Parker-hannifin Corporation

Viking Technologies, L.c.

Keith A Thornhill

Jeff Moler

Mark Oudshoorn

John A Bugel

Jeffery B Moler

Aaron Dickey

An apparatus and process for preloading an electrically stimulated smart material actuator product to obtain maximum work from the actuator. When a smart material actuator is optimally preloaded certain desirable characteristics become apparent, such as work, operational frequency, hysteresis, repeatability, and overall accuracy. When used in conjunction with a mechanically leveraged actuator structure the smart material actuator can be used to its greatest potential. Since the mechanically leveraged actuator can be based on the maximum work provided by the smart material actuator, certain attributes such as the force, and displacement of total system can be adjusted without loss to system efficiency. Preloading methods and a determination of the optimal preload force are disclosed. Each smart material actuator type has a unique work curve. In the design of an actuator assembly, the process of optimizing uses the unique work curve to optimize the design for the requirements of the particular application. The unique work curve is used by finding the place where the smart material actuator is capable of providing the most work in order to set the optimum preload point accordingly. Different mechanical preload techniques are provided.

Apparatus and process for optimizing work from a smart material actuator product

An apparatus and process for pre-loading an electrically stimulated smart material actuator product to obtain maximum work from the actuator. When a smart material actuator is optimally pre-loaded certain desirable characteristics become apparent, such as work, operational frequency, hysteresis, repeatability, and overall accuracy. When used in conjunction with a mechanically leveraged actuator structure the smart material actuator can be used to its greatest potential. Since the mechanically leveraged actuator can be based on the maximum work provided by the smart material actuator, certain attributes such as the force, and displacement of total system can be adjusted without loss to system efficiency. Pre-loading methods and a determination of the optimal pre-load force are disclosed. Each smart material actuator type has a unique work curve. In the design of an actuator assembly, the process of optimizing uses the unique work curve to optimize the design for the requirements of the particular application. The unique work curve is used by finding the place where the smart material actuator is capable of providing the most work in order to set the optimum pre-load point accordingly. Different mechanical pre-load techniques are provided.

The present invention includes a method of compensating for differences in the rate of thermal expansion in one or more elements of an electro-mechanical actuator. The electro-mechanical actuator can include one or more elements such as a piezoelectric ceramic multilayer actuator (CMA) and a mechanism to amplify the motion of the CMA. A difference in the rate of thermal expansion or coefficient of thermal expansion, CTE, between the materials in the CMA and the amplifying mechanism can cause the two components to vary in size at differing rates as the ambient temperature varies. Since the amplifying mechanism provides substantial amplification of the motion of the CMA, the relative variation in size of the components due to temperature can be translated by the amplifying mechanism as motion of the CMA. This can result in substantial motion of the amplifying mechanism. Replacing a mechanical element in the amplifying mechanism with an element having a different value for the CTE substantially reduces the difference in CTE of the materials, thereby reducing the thermally induced motion of the amplifying mechanism. Further, the material used and the means of interconnecting the replacement element in the amplification device for thermal compensation can maintain high rigidity of the CMA support structure, since the support structure transmits the motion and force of the CMA to the amplifying mechanism as well as applying a compressive preload to the CMA. Further, a high level of compressive preload force can be used as an additional part of the overall design process to adjust the degree of thermal compensation required.

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Sarasota, FL, United States of America

Keith A Thornhill