Smart material electro-hydraulic actuators use hydraulic rectification by one-way check valves to amplify the motion of smart materials, such as magnetostrictives and piezoelectrics, in order to create compact, lightweight actuators. A piston pump driven by a smart material is combined with a hydraulic cylinder to form a self-contained, power-by-wire actuator that can be used in place of a conventional hydraulic system without the need for hydraulic lines and a centralized pump. The performance of an experimental actuator driven by a 12.7 mm diameter, 114 mm length Terfenol-D rod is evaluated over a range of applied input frequencies, loads, and currents. The peak performance achieved is 37 W, moving a 220 N load at a rate of 17 cm/s and producing a blocked pressure of 12.5 MPa. Additional tests are conducted to quantify the dynamic behavior of the one-way reed valves using a scanning laser vibrometer to identify the frequency response of the reeds and the effect of the valve seat and fluid mass loading. A lumped-parameter model is developed for the system that includes valve inertia and fluid response nonlinearities, and the model results are compared with the experimental data.
Smart material electro-hydraulic actuators utilize fluid rectification by one-way valves to convert the small, high-frequency,
high-force motions of smart materials such as piezoelectrics and magnetostrictives into useful motions of a hydraulic
cylinder. These actuators have potential to replace centralized hydraulic pumps and lines with lightweight, compact,
power-by-wire systems. This paper presents the design and testing of an improved actuator system. To increase the
frequency bandwidth of operation, a lumped-parameter model is developed and validated based on experimental study of a
pump with a performance capacity of 18.4 W. The critical parameters for pump performance are identified and their effect
on pump performance assessed. The geometry of the hydraulic manifold that integrates the smart material pump and the
output hydraulic cylinder is found to be critical for determining the effective system bandwidth.
This paper presents two approaches to developing improved check valves for high frequency fluid rectification in
a smart material electro-hydraulic actuator: a single reed-type design and an array of miniaturized valves. The
multiphysics software COMSOL was used to study the 3-D fluid-structure interaction between the valve and
hydraulic fluid during pump operation, and the results were validated utilizing an instrumented valve to measure
in-situ tip displacement. The added mass effect of the fluid on the valve was experimentally characterized.
To improve the frequency response of the valves, an array of miniature reed valves were designed for the high
frequency and high pressure environment in the pump. A fabrication method was developed for the miniaturized
valves utilizing micromachining processes. The performance of the two types of valves was compared through
static and dynamic experiments.
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