Dissertation Defense: Design of a Magnetostrictive-Hydraulic Actuator Considering Nonlinear System Dynamics and Fluid-Structure Coupling

Committee:

• Professor Marcelo J. Dapino,  Chair (ME)
• Professor Ahmet Selamet (ME)
• Professor Rajendra Singh (ME)
• Professor Vishnu Baba Sundaresan (ME)

Summary:

Smart material electro-hydraulic actuators (EHAs) utilize fluid rectification via one-way check valves to amplify the small, high-frequency vibrations of certain smart materials into large motions of a hydraulic cylinder. Although the concept has been demonstrated in previously, the operating frequency of smart material EHA systems has been limited to a small fraction of the available bandwidth of the driver materials. The focus of this work is to characterize and model the mechanical performance of a magnetostrictive EHA considering key system components: rectification valves, smart material driver, and fluid-system components, leading to an improved actuator design relative to prior work.

A lumped-parameter modeling approach was applied to model the overall behavior of a magnetostrictive EHA, incorporating models for the reed valve response, nonlinear magnetostrictive behavior, and fluid behavior (including inertia and compliance). This model was validated by experimental study of a magnetostrictive EHA with a reduced volume manifold. The model was subsequently applied to design a compact magnetostrictive EHA for aircraft applications.

Testing of the system shows that the output performance increases with frequency up to a peak unloaded flow rate of 100~cm$^3$/s (6.4~cu~in/s) at 1200~Hz, which is a (100-500\%) increase over previous state-of-the-art systems. A blocked differential pressure of 12.1~MPa (1750~psi) was measured, resulting in a power capacity of 310~W, more than 100~W higher than previously reported values. The design and modeling approach used to scale up the performance to create a compact aircraft EHA can also be applied to reduce the size and weight of smart material EHAs for lower power level applications.