摘要:
Shape memory alloy (SMA) actuating elements are commonly simpler and of lower mass than alternative actuator designs and may find particular application in the transportation industry. Such SMA-powered devices are usually reliable and long-lived but the phase transformations which occur in the SMA alloy and are responsible for its utility are not totally reversible. This irreversibility, a consequence of irrecoverable strain, may progressively degrade the long-term actuator performance as the irrecoverable strain accumulates over many operating cycles. Methods and devices for compensating for these effects and extending the useful cycle life of SMA actuators are described.
摘要:
Shape memory alloy (SMA) actuating elements are commonly simpler and of lower mass than alternative actuator designs and may find particular application in the transportation industry. Such SMA-powered devices are usually reliable and long-lived but the phase transformations which occur in the SMA alloy and are responsible for its utility are not totally reversible. This irreversibility, a consequence of irrecoverable strain, may progressively degrade the long-term actuator performance as the irrecoverable strain accumulates over many operating cycles. Methods and devices for compensating for these effects and extending the useful cycle life of SMA actuators are described.
摘要:
Mechanical devices powered by Shape Memory Alloy (SMA) wires or other linear elements offer advantages in automotive applications. Such SMA-powered devices are commonly reliable and long-lived but have a finite lifetime. Measurements of the electrical resistivity of an SMA element during operation of the element may be related to the remaining lifetime of the element. Because operation of SMA elements is promoted by heating the element, usually by passage of an electric current, the resistivity measurements, and hence assessment of SMA element operation, may be made without interruption to the operation of the SMA-powered device and without addition of dedicated sensors.
摘要:
An energy harvesting system includes a heat engine and a component. The heat engine includes a belt, a first member, and a second member. The belt includes a strip of material and at least one wire at least partially embedded longitudinally in the strip of material. The wire includes a shape memory alloy material. A localized region of the at least one wire is configured to change crystallographic phase between martensite and austenite and either contract or expand longitudinally in response to exposure to a first temperature or a second temperature such that the strip of material corresponding to the localized region also contracts or expands. The first member is operatively connected to the belt and moves with the belt in response to the expansion or contraction of the belt. The component is operatively connected to the first member such that movement of the first member drives the component.
摘要:
An actuator includes a thermally activated active material member, and an external element configured to selectively engage the member and presenting a predetermined rate of thermal conductivity configured to transfer heat energy to and/or from the member, so as to reduce the actuation period or rate of cooling after actuation, when engaged.
摘要:
An overheating protection system adapted for use with a shape memory alloy actuator element, includes at least one switching shape memory alloy element presenting a slower activation period than that of the actuator element, and configured to selectively prevent activation of the actuator element, when the actuator element is actually or predicted to be experiencing overheating; and a circuit comprising the system, wherein the switching element and/or a circuit implement functions to modify activation of the actuator element.
摘要:
An actuator includes a thermally activated active material member, and an external element configured to selectively engage the member and presenting a predetermined rate of thermal conductivity configured to transfer heat energy to and/or from the member, so as to reduce the actuation period or rate of cooling after actuation, when engaged.
摘要:
A system for and method of reducing the effects of preheat period variation in shape memory alloy actuation, include sensing the removal of motion delay due to slack, backlash, and/or compliance in the actuator and drive-train of the system, and determining actuator activation, as a result thereof.
摘要:
Systems for and methods of determining at least one mid-stroke position of an active material actuated load by causing a stress induced rapid change in electrical resistance within the active material element, or modifying an ancillary circuit, when the load is at the mid-stroke position(s).
摘要:
A method of controlling and/or predicting the remaining useful life of an active material actuator, such as a shape memory alloy wire, includes obtaining historical actuation data of an inherent system variable, such as electrical resistance, over a secondary variable, such as time, determining a normal operating envelope having upper and lower bounds based on the data, determining a current profile for a given actuation cycle, and comparing the shape of the current profile to the envelope to determine an out-of-bounds event.