Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02269585 1999-04-22
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COMPACT ACTUATOR AND CONTROLLER
AND PUMPING APPARATUS FOR SAME
This invention pertains generally to fluidic actuators and, more particularly,
to compact fluidic actuators.
For many current applications, hydraulic power is still the preferred method
of gaining mechanical advantage. On air
vehicles, for example, hydraulic power provides the mechanical muscle to
operate loads such as primary controls, flaps, slats,
landing gear retraction and extension, brakes and steering, thrust reversers
and weapons bay doors. In other air vehicles, the power
from the engines is used to generate the fluid power. Hydraulic power
distribution typically involves routing fluid supply and
return lines to connect sources to loads throughout the airframe, often with
redundancy requirements to reduce vulnerability.
Unfortunately, in many of these applications, this power comes with the
penalties of high weight, size, large acoustic signature,
cost and maintenance due to the system's distributed nature and redundancy
requirements.
Current state-of the-art solutions that locate the pressure source near the
load use an electrical system as a power source.
Electrical systems are ubiquitous and flexible and power distribution wiring
is relatively small, lightweight and survivable compared
with fluid lines. In many of these systems, electrical power is converted to
fluid power using a conventional rotating electric motor
to drive a pump. These systems, while offering certain advantages, have
rotational inertia, bearings to wear out, current inrush,
sensitivity to low voltage and weight and bulk. Further, in most cases the
unidirectional pump output requires special valuing
to change output actuation direction.
Other systems utilizing electrical energy as a power source have pumps with
magnetostrictive drivers and passive inlet
and outlet valves. See, for example, U.S. Patent No. 5,520,522. Unfortunately,
these passive mechanical check valves have dynamics
that degrade their performance at high frequencies. Such valves also have a
single design operating pressure and do not allow
the same device to operate at either very low pressure or very high pressure.
Nor are these valves shown for use in a fluidic actuator.
U.S. Patent No. 5,501,425 separately discloses valves with magnetostrictive
drivers, but the emphasis is on fail-safe conditions
2 0 for two position solenoid valves. The patent does not disclose
incorporating such active valves into a pump or a fluidic actuator.
As can be seen from the foregoing, there is a need for a new and improved
fluidic actuator which overcomes these disadvantages.
In general, it is an object of the present invention to provide a compact
actuator which has a self contained fluid system.
Another object of the invention is to provide an actuator of the above
character which is easily scalable for different size
applications.
2 5 Another object of the invention is to provide an actuator of the above
character which provides hydraulic power with little
acoustic noise.
Another object of the invention is to provide an actuator of the above
character which Itas relatively few moving parts.
Another object of the invention is to provide an actuator of the above
character which uses electricity as a power source.
Another object of the invention is to provide an actuator of the above
character which has a relatively small volume of
3 0 fluid.
Another object of the invention is to provide an actuator of the above
character which provides an output of relatively long
stroke and high force.
Another object of the invention is to provide an actuator of the above
character which utilizes motors having smart material
actuation elements made from TERFENOL-D.
3 5 Another object of the invention is to provide a controller for operating
an actuator of the above character.
Another object of the invention is to provide a pumping apparatus for use with
an actuator of the above character which
utilizes the momentum of the pump piston to enhance the efficiency of inlet
and/or exhaust valves of the pump.
Additional objects and features of the invention will appear from the
following description from which the preferred
embodiments are set forth in detail in conjunction with the accompanying
drawings.
4 0 FIG. 1 is a fragmentary cross-sectional view of a portion of a wing
assembly utilizing the compact actuator of the present
invention.
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FIG. 2 is a perspective view of the compact actuator of FIG. 1.
FIG. 3 is a perspective view similar to FIG. 2 of the compact actuator of FIG.
1 which has been cut away at various portions.
FIG. 4 is a cross-sectional view taken along the line 4-4 of FIG. 2 of the
compact actuator of FIG. I.
FIG. 5 is a cross-sectional view taken along the line 5-5 of FIG. 2 of the
compact actuator of FIG. 1.
FIG. 6 is a schematic view of the compact actuator of FIG. 1.
FIG. 7 is another schematic view of compact actuator of FIG. 1.
FIG. 8 is a fragmentary view of another embodiment of a normally open flow
control valve for use with the compact actuator
of FIG. 1.
FIG. 9 is a fragmentary view, similar to FIG. 8, of another embodiment of a
normally closed flow control valve for use
with the compact actuator of FIG. 1.
FIG. 10 is a schematic view of another embodiment of the compact actuator of
the present invention.
FIG. 11 is a flow chart depicting the operation of the compact actuator of
FIG. 10.
FIG. 12 is a series of time synchronized graphs showing time histories of
sample input currents to the pump and flow control
valves of the compact actuator of FIG. 10.
FIG. 13 is a fragmentary view of another embodiment of a pump for use with the
compact actuator of FIG. 1.
FIG. 14 is a fragmentary view of a further embodiment of a pump for use with
the compact actuator of FIG. 1.
FIG. 15 is a fragmentary view of yet another embodiment of a pump for use with
the compact actuator of FIG. 1.
In general, a compact actuator for use with a fluid and including a housing
having a predetermined geometry is provided.
An actuation member is mounted in the housing for movement between first and
second positions for performing work. The actuation
2 0 member has first and second faces. Means within the housing provides fluid
to the first face for moving the actuation member
to the first position and to the second face for moving the actuation member
to the second position. Said means includes at least
one transducer having an active element and means for producing an
electromagnetic field which extends through at least a portion
of the active element. The active element is changeable between a first shape
when in the absence of the electromagnetic field
and a second shape when in the presence of the electromagnetic field. A
controller and pumping apparatus for use with the actuator
2 5 are provided.
More particularly, the self contained actuation apparatus 21 of the present
invention can be used with a conventional wing
22 as shown in the fragmentary view of FIG. 1. Wing 22 includes an air foil 23
having a flap 26 at the trailing edge thereof.
The segmented flap 26 has a forward portion 26a and an aft portion 26b
pivotally coupled to forward portion 26a. A guide pin
27 is connected to the aft portion 26b and rides within a track 28 for moving
the aft portion outwardly and downwardly from a
3 0 first or inline position shown in solid lines in FIG. 1 to a second or
deflected position shown in dashed lines in FIG. 1. One or
more actuators 21, one of which is shown in FIG. 1, is carried by forward
portion 26a for moving aft portion 26b between its
inline and deflected positions.
Compact actuation apparatus or solid state smart material actuator 21 has a
housing 31 formed with a predetermined geometry.
The shape of housing 31 can be tailored to fit in irregularly-shaped
envelopes. The housing 31 is made from any suitable material
3 5 such as hard anodized aluminum or steel and has a weight ranging from 0.1
to 200 pounds and preferably ranging from 20 to 30
pounds and an envelope or displaced volume ranging from 0.5 to 1000 in3 and
preferably ranging from 15 to 25 in3. The housing
31 shown in FIGS. 2-4 has a weight of less than five pounds. Housing 31 is
shaped as a parallelepiped, having a length, width
and depth of approximately six, two and two inches, respectively. The
segmented housing 31 is formed from a plurality of plate-like
members secured together by any suitable fastening means such as bolts and
nuts (not shown). These plate members include a
4 0 top plate 32, a second plate 33, a third plate 36 and a bottom plate 37.
The exterior of housing 31 is formed by outer surface 38.
An actuation member in the form of piston or ram 41 is slidably carried by
housing 31. Ram 41 is cylindrical in shape
and made from any suitable material such as steel or titanium. The ram 41 has
an enlarged head 42 formed integral with a rod
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43. The rod 43 has a threaded end 43a accessible from the exterior of housing
31 and is shown in FIG. 1 as being connected to
aft portion 26b of flap 26. Head 42 has tirst and second opposite planar faces
consisting of upper face or surface 46 and lower
face or surface 47. Rod 43 is joined to head 42 at lower surface 47. Third
plate 36 of housing 31 is provided with a cylindrical
bore or chamber 56 for slidably receiving ram head 42. As such, the
cylindrical internal surface of housing 31 forming chamber
56 is diametrically sized slightly larger than head 42. An access bore 57
extends through bottom plate 37 and communicates with
chamber 56. Rod 43 slidably extends through access bore 57. Conventional fluid
sealing means (not shown) is provided between
head 42 and the inner cylindrical surface of third plate 36 for inhibiting the
flow of fluid between surfaces 46 and 47 of ram 41.
Head 42 thus divides ram chamber 56 into first and second portions 56a and
56b. Similarly, conventional sealing means (not shown)
is provided between the outer surface of rod 43 and the inner cylindrical
surface forming bore 57 in bottom plate 37. As shown
most clearly in FIG. 5, ram 41 is movable between a first or extended
position, shown in solid lines in FIG. 5, and a second or
retracted position, shown in dashed lines in FIG. 5.
Self-contained fluid means or system 61 is provided within housing 31 and
coupled to ram 41 for causing movement of
the ram between its first and second positions. Fluid or hydraulic system 61
is shown schematically in FIGS. 6 and 7 and includes
at least one transducer for providing liquid to upper surface 46 of ram head
42 for moving ram 41 to the first position and,
alternatively, for providing liquid to lower surface 47 for moving ram 41 to
the second position. More specifically, hydraulic
system 61 includes a positive displacement pump 62, a first control valve 63
at the inlet of the pump 62 and a second control valve
64 at the outlet of the pump 62. Each of these three components has a
transducer therein. For example, Pump 62, as shown most
clearly in FIGS. 3 and 4 and schematically in FIG. 7, has a transducer or
motor 69 which includes a cylindrical actuation element
or piston 71. A suitable liquid for use in actuator 21 shown in FIGS. 2-5 is a
fire-resistant phosphate ester hydraulic fluid or a
2 0 petroleum based hydraulic fluid and the actuator 21 operates with a volume
of such liquid ranging from 0.05 to 1 liter and preferably
ranging from 0.20 to 0.25 titer. Liquid metals can also be used for the fluid
or liquid of actuator 21.
Piston or rod 71 is made from a suitable active or smart material which
changes shape when energized by being placed
in an electromagnetic field. Such materials can include electrostrictive
materials, piezoelectric materials and magnetostrictive
materials. A preferred electrostrictive material is lead magnesium niobate and
its variants and a preferred piezoelectric material
2 5 is lead zirconate titanate and its variants. Magnetostrictive materials
change shape in response to an applied magnetic field.
Specifically, rod 71 is changeable between a first or shortened shape when in
the absence of a magnetic field and a second or elongated
shape when in the presence of a magnetic field. A giant magnetostrictive
material is preferred because such a material can tolerate
high mechanical stress so as to have a relatively high energy density. High
energy density enables more mechanical power output
from a given electrical power input and volume of smart material which thus
reduces the size and weight of actuator 21. Preferred
3 0 giant magnetostrictive materials are rare earth materials, rare earth-
transition metal materials and compositions having rare earth
materials, transition metals and other elements.
Preferred rare earth materials for operating temperatures ranging from
0° to 200° K are rare earth binary alloys such as
TbxDy~_x, where x ranges from 0 to 1. Other rare earth elements can be added
or substituted for either terbium or dysprosium
in this base alloy. For example, holmium, erbium or gadolinium can be used in
place of either terbium or dysprosium. Other
3 5 preferred rare earth materials for operating temperatures ranging from
0° to 200° K are body centered cubic intertnetallic compounds
such as (TbxDyl_,~(Zrt~.Cd,.y), where x ranges from 0 to 1, y ranges from 0 to
1 and x + y = 1. Other rare earth elements, such
as holmium, erbium or gadolinium, can be added or substituted for either
terbium or dysprosium in these body centered cubic
intermetallic compounds.
Preferred rare earth-transition metal materials are rare earth-iron materials
such as TERFENOL based alloys. These alloys
4 0 are suited for operating temperatures ranging from 0° to
700° K. One of these alloys is TbFeZ. Particularly preferred rare earth-
iron
materials for operating in the 0° to 700° K temperature range
are disclosed in U.S. Patent Nos. 4,308,474; 4,609,402; 4,770,704;
4,849,034 or 4,818,304, incorporated herein by this reference, and include the
material known as TERFENOL-D sold by ETREMA
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Products, Inc. of Ames, Iowa. TERFENOL-D is a metal alloy formed from the
elements terbium, dysprosium and iron and
has the formula of TbXDy,_xFe2_w, where x ranges from 0 to 1 and w ranges from
0 to 1. A preferred formula for TERFENOL-D
is Tb,Dy,_XFes,~,_~5, where x ranges from 0.25 to 1Ø A particularly
preferred formula for the TERFENOL-D material of rod
71 is Tbo_3Dyo.,Fe,_~. Other rare earth materials, such as cerium,
praseodymium, neodymium, holmium, erbium or gadolinium,
can be added or substituted for terbium or dysprosium for property enhancement
purposes. For example, a giant magnetostrictive
material having the rare earth materials R'x,, Rz,~, R'x3 ... R ",can be
provided where R ; R Z R 3 .. R Constitute rare earth materials
and xl + x2 + x3 ... + xn = 1. Other transition metals, such as manganese,
cobalt or nickel, can be added or substituted for
iron as disclosed in U.S. Patent No. 5,110,376, incorporated herein by this
reference. Elements which are not transition metals,
such as aluminum, can also be added or substituted for iron. For example, a
giant magnetostrictive material having the elements
T'Y,, Tzy2, T3y3 ... T"y" can be provided where T', T2, T' ...T" constitute
transition metals or elements such as aluminum and yl
+ y2 + y3 ... + yn = 2-w, and w ranges from 0 to 1. Alternatively, an
intetmetallic compound can be provided having combinations
or variations of TERFENOL-D, such as (Tb%,,Dy,~,R3~,R",4 ...
R",")(FeY,,T2YZ,T'Y3 ... T"y")i_W where xl + x2 + x3 ... + xn =
1, yl + y2 + y3 ... + yn = 2-w, and w ranges from 0 to 1.
Giant magnetostrictive materials which contract and thus exhibit negative
magnetostriction when placed in a magnetic field
can be used for the material of rod 71 and be within the scope of the present
invention. These negative magnetostrictive materials
have formulations similar to the giant magnetostrictive materials described
above except that they include the rare earth element
samarium. Preferred negative magnetostrictive materials for operating
temperatures ranging from 0° to 700° K are SAMFENOL
based alloys such as SmFez. A particularly preferred SAMFENOL based alloy is
SAMFENOL-D, which is also disclosed in U.S.
Patent Nos. 4,308,474; 4,609,402; 4,770,704; 4,849,034 or 4,818,304 and has
the formula SmxDy,_~Fe2_W, where x ranges from
2 0 0 to 1 and w ranges from 0 to 1. Other rare earth materials, such as
cerium, praseodymium, neodymium, holmium, erbium or
gadolinium, can be added or substituted for samarium or dysprosium in the same
manner as discussed above with respect to
TERFENOL based alloys. In addition, other transition metals, such as
manganese, cobalt or nickel, and elements which are not
transition metals, such as aluminum, can be added or substituted for iron in
the same manner as also discussed above.
Means which includes coil 72 is provided in motor 69 for producing an
electromagnetic field which extends through at
2 5 least a portion of drive member or rod 71. Coil 72 is made from any
suitable material such as copper or aluminum and is
concentrically disposed about rod 71 for producing a magnetic field having a
flux which extends through the rod 71. Coil 72 is
mounted within third plate 36, as shown in FIG. 4. Rod 71 has an end 71a which
extends from one end of coil 72 to abut the center
of a diaphragm 76 made from any suitable material such as stainless steel. The
other end of rod 71 is secured to the inside of coil
72. Diaphragm 76 extends across an opening in the form of cylindrical bore 77
provided in third plate 36 and is generally cup-like
3 0 in shape. In this regard, diaphragm 76 extends upwardly from coil 72 at
its outer periphery to sealably secure to the third plate
36. A plate member or disk 81 made from any suitable material such as a
noncorrosive stainless steel alloy overlies diaphragm
76 and is sealably secured at its outer periphery to the diaphragm 76. In this
manner, disk 81 and diaphragm 76 form a pumping
chamber 82 therebetween.
Inlet and outlet check valves 63 and 64 respectively control the flow of
liquid into and out of pumping chamber 82 in a
3 5 single direction and are included within the means of actuator 21 for
selectively directing pressurized liquid between pump 62 and
ram 41. As shown in FIGS. 3 and 4 and schematically in FIG. 7, valves 63 and
64 have respective motors 83 and 84 which include
respective actuation elements in the form of rods or pistons 86 and 87 made
from any suitable material such as the materials discussed
above with respect to rod 71. Preferably, pistons or drive members 86 and 87
are each made from a magnetostrictive material
and more preferably from a giant magnetostrictive material such as TERFENOL-D.
Coils 88 and 89, each substantially similar
4 0 to coil 72, are included in motors 83 and 84 and are concentrically
mounted about respective pistons 86 and 87. Coils 88 and 89
serve to energize pistons 86 and 87 by producing a magnetic field which
extends through the pistons 86 and 87. First and second
amplifiers 91 and 92 are included within valves 63 and 64 for amplifying the
stroke of respective pistons 86 and 87 of motors 83
,r ,.
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and 84. Stroke amplifiers 91 and 92, not cross sectioned in the drawings, can
each be of any conventional type such as a hydraulic
stroke amplifier and preferably a Bernoulli-type stroke amplifier. Amplifiers
91 and 92 have respective output rods 93 and 94
sfidably carried therein and movable longitudinally as a function of the
longitudinal movement of respective pistons 86 and 87.
Inlet and outlet valves 63 and 64 and amplifiers 91 and 92 are disposed in
first and second spaced-apart bores 96 and 97 extending
downwardly into top plate 32 of housing 31.
Valves 63 and 64 each utilize a poppet valve configuration. Specifically, a
cylindrical member or valve rod 98 is secured
to the end of amplifier rod 93. The lower portion of valve rod 98 is formed as
a valve head 99. A cylindrical member or valve
rod 101 is similarly secured to the end of amplifier rod 94 of outlet valve
64. Valve rod 101 has a lower portion formed as a valve
head 102. Rods 98 and 101 are each made from any suitable material such as a
noncorrosive stainless steel alloy. Valve heads
or plugs 99 and 102 seat respectively in spaced-apart openings or orifices 103
and 104 provided in disk 81. The orifices 103 and
104 communicate with pumping chamber 82. Caps 106 and 107 are provided for
retaining inlet and outlet control valves 63 and
64 within top plate 32.
The elastic modulus of the smart material and the bulk modulus of the fluid
within system 61 determine the stiffness matching
geometry of pumping chamber 82 and the smart material driver or piston 71. The
maximum fluid power point (pressure and flow)
is optimized for a given electrical input, size, weight, thermal environment
and/or startup transient for actuator 21. Plugs 99 and
102 and orifices 103 and 104 are shaped and contoured to optimize fluid flow
characterization and thus maximize the performance
of actuator 21. In this regard, the maximized fluid power is matched with ram
41 so that the minimum and maximum physical
geometries of plugs 99 and 102 and oritices 103 and 104, as well as the
minimum and maximum physical geometries of pumping
chamber 82 and piston 71, can be determined. Additional design considerations
are the output pressure and flow and frequency
2 0 response over the desired temperature range.
Hydraulic system 61 further includes a spool valve or servo valve 111 which
serves as means for directing the flow of
liquid between inlet and outlet control valves 63 and 64 and the ram 41. Servo
valve 111 is shown in FIG. 5 and schematically
in FIG. 7. An inlet line 112 connects inlet control valve 63 to the servo
valve 111 and an outlet line 113 connects outlet control
valve 64 to the servo valve 11. First and second lines 116 and 117 connect the
servo valve 111 to respective first and second portions
2 5 56a arid 56b of ram chamber 56. Servo valve 111 has a central chamber 118
provided in top plate 32 which communicates with
each of lines 112 and 113 and lines 116 and 117. Chamber 118 is generally
cylindrical in shape. An elongate member or rod
121 made from any suitable materials such as steel or aluminum extends through
chamber 1 I 8. Rod 121 has first and second spaced-
apart spools 122 and 123 mounted thereon. Rod 121 is slidably disposed on
first and second bearing assemblies 126 and 127 carried
by top plate 32 at opposite ends of internal chamber 118. Rod 121 is
longitudinally movable within chamber 118 from a first position
3 0 shown in solid fines in FIG. 5 and in dashed lines in FIG. 7, in which
liquid is directed from line 113 to first line 116, and a second
position shown in solid Lines in FIG. 7, in which liquid is directed from line
113 to second line 117. When rod 121 is in its first
position, liquid returning from ram chamber second portion 56b by means of
second line 117 is directed to line 112. When rod
121 is in its second position, liquid returning from ram chamber first portion
56a by means of first line 116 is directed to the line
Z I2. For simplicity, not all of the hydraulic lines of fluid system 61 are
shown in FIGS. 2-5. The hydraulic Iines are milled into
3 5 housing 31.
Servo valve 111 includes means in the form of a transducer or motor 129 for
driving rod 121 between its first and second
longitudinal positions within chamber 118. Motor 129 includes a cylindrical
rod-like element in the form of actuation element
131 made from any suitable material such as the materials discussed above with
respect to rod 71. Preferably, actuation element
131 is made from a magnetostrictive material and more preferably from a giant
magnetostrictive material such as TERFENOL-D.
4 0 A coil 132 substantially similar to coil 72 is concentrically carried or
disposed about actuation element 131. An amplifier 133
is included within servo valve 111 for amplifying the stroke of actuation
element 131 of motor 129. Stroke amplifier 133, not
cross sectioned in the drawings, is of a conventional type and substantially
similar to stroke amplifiers 91 and 92. The amplifier
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has an output rod 134 slidably carried therein and movable longitudinally as a
function of the longitudinal movement of actuation
element 131. The output rod 134 has an end secured to one end of rod 121. Caps
136 and 137 are provided for respectively retaining
rod 121 and motor 129 within top plate 32.
Fluid system 61 in compact actuator 21 further includes a conventional high
pressure accumulator 138 and a conventional
low pressure reservoir 139, as shown schematically in FIGS. 6 and 7. Both high
pressure accumulator 138 and low pressure reservoir
139 are similar in configuration and have a temperature compensating variable
volume chamber 141 which is separated from a
fluid storage chamber 142 by a flexible membrane 143. Chamber 141 is filled
with pressurized gas for accommodating pressure
changes due to such factors as piston motion or thermal changes. Low pressure
liquid in fluid system 61 is routed to low pressure
reservoir 139 where it is ready for recycling through the fluid system. The
elements of each of high pressure accumulator 138
and tow pressure reservoir 139 are carried inside third plate 36 of housing
31, as shown in FIG. 5 with respect to low pressure
reservoir 139.
Electrical means in the form of control electronics or controller 146 is
electrically coupled to coils 72, 88-89 and 132.
The multiple-input, multiple-output controller is built from conventional off
the-shelf pans. As shown most clearly in FIGS. 6
and 7, electrical lead 147 couples controller 146 to pump motor 69 and leads
148 and 149 respectively couple the controller to
inlet and outlet control valve motors 83 and 84. The controller 146 is
electrically coupled to motor 129 of servo valve 111 by
means of lead 151. Controller 146 is provided with a power and signal
connector 152 accessible at the exterior of housing 31 for
permitting an external power supply 153 to be electrically coupled to
controller 146 and for permitting commanded signals to be
provided to the controller and other electrical communications therewith. The
controller 146 contains power conditioning electronics
for directing electrical energy to the coils and thus causing each of the
coils to generate an electromagnetic and specifically a magnetic
2 0 field around the coil. The magnetic fields actuate and thus control the
movement of the respective actuation elements.
Sensing or measuring means is carried by housing 31 for determining tire
external axial force being exerted on threaded
end 43a of ram 41 and the position of ram 41 within chamber 56. In this
regard, as shown in FIG. 6, a first pressure transducer
or sensor 161 communicates with first line 116 and a second pressure
transducer or sensor 162 communicates with second line
117 for determining the liquid pressure in such lines and thus the pressure in
first and second chamber portions 56a and 56b on
2 5 each side of ram head 42. The differential pressure across ram head 42 can
thus be determined by controller 146. Conventional
pressure sensors 161 and 162 can be of the type manufactured by Kulite
Tungsten Corporation of East Rutherford, New Jersey.
A position sensor in the form of a linear variable differential transformer or
stroke transducer 163 is carried by housing 31 and
coupled to ram 41 for determining the position of ram 41 and its threaded end
43a relative to housing 31. Conventional stroke
transducer 163 can be of the type manufactured by Trans-Tek, Inc. of
Ellington, Connecticut. Ram 41 includes a force sensor
3 0 in the form of a load cell or force transducer 164 disposed in the load
path between head 42 and rod 43 for determining the force
upon ram 41. Conventional force transducer 164 can be of the type manufactured
by Sensotec, Inc. of Columbus, Ohio. Transducers
161-163 and load cell 164 are electrically coupled to controller 146 by means
of electrical leads 166. Pressure sensing or measuring
means in the form of conventional pressure sensor 167 is carried by housing 31
and communicates with fluid storage chamber
142 of high pressure accumulator 138. Pressure sensor 167 is electrically
connected to controller 146 by electrical lead 168 for
3 5 permitting the pressure within accumulator 138 to be monitored by the
controller 146.
In operation and use, compact hydraulic actuator 21 can be used for moving or
pivoting aft portion 26b of flap 26 relative
to forward portion 26a of the flap and thus change the camber of wing 22. For
initiating movement of ram 41 and thus flap aft
portion 26b, the desired command signal is sent to controller 146 which in
turn supplies electrical energy to pump 62, inlet and
outlet control valve 63, 64 and servo valve 111 at the appropriate durations
and levels to cause these components to provide liquid
4 0 to either upper surface 46 or lower surface 47 of ram head 42 and thus
move ram 41 within chamber 56.
Controller 146 of actuator 21 can be electrically coupled by means of
connector 152 to any suitable computer such as a
personal computer (not shown). Actuator 21 can be electronically configured by
the personal computer to function in a prescribed
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manner for the given application. In this regard, the length of movement or
displacement of ram 41, the speed or velocity at which
the ram 41 is moved and the force that is available at threaded end 43a of ram
41 can be set. Other parameters of actuator 21 which
can be so set include: the characterization of the ram 41 in relation to the
input control signal to actuator 21, the response time
or acceleration of ram 41, the damping ratio of ram 41, the accuracy of the
desired position of ram 41, and the type of control
strategy (for example, phase-locked-loop or frequency-locked-loop) the
actuator 21 will execute and the functional parameters
of the control strategy. Additional actuator parameters which can be set
include the communications parameters (for example,
peer-to-peer, supervisory, report by exception, networked or stand alone), the
alarm and shutdown parameters such as operating
temperature limits on the internal diagnostics of actuator 21 and the database
parameters, alarm and event logs and user security
passwords of the actuator 21.
Actuator 21 can be programmed with a variety of failure modes for output ram
41 in the event of loss of electrical power
to the actuator. In a "lock-in-last position" failure mode, ram 41 is locked
in the position along its stroke length that it was in
at the time of loss of electrical power or control signal to actuator 21. This
is accomplished by closing both flow control valves
63 and 64 to prevent flow from occurring between the ram 41 and the pump 62.
Ram 41 is allowed to move freely to any position
along its stroke length upon loss of electrical power or control signal to
actuator 21 in a "move-to position" failure mode. This
is accomplished by opening both of valves 63 and 64 to enable flow to occur
between the ram 41 and pump 62. If a "fail-retracted"
failure mode is selected, ram 41 is forced to a zero (minimum) displacement
position along its stroke length by opening both of
valves 63 and 64 to permit flow between the ram 41 and pump 62 and by
providing a mechanical spring force (not shown) to push
the ram to its fully retracted position. In a "fail-extended" failure mode,
ram 41 is forced to its full (maximum) displacement position
along its stroke length. This is accomplished by opening both of valves 63 and
64 and by providing a mechanical spring force
2 0 (not shown) to push the ram to its fully extended position.
The operation of pump 62 and valves 63, 64 and 111 is substantially similar in
that these components are each activated
by an electrical signal from controller 146. Controller 146 operates at the
fixed frequency of a standard power supply, for example
400 Hz for an aircraft. Pump 62 and valves 63, 64 and 111 are each driven by
an actuation member made from TERFENOL-D.
These magnetostrictive actuation elements are changeable between a tirst
condition in the absence of a magnetic field and a second
2 5 elongated or extended condition in the presence of a magnetic field for
performing work in said components. The amount of elongation
of an actuation element is proportional to the amplitude of the electrical
current signal to actuation coil 72, 88-89 or 132 and the
resulting strength of the magnetic field generated by the coil. The frequency
of elongation corresponds to the frequency of the
electrical signal to the coil. For example, the energizing of coil 72 in pump
62 causes rod 71 to elongate and rod end 71a to move
diaphragm 76 toward disk 81 and thus pressurize the liquid within pumping
chamber 82. The cessation of electrical energy to
3 0 coil 72 causes rod 71 to contract and thus return diaphragm 76 to its home
position shown in FIG. 4. Likewise, normally open
inlet and outlet valve pistons 86 and 87 extend when respective coils 88 and
89 are energized by energy supplied to them by controller
146. Pistons 86 and 87 cause respective valve heads 99 and 102 to close and
seat within respective valve seat orifices 103 and
104 as shown in FIG. 4. Upon the cessation of electrical energy to coil 88 or
89, the corresponding valve head 99 or 102 unseats
from the respective orifice 103 or 104 to cause the control valve to open.
3 5 The drive current waveform provided to pump 62 and valves 63 and 64 is
controlled to provide the desired pressure in
hydraulic accumulator 138 and thus fluid system 61. The pump waveform is
obtained by modulating the desired direct current
amplitude signal with a fixed frequency sinusoid, producing a variable
amplitude, fixed frequency waveform. Increased performance
in the terms of pumping efficiency is obtained by driving pump 62 with an
electrical signal having a frequency equal to the mechanical
resonsant frequency of the pump 62. The resonant input signal to pump 62
amplifies the stroke of the pump to provide relatively
4 0 large stroke and pumping capacity. Thus, pump 62 provides relatively more
stroke for less energy than conventional pumps.
The mechanical resonant frequency of pump 62 is determined by the size and
weight of the magnetostrictive piston 71,
the amplitude of the drive signal to piston 71, the prestressing and other
mechanical loading of the piston 71. For a fixed pump
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design, the optimal resonant frequency is a function of both the power level
and the pump load characteristics, which can change
during operation. In the simplest implementation, the drive frequency is
fixed, thus requiring a tradeoff to determine the single
frequency that provides the best efficiency given the operation power levels
and pump load characteristics. Once the drive frequency
is chosen and fixed, the output of pump 62 is controlled by the amplitude of
the drive current to piston 71.
Pump 62 appears to the drive electronics or circuit as an inductor and a
resistor in series. Hence, the drive electronics
within controller 146 must supply both real and reactive power to pump motor
69. The efficiency of the drive electronics can
be increased if designed to advantageously use the inductive features of the
magnetrostrictive motor 69. In general, the drive
electronics consist of a sinusoidal voltage source in series with a capacitor.
The value of the capacitor is chosen to provide a resonant
circuit with the inductance of the magnetostrictive motor 69 when operated at
the mechanical resonant frequency of the pump 62.
That is, the capacitor is chosen to produce in conjunction with the inductance
of the magnetostrictive motor 69 an electronic resonance
at the desired drive frequency. In this case, the voltage source need only
provide real power, and not reactive power, to pump
62 so as to reduce the cost and increase the efficiency of the drive
electronics.
Alternate implementations of the drive electronics can use switched mode
electronics. In these cases, the drive electronics
can use the inductive load of pump motor 69 for power smoothing. Increased
performance and decreased cost can be obtained
by designing these switched-mode drive electronics for the specific load
characteristics of pump motor 69 and the chosen drive
frequency.
Pump 62 can operate at one frequency independent of the fluid demands within
actuator 21. As can be appreciated, for
a fixed surface area of piston head 42, the flow through pump 62 is determined
by the frequency and stroke length of the piston
head. When the frequency of the input signal to pump motor 69 is fixed, the
flow through the pump is thus determined by the
2 0 stroke length of the piston head 42. The stroke of pump 62 is a function
of the magnetic field strength applied by drive coil 72,
which is determined by the current in the coil 72. This current is a function
of the voltage across the drive coil 72 since the impedance
of drive coil 72 is generally constant at a fixed frequency. In this manner,
the power to pump 62 can be switched on and off at
the fixed frequency between zero volts and the control voltage to produce the
reciprocating stroke of the pump. As can be seen,
the foregoing simplifies power control to ON/OFF and flow control to voltage
control.
2 5 Inlet and outlet control valves 63 and 64 actively control the flow of
liquid from pump 62 to accumulator 138 and from
the reservoir 139 to the pump 62. Valves 63 and 64 are driven by a simple
on/off current waveform which has a Frequency
substantially equal to the frequency of the electrical signal driving pump 62,
but at a phase angle shifted from the frequency supplied
to the pump 62. In this manner, pump 62 and flow control valves 63 and 64 are
coordinated so as to work in concert for creating
the desired hydraulic pressure within hydraulic system 61. More specifically,
when flow control valves 63 and 64 are closed and
3 0 the elongation of the smart material of pump piston 71 begins, the stroke
of the piston 71 is reduced by its compliance as compression
stress increases and the resulting pump stroke is matched by hydraulic fluid
compression. Once the pressurization portion of the
total pump stroke is complete, outlet flow control valve 64 is directed by
controller 146 to open and the remaining stroke length
is used to pump out the pressurized liquid. At the end of this pump stroke,
valve 64 is directed to close before piston 71 begins
to retract. Since the entire pumping chamber 82 cannot be evacuated at the end
of the output stroke, the amount of remaining liquid
3 5 within chamber 82 expands once piston 71 retracts. After chamber 82 is
depressurized, inlet flow control valve 63 opens to admit
a new liquid charge. The amplitude of the electrical signal to coils 88 and 89
can be equal to or different than the amplitude of
the actuation signal to pump coil 72.
The waveform and timing of the electrical signals driving flow control valves
63 and 64 enables the valves to open and
close at the precise times corresponding to the optimized pressure and flow
needed to meet the output requirements of compact
4 0 actuator 21. The ability to precisely control the opening and closure of
valves 63 and 64 also permits actuator 21 to be operated
at the resonant frequency of pump 62. In addition, controller 146 can
synchronously open and close the flow control valves 63
_ _.~ .. _ _.... _ ~ ~ _ . ._._. .. . t , , . . .
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and 64 with the motion of piston 71 so that the valves open and close with
near zero pressure differential across them. Active
control valves 63 and 64 thus contribute to maximizing the efficiency of pump
62 and actuator 21.
The waveform shaping of active flow control valves 63 and 64 permits the
valves to open fast and close softly so as to
reduce valve seat wear. This is particularly important at higher frequencies.
The TERFENOL-D composition of valve pistons
86 and 87 permits relatively large displacements of the pistons over a wide
frequency range. Valves 63 and 64 open and close
at precise times corresponding to peak pump pressures, independent of the
system pressure. This precise electrical control of each
of the valves 63 and 64 enables suppression of pump ripple, present in most
hydraulic systems having passive valves therein, thus
removing the need for large ripple suppression equipment and integration with
load characteristics to suppress water hammer.
With each cycle of pump 62, a small volume of liquid is pumped through outlet
control valve 64 to servo valve 111. The
servo valve 111 alternatively directs the pressurized liquid from outlet
control valve 64 to the desired surface 46 or 47 of ram 41
so as to cause the ram to move in the desired direction relative to housing 31
and/or to change the relative pressure across head
42 and thus the external force being applied by ram 41. Controller 146
regulates servo valve 111 by means of motor 129. Unlike
the oscillating or poised signal provided by the controller 146 to pump 62 and
flow control valves 63 and 64, a constant current
is provided by controller 146 to motor 129 so as to cause actuation element
131 to elongate and move rod 121 to the position shown
in solid lines in FIG. 7. In the absence of such signal, rod 121 is in the
position shown in FIG. 5. As can be appreciated, ram
41 is moved to its extended position shown in FIG. 5 when pressurized liquid
is directed by servo valve 1 I I to first line 116. Ram
41 is retracted to its position shown in FIG. 7 when pressurized liquid is
directed by servo valve 111 to second line 117. Ram
4I can be stopped at any time between its extreme positions within chamber S6
by stopping the supply of electrical energy to pump
62 and closing one or both of flow control valves 63 and 64.
2 0 Differential pressure or displacement signals from transducers 161-163
provide an inner feedback control loop which allows
for a wide range of control schemes required by the multiple applications of
compact hydraulic actuator 21. Stroke transducer
163 provides a feedback signal to controller 146 indicating the position of
ram 41 within chamber 56. Pressure transducers 161
and 162 provide a feedback signal to the controller 146 indicating the
external force being applied on the ram 4I . These feedback
signals are incorporated into the control algorithm of the controller to
modify, if necessary, the signals provided by the controller
2 5 to pump 62, flow control valves 63 and 64 and servo valve 111.
The compact hydraulic actuator 21 of the present invention is a modular, self
contained linear motion device capable of
producing dynamic output strokes similar to those of conventional hydraulic
actuators yet at higher frequency and at significantly
reduced weight, complexity and volume. All of the components of unitized
actuator 21 are located inside hermetically sealed housing
31 so as to be protected from moisture and contamination. The integrated
package of actuator 21 ensures dynamic stability of
3 0 the components thereof and eliminates the need for multiple attachment
points. In contrast to conventional hydraulic approaches,
actuator 21 utilizes a high authority smart material such as TERFENOL-D. The
smart material motors for pump 62 and valves
63, 64 and 111 have no moving parts such as linkages, cams and the like. As
such, actuator 21 offers the advantages of reduced
cost, longer life, improved maintainability and increased reliability. The
compactness and integration of actuator 21 facilitates
its removal and replacement from wing 22 thus reducing installation and
maintenance costs.
3 5 Actuator 21 utilizes actuation members made from a magnetostrictive
material such as TERFENOL-D in pump 62, flow
control valves 63 and 64 and servo valve 111. The actuator 21 converts the
mechanical output of these smart material actuation
members, that is, high force, short stroke and high frequency, into a more
suitable output, that is, high force, long stroke and low
frequency, by locally generating and using hydraulic power. In this regard,
actuator 21 can produce any desirable output force
and stroke. The TERFENOL-D actuation elements of these components have a
response time ranging from ten microseconds to
4 0 ten seconds, preferably ranging from one to twenty milliseconds, and can
operate over a very broad frequency range (DC to ultrasonic)
without material or performance degradation. Pump 62 can thus operate at a
frequency up to 10 kHz.
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Pump 62 and flow control valves 63 and 64 can be configured by means of
controller 146 to provide pressure and flow
on demand. Unlike conventional hydraulic systems, actuator 2i is not
constantly absorbing power to keep the system under pressure
in order to react in time to a sudden demand. In position and hold
applications, there is also no need for constant power absorption.
As a result, actuator 21 can remain off for long periods of time before being
quickly actuated.
Pump 62 is relatively simple in comparison to conventional rotating pumps
having a multitude of moving parts. Pump
62 consists only of a diaphragm 76 driven directly by motor 69. This direct
drive of the diaphragm eliminates seal friction present
in conventional pump designs. Pump 62 in concert with flow control valve 63
and 64 is capable of generating pressures in excess
of 2,000 psi and, under certain configurations, in excess of 4,000 psi. More
specifically, pump 62 produces a pressure within
fluid system 61 ranging from 1 to 10,000 psi and preferably ranging from 2500
to 3500 psi and a flow rate ranging from 0 to 100
in'/minute and preferably ranging from 10 to 20 irt'lminute. The power
requirements of actuator 21 range from zero to 5000
watts and preferably from 100 to 200 watts. Preliminary calculations show that
before flow losses and without storage, an actuator
21 measuring 12"x9"x3" and weighing under 20 pounds can generate 1 GPM at 5000
psi pressure differential from S kVA rms
of 400 Hz ac line power. Size can be further reduced by increasing the output
pressure differential to around 8000 to 10,000 psi
and again by increasing operating frequency. The operating power level can be
reduced by providing enough internal pressurized
fluid storage to cover a duty cycle.
The current from controller 146 actuating coil I32 in servo valve 111 results
in effective positioning of spools 122 and
123 by the magnetostriction of actuation element 131. This direct positioning
of spools 122 and 123 by a drive current allows
for significantly higher bandwidths in servo valve 111 than can be achieved
with conventional solenoid-based servo valves.
Although the compact fluidic actuator of the present invention has been
described as being an hydraulic actuator, it should
2 0 be appreciated that the actuator can utilize pneumatics instead of
hydraulics and be within the scope of the present invention. In
addition, a compact actuator can be provided having one active flow control
valve of the type disclosed above and one passive
flow control valve. Alternatively, two passive flow control valves can be used
in place of active valves 63 and 64. A compact
actuator can also be provided having a pump andlor a servo valve which does
not include an active actuation element. Pump 62
can further include a stroke amplifier similar to amplifiers 91, 92 and 133
for amplifying the movement of piston 71. It should
2 5 be further appreciated that pump 62 and flow control valves 63 and 64,
each utilizing magnetostrictive or other smart material
actuation elements, can be produced as separate stand alone devices.
Actuator 21 is easily scalable for use in other applications. In addition,
actuator 21 is easily reshaped and reconfigured
to suit the particular application. Further aeronautics applications include
helicopter rotor blade noise and vibration control and
steering and brake actuation systems. Other exemplary applications include
process control applications that are remote operating,
3 0 such as well head control, gauge stations and pipeline valves that only
have electric power available for operation. These control
valves can be remotely activated by means of an electric signal with the self
contained actuation apparatus herein, which provides
as advantages improved control and reduced size. The actuators herein are
useful for well applications such as submersible pumps
for oil and water and downhole drill bit operation and seismic sources. They
are also useful for micropositioning applications
such as precision drug delivery and ink control on computer printers where
accurate metering and delivery is required. Automotive
3 5 applications include hydraulic clutches, hydraulic clamps, hydraulic or
pneumatic brakes, power steering pumps, fuel injection,
brake, suspension and steering systems. Since the actuators of the present
invention have little vibration and thus a low acoustic
signature, they are well suited for use in submarines for replacing
conventional hydraulic systems. Applications further include
any other industrial application in which a distributed control algorithm in
lieu of a centralized hydraulic source and master cylinder
architecture is utilized.
4 0 It should be appreciated that the flow control valves of actuator 21 can
have other configurations or embodiments. For
example, in FIG. 8 there is shown a fragmentary view of actuator 21 having
therein a normally open flow control valve 171
substantially similar to inlet control valve 63 and outlet control valve 64
described above. Like reference numerals have been used
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in FIG. 8 to describe like components between valve 171 and valves 63 and 64.
As shown in FIG. 8, flow control valve 171 is
disposed inside housing 31 and has a motor 172 substantially identical to
motors 83 and 84. Motor 172 has an electrical connector
I73 for electrically coupling the motor to controller 146. An amplifier 176 is
included within valve 171 for amplifying the stroke
of the smart material actuation element or piston of motor 172. Stroke
amplifier 176, not cross sectioned in the drawings, is of
a conventional type and substantially similar to stroke amplifiers 91, 92 and
133. The amplifier has an output rod 177 slidably
carried therein and movable longitudinally as a function of the longitudinal
movement of the piston within motor 172.
Flow control valve 171 has a poppet valve 178 which includes an elongate
cylindrical valve stem 181. The stem 181 extends
through a plug 182 disposed within a bore 183 provided in actuator housing 31.
Fluid system 61 of actuator 21 has a first or inlet
passageway portion 186 and a second or outlet passageway portion 187 which
communicate with each other by means of poppet
valve 178. Valve stem 181 extends across outlet passageway portion 187. A
conventional seal 191 made from any suitable material
such as a compliant polymer material is carried by the plug 182. Seal 191 is
concentrically mounted about valve stem 181 for
inhibiting the flow of fluid through plug 182. A valve plug 192 is mounted to
the end of the valve stem 181. Valve stem and plug
181 and 192 are each made from any suitable noncorrosive material such as a
stainless steel alloy or a polymer material. Plug
192 is sized and shaped to sealably engage a valve seat 193 secured within a
bore 196 extending between passageway portions
186 and 187. Valve seat 193 has an orifice 197 which permits the Liquid within
fluid system 61 to flow from inlet passageway
portion 186 to outlet passageway portion 187.
In operation and use, normally open flow control valve 171 permits the liquid
within fluid system 61 to flow through orifice
197 in the absence of power to motor 172. Valve stem and plug 181 and 192 are
movable from their first or open positions, shown
in FIG. 8, to second or closed positions (not shown) upon actuation of motor
172. In the closed positions, valve plug 192 engages
2 0 valve seat 193 to close off orifice 197 and thus preclude fluid from
flowing between passageway portions 186 and 187. Stroke
amplifier 176 provides the necessary longitudinal movement of valve stem 181,
without the need for increasing the size of the piston
in motor 172, for operation of poppet valve 178. Stroke amplitier 176 may be
particularly preferred in a two-stage valve.
In FIG. 9, a normally closed flow control valve 204 is shown. Valve 204 is
substantially similar to valve 171 and thus
like reference numerals have been used in FIG. 9 to identify like components
in valves 204 and 171. Flow control valve 204 has
2 5 a poppet valve 206 which includes a valve seat 207 made from the same
material as valve seat 193 and disposed within bore 196.
Poppet valve 206 further includes an elongate valve stem 208 substantially
similar to valve stem 18i. Valve seat and stem 207
and 208 are made from the same materials as valve seat and stem 193 and 181.
Valve seat 207 is provided with an orifice 209
sized and shaped to permit valve stem 208 to extend therethrough. A valve plug
212, made from the same material as valve plug
192, is secured to the end of valve stem 208 and is disposed within outlet
passageway portion 187. A further bore 213 is provided
3 0 in housing 31 and is longitudinally aligned with bores 196 and 183 to
permit access to the poppet valve 206 and plug 182. A cap
214 is sealably disposed and secured within bore 213.
In operation and use, flow control valve 204 is in its normally closed
position shown in FIG. 9 when motor 172 is not being
energized. As such, the liquid of fluid system 61 is precluded from traveling
through passageway portions 186 and 187 of the
valve 204. Upon actuation of motor 172, valve plug 212 disengages from seat
207 and moves into inlet passageway portion 186
3 5 to permit liquid to flow through orifice 209 provided in the valve seat
207.
In a further embodiment of the integrated electric actuator of the present
invention, a schematic of a compact actuator 221
is shown in FIG. 10 which is substantially identical to compact actuator 21.
Like reference numerals have been used in FIG. 10
to describe the like components of actuators 221 and 2I . Pump 62 of compact
actuator 221 is bi-directional in comparison to uni-
directior>al pump 62 of compact actuator 21. Flow control valves 63 and 64 of
actuator 221 can alternatively serve as inlet valve
4 0 or outlet valves to pump 62. First flow control valve 63 is fluidly
connected to first line 116 and second flow control valve 64
is fluidly connected to second line 117. Controller 146 is programmed to cause
the bi-directional flow control valves 63 and 64
to alternatively move the liquid within fluid system 61 in a first direction
through a pump 62, in which the liquid flows out of second
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flow control valve 64 to second portion 56b of ram chamber 56, or in a second
direction opposite of the first direction, in which
the liquid flaws out of first flow control valve 63 to first portion 56a of
the ram chamber.
The bi-directionality of pump 62 eliminates the need for servo valve 111 in
compact actuator 221. In place of high pressure
accumulator 138 or a low pressure reservoir I39, actuator 221 has a single
hydraulic tank 222 coupled to first and second lines
116 and 117 by means of respective lines 226 and 227. Tank 222 is vented,
however a low-pressure gas or spring accumulator
could also be used. Conventional poppet valves 228 and 229 regulate the flow
of liquid between lines 112 and 113 and the hydraulic
tank 222 and allow the tank 222 to provide liquid, as needed, to the low
pressure side of fluid system 61 and isolate the tank from
the high pressure side of the system 61.
Controller 146 synchronizes the drive currents to pump 62 and first and second
flow control valves 63 and 64 to achieve
pumping in either direction within fluid system 61. FIG. 12 shoes time
histories for the synchronized input signals to pump 62
and valves 63 and 64 for pumping liquid out second valve 64. A sinusoidal
current is shown driving pump 62, although other
periodic wave forms can be used in the alternative. The output rate of pump 62
is preferably controlted by modulating the amplitude
of the input wave form. Alternatively, frequency control of the input wave
form to pump 62 can also be used for determining
the output rate of the pump. The time history for the position of pump piston
71 is similar to the input wave form for the pump,
varying slightly due to the non-linear nature of the magnetostrictive material
of piston 71 and the drive load exerted on the piston
71.
The second and third time histories shown in FIG. 12 are for the first and
second check valves 63 and 64. As seen, the
input signals for each of the valves 63 and 64 is similar to a square wave,
except that the current ramps upwardly to and downwardly
from the maximum current. First check valve 63 is acting as the input check
valve and opens during the downward stroke of pump
2 0 62 so as to allow liquid to be drawn into pumping chamber 82. The first
check valve 63 closes just as pump piston 71 reaches
its minimum position, in which pumping chamber 82 has maximum volume. Second
check valve 64 is acting as the output check
valve in the synchronization shown in FIG. 12, and opens during the upward,
pressurizing motion of pump piston 71. Second
check valve 64 closes as the pump stroke reaches its maximum value, in which
pumping chamber 82 has minimum volume.
To reverse the direction of liquid through pump 62, the synchronization of the
input current to first and second check valves
2 5 63 and 64 is reversed so that second check valve 64 becomes the inlet
check valve and first check valve 63 becomes the output
check valve.
Controller I46 directs ram 41 to move to an extended position by causing pump
62 to move the liquid of fluid system 61
through first flow control valve 63 and fine 116. The liquid enters first
chamber portion 56a and engages upper surface 46 of ram
head 42 to thus cause threaded end 43 of the ram 41 to extend outwardly from
housing 31. When it is desired to retract rod 43
3 0 relative to housing 31, controller 146 resynchronizes the signals to check
valve motors 83 and 84. Liquid within fluid system 61
now flows from second flow control valve 64 into second line 117 and then
second chamber portion 56b to increase the hydraulic
pressure upon lower surface 47. The closed looped fluid system 61 is
simultaneously moving liquid from first chamber portion
56a so as to reduce the hydraulic pressure on upper surface 46 of ram head 42.
In this manner, the redistribution of pressure across
head 42 causes rod 43 to retract relative to housing 31.
3 5 The schematic of FIG. 11 includes a flow chart depicting the operation of
controller 146. The inputs to controller 146
include the commanded position signal 231 for ram 41, the measured position
for the ram 41 obtained by position sensor 163 and
the measured differential pressure across ram 41 obtained by first and second
pressure sensors 161 and 162. Controller 146 compares
the commanded position signal 231 to the measured position signal in position
comparison step 236 to form a position error signal
237 which is the difference between the commanded and the measured position of
the ram 41. The position error signal 237 is
4 0 used as an input to a position controller 238 which includes a control
filter or algorithm that implements a differential equation
in calculation step to determine the commanded force signs! 241 required to
drive ram 41 to the commanded position. The algorithm
utilized in calculation step within position controller 238 accounts for the
stability requirements of the system in which compact
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actuator 221 is utilized, uncertainties and variations in the actuator 221,
desired closed-loop accuracy and dynamic range and any
noise within sensors 161-163.
The commanded force signal 241 is passed through a pressure estimator 242,
which in a pressure estimation step derives
a commanded pressure signal 243. The pressure estimator is, in general, a
dynamic signal processing element which, in its simplest
form, divides the commanded force signal 241 by the hydraulic actuator area to
determine the commanded pressure signal 243.
In pressure comparison step 246, a pressure difference error signal 247 is
determined from a comparison of the commanded
pressure signal 243 to the differential pressure on upper and lower surfaces
46 and 47 of ram head 42 as measured by first and
second pressure sensors 161 and 162. The measured pressures from sensors 161
and 162 are differenced to provide the differential
pressure acting on piston head 42. The pressure difference error signal 247 is
used as the input to pressure controller and pump
and check valve drive electronics 248. The pressure difference error signal
247 has both sign and magnitude so as to indicate to
pressure controller or filter 248 both the amount of desired pressure that
pump 62 must produce and which output of the pump
should be at higher pressure.
The signal flow portions of controller 146 are implemented by any suitable
means such as one or more microcontrollers
or digital signal processing hardware/software. The drive currents are
produced by any suitable means such as power semiconductor
1 5 technologies.
The bi-directional operation of pump 62 permits compact actuator 221 to be
relatively smaller, simpler and less expensive
than compact actuator 21. The direction of liquid through pump 62 is changed
by merely changing the phasing of the electrical
signals to flow control valves 63 and 64. Pump 62 requires no operating point
adjustment.
The inclusion of first and second pressure sensors 161 and 162 provides a
closed loop pressure control system in compact
2 0 actuator 221 which allows more accurate control of the power delivered to
the hydraulic load. This closed loop pressure control
system compensates for the influence of operation conditions such as
temperature, wear and hydraulic load variations by delivering
controlled pressure to the hydraulic load in the presence of these variations.
This system allows controller 146 to deliver power
only when required to maintain desired pressure levels, thus increasing the
efficiency of actuator 221.
The closed loop or pressure control system described above can be used to
provide force control of the output at ram 41
2 5 of the hydraulic system of compact actuator 221. The force, and even
torque, output of the hydraulic system can be regulated
by controlling by means of controller 146, as described above, the input
pressure to ram 41 from the feedback signals of sensors
161-162.
The inclusion of position sensor 163 with the closed loop pressure control
system described above provides a closed loop
motion control system in compact actuator 221. In such a system, the inner
pressure or force loop derived from pressure sensors
3 0 161-162 and lines 166, shown in FIG. 11, is controlled by an outer
position loop derived from position sensor 163 and the related
line 166. The use of these two loops to provide position control allows the
outer position loop to be designed without detailed
knowledge of the generally nonlinear dynamics of compact actuator 221. The
high bandwidth of the inner force loop shields the
outer position loop from these undesirable dynamics. Actuator 221 so
configured as a motion controller can be specialized to the
case where feed-forward information about the desired motion profile is
available.
3 5 It should be appreciated that an integrated electric actuator of the
present invention can be provided having only closed
loop pressure control, that is no position sensor 163 for providing motion
control, or alternatively open loop control, that is no
sensors 161-163 for providing pressure and motion control. In an open loop
configuration, the simplified controller 146 has as
input electrical power and a desired pump output flow rate. Other
implementations of the integrated electric actuator herein can
be provided having a controller which provides a voltage modulated control
signal to pump 62 and first and second flow control
4 0 valves 63 and 64, instead of a current modulated control signal as
described above.
It should be appreciated that the pump and valve apparatus of compact
actuators 21 and 221 can have other configurations
or embodiments. In FIG. 13, for example, a pump and valve apparatus 301 having
inlet and outlet passive, spring-loaded check
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valves is provided in a housing 302 substantially similar to housing 31. A
portion of actuator housing 302 is shown in FIG. 13.
An elongate cylindrical cavity or pumping chamber 303 extending along a
longitudinal axis 304 is provided in housing 302. Pumping
chamber 303 is formed from an inner cylindrical surface 306 and a generally
planar end surface 307 extending perpendicularly
to cylindrical surface 306. A cylindrical piston member or piston 311 is
disposed in pumping chamber 303. Housing 302 and
piston 311 are each made from any suitable material such as stainless steel.
Piston 311 has an outer cylindrical surface 312 and
a planar end surface 313 extending at a right angle to outer cylindrical 312.
The diameter of the outer cylindrical surface 312 is
slightly smaller than the diameter of inner cylindrical surface 306. Piston
311 is slidable along longitudinal axis 304 between a
first position in which end surface 313 is in close proximity to end surface
307, shown in solid lines in FIG. 13, and a second position
in which the insert 313 is spaced farther away from end surface 307, shown in
phantom lines in FIG. 13.
Pump and valve apparatus 301 includes means in the form of a transducer or
motor 316 for driving piston 311 between
its first and second longitudinal positions within pumping chamber 303. Motor
316 has a cylindrical rod-like element in the form
of actuation element 317 made from any suitable active or smart material which
changes shape when energized by being placed
in an electromagnetic field. Preferred materials for actuation element 317 are
the magnetostrictive materials discussed above with
respect to rod 71 and more preferably a giant magnetostrictive material such
as TERFENOL-D. A drive coil 318 substantially
similar to coil 72 is concentrically carried or disposed about actuation
element 317 and serves as means for creating an electromagnetic
field through at least a portion of actuation element 317. More specitically,
drive coil 318 creates an electromagnetic field through
the entire actuation element 317. The actuation element 317 elongates when in
the presence of such a magnetic field. An amplifier
321 is included within motor 316 for amplifying the stroke of actuation
element 317. Stroke amplifier 321, not cross sectioned
in FIG. 13, is of a conventional type and is substantially similar to stroke
amplifiers 91 and 92. The amplifier 321 has an output
2 0 rod 322 slidably carried therein and movable longitudinally as a function
of the longitudinal movement of actuation element 317.
The output rod 322 has an end secured to piston 311 by any suitable means such
as a weld (not shown). Means for prestressing
and/or magnetically biasing the magnetostrictive material of actuation element
317 can be included within motor 316 and be within
the scope of the present invention.
A first or inlet poppet valve 331 is provided in piston 311 for controlling
the flow of liquid from inlet line 112 into pumping
2 5 chamber 303. In this regard, a cylindrical valve chamber 332 extends
through end surface 313 along longitudinal axis 304 and
terminates at a valve seat 333 formed in the piston 311. A fluid passageway
334 extends longitudinally through valve seat 333
and then transversely through piston 31 I and outer cylindrical surface 3I2
thereof. Inlet line 312 extends through inner cylindrical
surface 306 to communicate with fluid passageway 333. In this regard, a
channel 336 extends longitudinally from fluid passageway
333 along outer cylindrical surface 312 toward piston end surface 313 for
permitting communication between the fluid passageway
3 0 333 and inlet line 112 throughout the slidable movement of piston 311 in
pumping chamber 303.
A valve head in the form of ball 337 is disposed in valve chamber 332 for
engaging valve seat 333 and inhibiting the flow
of liquid from fluid passageway 334 into valve chamber 332. Ball 337 is
movable along longitudinal axis 304 within valve chamber
332 between a first or closed position in engagement with valves 333, shown in
solid lines in FIG. i3, and a second or open position
spaced longitudinally from valve seat 333, shown in phantom lines in FIG. i3.
Inlet valve 331 has means which includes helical
3 5 spring 341 for urging ball 337 to its closed position within the valve
seat 333. Spring 341 is longitudinally disposed within valve
chamber 332 and has one end engaging ball 337 and a second opposite end
engaging a tubular retainer 342 press fit or otherwise
suitably secured within chamber 332 flush with piston end surface 313. The
tubular retainer 342 is provided with a bore 343 extending
longitudinally therethrough for permitting liquid to pass from valve chamber
332 through end surface 313 into pumping chamber
303. Ball 337, spring 341 and retainer 342 are each made from any suitable
material such as stainless steel.
4 0 Means is carried by housing 302 and piston 311 for precluding rotation of
the piston 311 about longitudinal axis 304 within
pumping chamber 303. Said means includes a longitudinally extending spline 346
extending radially inwardly from a cylindrical
surface 306 into a longitudinal groove 347 provided in outer cylindrical
surface 312 of piston 311. The interengagement of spline
.~_.__. _..,r...___._.._"... _.._....... . .r , .... . ~ . _ .........._ .
......
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346 and groove 347 serves to retain channel 336 and fluid passageway 334 in
communication with inlet line 112 throughout the
longitudinal movement of piston 311 within pumping chamber 303.
Annular sealing means in the form of first and second longitudinally spaced-
apart O-rings 351 and 352 are carried by piston
311 for precluding liquid passing from inlet line 112 into fluid passageway
334 from flowing around the ends of piston 311. O-rings
351 and 352 are disposed within respective first and second annular grooves
353 and 354 extending circumferentially around outer
cylindrical surface 312 of piston 311.
A second or exhaust valve 361 is provided within housing 302 for permitting
liquid to flow out of pumping chamber 303
into outlet line 313. Exhaust or outlet poppet valve 361 is substantially
similar to inlet valve 331 and includes a longitudinally-
extending valve chamber 362 formed with a valve seat 363 at one end thereof. A
fluid passageway 364 extends longitudinally
through valve seat 363 and end surface 307 for permitting communication
between valve chamber 362 and pumping chamber 303.
A ball 366 is disposed in valve chamber 362 for longitudinal movement therein
between a closed position in engagement with valve
seat 363 and an open position spaced apart from the valve seat 363. A helical
spring 367 serves to retain ball 366 within valve
chamber 362 and urge the ball against valve seat 363. Helical spring 367 is
retained in place by a tubular retainer 368 secured
within valve chamber 362 and provided with a bore extending longitudinally
therethrough for permitting fluid communication between
the valve chamber 362 and outlet valve 113. Ball 366, spring 367 and retainer
368 are substantially similar to ball 337, spring
341 and retainer 342 described above.
In operation and use, inlet valve 331 controls the flow of liquid from inlet
line 112 into pumping chamber 303 and exhaust
valve 361 controls the flow of the pressurized fluid from the pumping chamber
into outlet line 113. Ball 337 unseats from valve
seat 333 when the pressure in inlet line 112 exceeds the pressure in pumping
chamber 303. Similarly, ball 366 of exhaust valve
2 0 361 unseats from valve seat 363 when the pressure within pumping chamber
303 exceeds the pressure in outlet line 113.
The incorporation of inlet valve 331 within piston 311 increases the
efficiency of pump and valve apparatus 301. Specifically,
the longitudinal movement of ball 337 in valve chamber 332 is aligned and in
the same direction with the longitudinal movement
of piston 311 in pumping chamber 303 so that the longitudinal motion of piston
assists in unseating and seating ball 337 with respect
to valve seat 333. For example, when piston 311 is changing its direction from
its downward stroke to its upward stroke in FIG.
2 5 13, the downward momentum of ball 337 and the liquid within both valve
chamber 332 and fluid passageway 334 assists in unseating
the ball 337 from valve seat 333. The stiffness of spring 341 can thus be
increased without increasing the differential fluid pressure
required to open inlet valve 331. In addition, the time required to open valve
331 is decreased. As such, the motion of piston
311 enhances the operation of valve 331 and increases the allowable operating
frequency of pump and valve apparatus 301. The
efficiency of pump and valve apparatus 301 is particularly enhanced when
operated at its resonant frequency. Since the operating
3 0 frequency of pump and valve apparatus 301 correlates directly with the
flow rate, increased flow rates are provided.
Although motor 316 is shown with a stroke amplifier 321, it should be
appreciated that a motor having an actuation element
317 and drive coil 318 can be provided without a stroke amplifier and be
within the scope of the present invention. Furthermore,
it should be appreciated that other types of motors or means for moving piston
longitudinally within pumping chamber 303 can
be utilized.
3 5 In an alternate embodiment of pump and valve apparatus 301, an annular
groove can be provided around piston 311 in
place of channel 336 to ensure continued fluid communication between fluid
passageway 333 and inlet line 112 throughout the
stroke of the piston. The annular groove would be disposed between O-rings 351
and 352 and would have a length and depth similar
to the length and depth of channel 336. Such an annular groove would eliminate
the need for spline 346 and groove 347.
Another embodiment of the pump and valve apparatus of the present invention is
shown in FIG. 14. Pump and valve apparatus
4 0 381 therein is substantially similar to pump and valve apparatus 301 and
like reference numerals have been used to describe like
components of apparatus 301 and 381. Inlet valve 331 is longitudinally
centered on a longitudinal axis 382 spaced-apart from and
aligned parallel to central longitudinal axis 304.
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Second or exhaust valve 386 is incorporated in piston 311 and extends along
another longitudinal axis 387 spaced-apart
and parallel to both axes 382 and 304. Exhaust valve includes a cylindrical
valve chamber 388 which opens onto end surface 313
of piston 311. An annular shoulder 391 forms the terminus of valve chamber 388
within piston 311. A fluid passageway 392
has a longitudinal portion which opens into valve chamber 388 at shoulder 391
and a transverse portion which extends through
outer cylindrical surface 312 of piston 311. Outlet line 113 opens into inner
cylindrical surface 306 of pumping chamber 303 to
communicate with fluid passageway 392. A channel 393, substantially similar to
channel 336, extends longitudinally from fluid
passageway 392 toward piston end surface 313 for permitting communication
between the fluid passageway 392 and the outlet
line 113 throughout the longitudinal movement of piston 31 I within pumping
chamber 303. A tubular member or retainer 396
is press fit or otherwise suitably secured within valve chamber 388 adjacent
piston end surface 313. A bore 397 extends through
tubular member 396 to a valve seat 398 formed by the inner end of tubular
member 396. Ball 406 and helical spring 407 are disposed
in valve chamber 388. Ball 406 is movable between a first position in
engagement with valve seat 398 and a second position spaced
apart from the valve seat. Helical spring 407 abuts shoulder 391 at one end
and engages ball 406 at the other end for urging the
ball against valve seat 398. Ball 406, spring 407 and retainer 396 are
substantially similar to ball 337, spring 341 and retainer
342 described above. Third O-ring 411 disposed within third groove 412
extending circumferentially around the piston 311 serves
as annular seal means between channel 393 and piston end surface 313. Thus,
liquid traveling between fluid passageway 392 and
outlet line I13 is bound between second and third O-rings 352 and 411.
The operation and use of pump and valve apparatus 381, and specifically inlet
valve 331 thereof, is substantially similar
to the operation of pump and valve apparatus 301. Incorporation of exhaust
valve 386 into piston 311 further enhances the operating
efficiency of pump and valve apparatus 381. Exhaust valve 386 operates in
substantially the same manner as inlet valve 331.
2 0 In this regard, when piston 311 changes directions between its upward
stroke and its downward stroke in FIG. 14, the change in
momentum of ball 406 and the liquid in valve chamber 388 and bore 397 provide
an additional force for unseating ball 406 from
valve seat 398.
Active valves can be substituted for the passive poppet valves of pump and
valve apparatus 301 and 381. Pump and valve
apparatus 421 illustrated in FIG. 15 is similar in certain respects to pump
and valve apparatus 30I and 381 and like reference numerals
2 5 have been used to describe tike components of apparatus 301, 361 and 421.
Pump and valve apparatus 421, shown somewhat
schematically in FIG. 15, is formed from a pump housing 422 having a removable
end cap 423. Pump housing 422 and end cap
423 are each made from any suitable material such as stainless steel and are
part of housing 302 described above. Pump housing
422 is provided with a cylindrical pumping chamber 426 extending along a
central longitudinal axis 427. Chamber 426 is formed
in part by an inner cylindrical surface 428. End cap 423 has a cylindrical
portion 431 formed with an outer cylindrical surface
3 0 432 and a planar end surface 433 extending at a right angle to cylindrical
surface 432. Cylindrical portion 431 is disposed in housing
422 and secured to the pump housing by any suitable means so that end surface
433 forms one end of pumping chamber 426. Annular
seal means in the form of an O-ring 436 disposed within an annular groove 437
provided in outer cylindrical surface 432 provides
a fluid-tight seal between the outer and inner cylindrical surfaces 432 and
428.
A cylindrical piston 441 substantially similar to piston 311 described above
and having an outer cylindrical surface 442
3 5 and a planar end surface 432 extending perpendicularly to outer surface
442 is disposed within pumping chamber 426. Piston 441
is longitudinally movable by motor 3I6 from a first position where end surface
443 thereof is in close proximity to end surface
433 and a second position in which piston end surface 443 is moved away from
end surface 433. First and second O-rings 451
and 452 disposed within respective first and second annular grooves 453 and
454 provided in outer cylindrical surface 442 provide
a fluid-tight seal between piston 441 and inner cylindrical surface 428 of
pump housing 422.
4 0 A first or inlet valve 456 is provided in cylindrical portion 431 for
controlling the flow of liquid from inlet line 112 into
pumping chamber 426. Inlet valve 456 is aligned along longitudinal axis 427
and includes a longitudinally-extending valve chamber
458 extending through end surface 433 to a valve seat 459 formed within
cylindrical portion 431. A first fluid passageway 461
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is provided in valve seat 459 and cylindrical portion 431 for communicating
with inlet line 112. A second fluid passageway 462
extends between the inner cylindrical surface of valve chamber 458 and outer
cylindrical surface 432 of cylindrical portion 431
where it opens into a channel 463 provided in surface 432. Channel 463 extends
longitudinally through end surface 433.
A valve head 466 made from steel or any other suitable material is disposed
within valve chamber 458 for longitudinal
movement and cooperative engagement with valve seat 459. Means for moving
valve head 466 between opened and closed positions
relative to valve seat 459 includes a motor 467 substantially similar to motor
83 and having an active drive element or piston 471
energized by a coil 472 concentrically carried thereabout. Piston 471 can be
made from any of the materials discussed above with
respect to piston 71, and is preferably made from a giant magttetostrictive
material such as TERFENOL-D. Motor 467 is diametrically
sized smaller than valve chamber 458 so that liquid passing through valve seat
459 travels between motor 467 and the inner surface
of valve chamber 458 to second fluid passageway 462. Motor 467 is mounted on a
cylindrical plug 473 made from stainless steel
or any other suitable material. Plug 473 is secured within the end of valve
chamber 458 flush with end surface 433 by any suitable
means. A stroke amplifier and means for prestressing andlor magnetically
biasing the magnetostrictive material of piston 471
can be included within motor 467 and be within the scope of the present
invention.
A second or exhaust valve 481 is longitudinally disposed within piston 441.
Exhaust valve 481 has a valve chamber 482
which extends longitudinally through piston end surface 443. Valve chamber 482
is longitudinally aligned with valve chamber
458. A tubular member or retainer 483 made from stainless steel or any other
suitable material is secured within valve chamber
482 flush with end surface 443. The inner end of tubular retainer 483 is
formed as a valve seat 486. A central bore 487 extends
longitudinally through valve seat 486 and tubular retainer 483. A valve head
491 made from steel or any other suitable material
is provided for sealable engagement with valve seat 486.
2 0 Means for moving valve head 491 from a first or closed position in
engagement with valve seat 486 and a second or open
position spaced away from valve seat 486 includes a motor 492 substantially
identical to motor 467. Motor 492 has a cylindrical
piston 493 and a coil 494 concentrically disposed about piston 493. Piston 493
is in its de-energized state and valve head 491 in
an open position in FIG. 15. Motor 492 is mounted to the end surface of valve
chamber 482 formed by piston 471. Cylindrical
motor 492 has an external diameter less than the internal diameter of valve
chamber 482 so as to permit liquid passing through
2 5 valve seat 486 to flow through valve chamber 482 between motor 492 and the
inner cylindrical surface of piston 471 to a fluid
passageway 496 extending radially between valve chamber 482 and outer
cylindrical surface 442. A longitudinally-extending channel
497 provided in outer cylindrical surface 442 between first and second O-rings
451 and 452 opens into fluid passageway 496.
Outlet line 113 extends through inner cylindrical surface 428 for
communication with fluid passageway 496 or channel 497 throughout
the longitudinal movement of piston 441 for the egress of liquid from pumping
chamber 426.
3 0 Means (not shown) similar to spline 346 and groove 347 are carried by pump
housing 422 and piston 441 for precluding
rotational movement of piston 441 about central longitudinal axis 427 for thus
ensuring the registration of fluid passageway 496
and channel 497 with outlet line 113.
Pump and valve apparatus 421 operates in substantially the same manner as
described above with respect to pump and valve
apparatus 301 and 381. When energized by controller 146, motors 467 and 492
serve to close respective inlet and exhaust valves
3 5 456 at appropriate times and for appropriate durations for the operation
of pump and valve apparatus 421. The operating efficiency
of exhaust valve 481 is enhanced by its disposition within piston 441. As
discussed above, the change in momentum of valve head
491 and the liquid within bore 487 and valve chamber 482 provide an additional
force for opening valve head 491 when piston
441 changes direction from moving upwardly in FIG. 15 to moving downwardly.
Although pump and valve apparatus 421 is shown as having only exhaust valve
481 disposed within piston 441, it should
4 0 be appreciated that one or both of inlet and exhaust valves 456 and 481
can be provided in piston 441 and be within the scope of
the present invention.
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The integrated electric actuator herein can have means for prestressing and/or
magnetically biasing the magnetostrictive
drive element, as described in copending U.S. patent application Serial No.
081855,228 filed May 13, 1997 (File No. A-64718)
incorporated herein by this reference, and be within the scope of the present
invention. In addition, and as also described in U.S.
patent application Serial No. 081855,228 filed May 13, 1997 (File No. A-
64718), ac magnetic flux return means can be provided
in the actuator of the present invention.
From the foregoing, it can be seen that a new and improved fluidic actuator
has been provided. The fluidic or integrated
electric actuator is relatively compact in size and is easily scalable for
different applications. The actuator provides hydraulic power
with little acoustic noise. It has relatively few moving parts and uses
electricity as a power source. A self-contained fluid system
having a relatively small volume of fluid is utilized in the actuator. An
output of relatively long stroke and high force is provided
by the actuator. The actuator utilizes motors having smart material actuation
elements made from TERFENOL-D. A method
for operating the actuator is provided. The actuator can have a pumping
apparatus which utilizes the momentum of the pump piston
to enhance the efficiency of inlet andlor exhaust valves of the pump.
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