; and

an interfacing member;

wherein the actuable portion and the interfacing member define a slidable interface when the actuating mechanism is non-actuated; and

wherein the actuable portion operatively contacts the interfacing member when the actuating mechanism is actuated such that movement of the interfacing member relative to the actuator body is prevented.

12. The actuator of claim 11, further comprising:

a stiffness element;

wherein the actuation of the actuating mechanism activates the stiffness element.

13. The actuator of claim 12, wherein the stiffness element is configured as one of a spring, a coupling, and a torque limiter.

14. The actuator of claim 11, wherein the interfacing member defines one of a spring holder, a coupling interface and a clutch face.

15. The actuator of claim 11, wherein the smart material is a shape memory alloy (SMA) defining one of a wire and a spring.

16. The actuator of claim 11, wherein the smart material is one of a magnetorheological (MR) material, an electrorheological (ER) material, a piezo-element, a piezo-stack, a magnetic shape memory alloy (MSMA), and a magnetostrictive material.

17. The actuator of claim 11, further comprising:

a friction element;

wherein the friction element is operatively connected to the actuable portion; and

wherein actuation of the actuating mechanism causes the friction element to operatively contact the interfacing member preventing movement of the interfacing member relative to the actuator body.

18. A method for controlling the stiffness of a load transmitting system;

the method comprising;

providing a first stiffness element;

operatively connecting the first stiffness element to a first system interface and to a second system interface, such that load transmitted through the first system interface and the second system interface is transmitted through the first stiffness element;

providing a continuous response to the transmitted load from the first stiffness element;

providing a second stiffness element including an actuator, wherein the actuator includes a smart material configured such that actuation of the smart material activates the second stiffness element;

selectively activating the second stiffness element actuating the actuator, such that load transmitted through the first system interface and the second system interface is transmitted through the second stiffness element; and

providing a combined response to the transmitted load from the first stiffness element and the second stiffness element when the actuator is actuated.

19. The method of claim 18, further comprising:

sensing a change in the transmitted load;

activating and de-activating the second stiffness element in response to the change in the transmitted load, such that the stiffness of the system is dynamically changed in response to changes in the transmitted load.

20. The method of claim 18, wherein the load transmitting system is adaptable to the suspension system of a vehicle.