Research Papers

Experimental Validation of a Hybrid Electrostrictive Hydraulic Actuator Analysis

[+] Author and Article Information
Anirban Chaudhuri

Department of Aerospace Engineering, University of Maryland, College Park, MD 20742anirban@umd.edu

Norman M. Wereley1

Department of Aerospace Engineering, University of Maryland, College Park, MD 20742wereley@umd.edu


Corresponding author.

J. Vib. Acoust 132(2), 021006 (Mar 16, 2010) (11 pages) doi:10.1115/1.4000778 History: Received January 23, 2009; Revised October 29, 2009; Published March 16, 2010; Online March 16, 2010

The basic operation of smart material-based hybrid electrohydraulic actuators involves high frequency bidirectional length change in an active material stack (or rod) that is converted to unidirectional motion of a hydraulic fluid by a set of valves. In this study, we present the design and measured performance of a compact hybrid actuation system driven by the single-crystal electrostrictive material PMN-32%PT. The active material was actuated at different frequencies with variations in the applied voltage, fluid bias pressure, and external load to study the effects on output velocity. The maximum actuator velocity was 330 mm/s and the corresponding flow rate was 42.5 cc/s; the blocked force of the actuator was 63 N. The results of the experiments are presented and compared with simulation data to validate a nonlinear time-domain model. Linearized equations were used to represent the active material while the inertia, viscous losses, and compressibility of the fluid were included using differential equations. Factors affecting system performance are identified and the inclusion of fluid inertia in the model is also justified.

Copyright © 2010 by American Society of Mechanical Engineers
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Figure 1

Models for hybrid electrohydraulic actuation systems; a full (or half) circle means that the corresponding feature was included completely (or partly) in the model while an empty box refers to absence of that property in the formulation

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Figure 2

Schematic of hybrid actuator unidirectional test setup with PMN-PT stack

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Figure 3

Required stack lengths (La) and diameters (Da) for two different pumping frequencies (500 Hz and 700 Hz) with specific no-load velocity and blocked force requirements, calculated for different chamber diameters (Dch) under ideal quasi-steady conditions

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Figure 4

PMN-PT stack induced-strain measurements with static excitation

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Figure 5

Results of dynamic tests with 7 mm diameter PMN-PT stacks: (a) variation of induced-strain with frequency at different voltages, and (b) hysteresis in PMN-PT material at high frequencies

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Figure 6

Sectional view of the hybrid pump parts: (a) pump body with pre-stress mechanism; the PMN-PT stack (not shown) was placed between the insulating Delrin caps during testing and (b) pump head assembly with discharge and intake reed ports

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Figure 7

Test setup for PMN-PT actuator with external loads

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Figure 8

Comparison of actual strain in PMN-PT stacks and pump piston displacement at 500 Hz actuating frequency

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Figure 9

Measured mechanical parameters from no-load tests at different pumping frequencies and bias pressures: (a) output velocity, (b) induced-strain (peak-to-peak), and (c) manifold fluid pressure (peak-to-peak)

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Figure 10

Measured electrical parameters from no-load tests at different pumping frequencies: (a) peak voltage applied to stacks, and (b) output current from amplifier

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Figure 11

Measured output velocity from load tests at different pumping frequencies; nominal applied voltage=400 V, bias pressure=1.4 MPa (200 psi)

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Figure 12

(a) Force-velocity diagrams and (b) output power and efficiency plots for hybrid actuator

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Figure 13

Comparison of measured output velocities with simulation results at different voltage levels and bias pressures: (a) 300 V and (b) 400 V peak applied voltage

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Figure 14

Comparison of time-domain data at 600 Hz pumping frequency and 400 V peak applied voltage with simulation results: (a) induced-strain in PMN stack and (b) fluid pressure in manifold

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Figure 15

Comparison of measured output velocity (with external loads) and simulation results at different pumping frequencies

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Figure 16

Simulation results with different models: (a) 300 V and (b) 400 V peak applied voltage




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