HYDRAULIC ACTUATORS USING MAGNETOSTRICTIVE AND ELECTROSTRICTIVE MATERIALS ...

345 Pages·2008·15.35 MB·English

ABSTRACT
Title of dissertation: SELF–CONTAINED HYBRID ELECTRO-
HYDRAULIC ACTUATORS USING
MAGNETOSTRICTIVE AND
ELECTROSTRICTIVE MATERIALS
Anirban Chaudhuri, Doctor of Philosophy, 2008
Dissertation directed by: Professor Norman M. Wereley
Department of Aerospace Engineering
Hybrid electro-hydraulic actuators using smart materials along with flow rec-
tification have been widely reported in recent years. The basic operation of these
actuators involves high frequency bidirectional operation of an active material that
is converted into unidirectional fluid motion by a set of valves. While theoretically
attractive, practical constraints limit the efficacy of the solid-fluid hybrid actuation
approach. In particular, inertial loads, fluid viscosity and compressibility combine
with loss mechanisms inherent in the active material to limit the effective bandwidth
of the driving actuator and the total output power. A hybrid actuator was developed
by using magnetostrictive TerFeNOL-D as the active driving element and hydraulic
oil as the working fluid. Tests, both with and without an external load, were carried
out to measure the unidirectional performance of the actuator at different pumping
frequencies and operating conditions. The maximum no-load output velocity was 84
mm/s with a 51 mm long rod and 88 mm/s with a 102 mm long rod, both noted
around325Hzpumpingfrequency, whiletheblockedforcewascloseto89N.Dynamic
tests were performed to analyze the axial vibration characteristics of the Terfenol-D
rods and frequency responses of the magnetic circuits. A second prototype actuator
employing the same actuation principle was then designed by using the electrostric-
tive material PMN-32%PT as the driving element. Tests were conducted to measure
the actuator performance for varying electrical input conditions and fluid bias pres-
sures. The peak output velocity obtained was 330 mm/s while the blocked force was
63 N. The maximum volume flow rate obtained with the PMN-based actuator was
more than double that obtained from the Terfenol-D–based actuator.
Theoretical modeling of the dynamics of the coupled structural-hydraulic sys-
tem is extremely complex and several models have been proposed earlier. At high
pumping frequencies, the fluid inertia dominates the viscous effects and the prob-
lem becomes unsteady in nature. Due to high pressures inside the actuator and the
presence of entrained air, compressibility of the hydraulic fluid is important. A new
mathematical model of the hydraulic hybrid actuator was formulated in time-domain
to show the basic operational principle under varying operating conditions and to
capture the phenomena affecting system performance. Linear induced strain behav-
ior was assumed to model the active material. Governing equations for the moving
parts were obtained from force equilibrium considerations, while the coupled inertia-
compliance of the fluid passages was represented by a lumped parameter approach
to the transmission line model, giving rise to strongly coupled ordinary differential
equations. Compressibility of the working fluid was incorporated by using the bulk
modulus. The model was then validated using the measured performance of both the
magnetostrictive and electrostrictive-based hybrid actuators.
Self-Contained Hybrid Electro-Hydraulic Actuators using
Magnetostrictive and Electrostrictive Materials
by
Anirban Chaudhuri
Dissertation submitted to the Faculty of the Graduate School of the
University of Maryland, College Park in partial fulfillment
of the requirements for the degree of
Doctor of Philosophy
2008
Advisory Committee:
Dr. Norman M. Wereley, Chair/Advisor
Dr. Alison Flatau
Dr. Christopher Cadou
Dr. Robert M. Sanner
Dr. Balakumar Balachandran
(cid:13)c Copyright by
Anirban Chaudhuri
2008
DEDICATION
To my parents
and
all my teachers.
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“It is difficult to say what is impossible, for the dream of yesterday is the hope of
today and the reality of tomorrow.”
- Robert H. Goddard
“The greatest challenge to any thinker is stating the problem in a way that will allow
a solution.”
- Bertrand Russell
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Acknowledgments
I would like to gratefully acknowledge the contributions of my advisor, Dr.
Norman Wereley, towards the successful completion of my research. He has been the
ideal mentor to me; he encouraged my ideas, gave me enormous freedom to try out
different approaches during both the experimental stages and the theoretical work,
and was always available to discuss the progress of my research. His caring attitude
towards all students is exemplary. I would also like to thank the members of my
dissertation committee: Dr. Alison Flatau, Dr. Christopher Cadou, Dr. Robert
Sanner and Dr. Balakumar Balachandran. They took keen interest in my work and
provided valuable insights into my research, all of which resulted in an organized and
complete dissertation.
The work presented in this dissertation would not have been complete without
contributions from my colleagues at the University of Maryland. I would like to
acknowledgethehelpfromDr. Jin-HyeongYoo, whoacquaintedmewiththeactuator
designs and worked with me during the first stage of testing. His inputs have been
invaluable and I have learnt a lot about practical mechanical design from him. I
would also like to thank Dr. Shaju John for introducing me to rheology; he had great
faith in the model that I later developed and played an important role in tailoring
it for MR-based devices. I would also like to thank Michael Perna of the machine
shop for his help in fabrication of the numerous actuator parts. I also appreciate the
advice from Dr. Jayant Sirohi regarding the theoretical model.
ImadeseveralnewfriendsduringmystayatMarylandandtheircompanionship
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madesurethatgraduatestudentlifedidnotbecome“allworkandnoplay”. Aspecial
word of thanks to all my outstanding officemates - Dr. Wei Hu, Ben Woods, Nick
Wilson, Ted Bubert, Robbie Vocke, Dr. Atulasimha Jayasimha, Supratik Datta,
Dr. Greg Hiemenz, Grum Gnatu, Amy Ahure, Min Mao, Chaitanya Mudivarthi, Dr.
Keejoo Lee and Dr. Young Tai Choi - you have all helped me from time to time and
also livened up the lab. The helicopter design experience will never be forgotten - Ben
Hein, Nick Rosenfeld, the Eric trio (Parsons, Schroeder and Silberg), Tim Beasman,
Anne Brindejonc, Dr. Nagaraj, Dr. Tischenko and Dr. Inderjit Chopra - I learnt a
lot from all of you. Shishir Murarka and Ayan Sengupta were my apartment-mates
during the bachelor days and they are two of my closest friends today.
I gratefully acknowledge the financial support from the project sponsors: US
ArmyResearchOfficeunderaPhase2STTRcontract(Dr. GaryAnderson, Technical
Monitor), the US Army Aviation Applied Technology Directorate under a Phase 1
SBIR Contract (Dr. Louis Centolanza, Technical Monitor) and the Office of Naval
Research MURI grant (Jan Lindberg, Technical Monitor). I am also thankful to Dr.
Gang Wang and Dr. Peter Chen of Techno-Sciences, Inc., for their help.
My family has provided strong emotional and mental support during all my
years as a graduate student. This dissertation is dedicated to my parents who made
me a confident person and inspired me to always work with dedication and patience.
They instilled a strong sense of independence in me and supported all my career
decisions. My younger brother, Apu, maintains an excellent mix of studies and extra-
curricular activities and inspired me to do the same. My wife, Sneha, is my endless
source of motivation; her love and care have kept me strong and focused all these
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years. Although she denies it, she deserves an equal share of the sense of achievement
at the completion of the dissertation and I am truly fortunate to have her by my side.
We did it !!
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Table of Contents
List of Figures x
List of Tables xvi
List of Notations xvi
1 Introduction 1
1.1 Smart materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
1.1.1 Magnetostrictives . . . . . . . . . . . . . . . . . . . . . . . . . 17
1.1.2 Electrostrictives . . . . . . . . . . . . . . . . . . . . . . . . . . 23
1.2 Survey of smart actuator models . . . . . . . . . . . . . . . . . . . . . 31
1.2.1 Modeling of active material behavior . . . . . . . . . . . . . . 32
1.2.2 Static and quasi-static models . . . . . . . . . . . . . . . . . . 45
1.2.3 Dynamic actuator models in frequency domain . . . . . . . . . 52
1.2.4 Dynamic actuator models in time domain . . . . . . . . . . . 61
1.2.5 Use of CFD . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
1.3 Motivation and objectives of current research . . . . . . . . . . . . . . 68
1.4 Outline of Dissertation . . . . . . . . . . . . . . . . . . . . . . . . . . 71
2 Design and Testing of a Magnetostrictive Hydraulic Actuator 73
2.1 Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
2.2 Actuator Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
2.3 Experimental Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
2.3.1 Hybrid Pump . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
2.3.2 Input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
2.4 Test Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
2.4.1 No-Load Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
2.4.2 External Load Tests . . . . . . . . . . . . . . . . . . . . . . . 98
2.4.3 Characteristics of Driving Magnetic Circuit . . . . . . . . . . 103
2.5 Dynamic Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
2.5.1 Experimental Data . . . . . . . . . . . . . . . . . . . . . . . . 106
2.5.2 Magnetic path calculations . . . . . . . . . . . . . . . . . . . . 113
2.5.2.1 Reluctance method . . . . . . . . . . . . . . . . . . . 113
2.5.2.2 FEA of Magnetic Circuit . . . . . . . . . . . . . . . . 116
2.6 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
3 Dynamic Modeling of a Hybrid Electro-Hydraulic Actuator 121
3.1 Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
3.2 Actuator Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130
3.3 Characteristics of Driving Magnetic Circuit . . . . . . . . . . . . . . . 133
3.4 System Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135
3.4.1 Pump piston and Output piston . . . . . . . . . . . . . . . . . 135
3.4.2 Pumping chamber and output cylinder . . . . . . . . . . . . . 141
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