Abstract:
An actuator includes a pump including a first cavity and a diaphragm coupled in flow communication with the first cavity. The diaphragm is configured to pressurize a fluid contained in the first cavity. The pump further includes a first valve coupled in flow communication with the first cavity. The first valve is configured to release fluid from the first cavity when the first cavity is pressurized. The actuator also includes a piston assembly operatively coupled to the pump.

Description:
BACKGROUND 
       [0001]    The field of the disclosure relates generally to gas turbine engines and, more particularly, to a system for actuating movable components of gas turbine engines using piston driven actuators. 
         [0002]    Gas turbine engines typically include one or more movable components such as variable stator vanes (VSVs) and variable bleed valve (VBV) doors. In known gas turbine engines, VSVs and VBV doors are movable as a set using piston-based actuators driven with dedicated hydraulic lines. In such known gas turbine engine piston-based actuators, because of weight and space considerations, dedicated hydraulic lines represent a substantial burden on improved engine performance, including in terms of specific fuel consumption (SFC). Further, the dedicated hydraulic lines in such known piston-based actuators require a number of dedicated control systems and take up a substantial amount of space. 
         [0003]    Furthermore, such known gas turbines utilizing known hydraulically actuated piston-based actuators are unable to effectively actuate VSVs and VBV doors individually. Rather, due to space and weight constraints, VSVs and VBV doors are actuated more than one individual component at a time in a set. As such, such known piston-based actuators are unable to effect independent modulation of VSV stages and VBV doors to accomplish, for example, active stall control for higher pressure ratios. Moreover, utilizing known hydraulically actuated piston-based actuators is limited in the displacement of VSVs and VBV doors, and therefore place limits on performance of such known gas turbine engines including advanced compressor designs and high speed boosters that are required for active stall control. 
       BRIEF DESCRIPTION 
       [0004]    In one aspect, an actuator is provided. The actuator includes a pump including a first cavity and a diaphragm coupled in flow communication with the first cavity. The diaphragm is configured to pressurize a fluid contained in the first cavity. The pump further includes a first valve coupled in flow communication with the first cavity. The first valve is configured to release fluid from the first cavity when the first cavity is pressurized. The actuator also includes a piston assembly operatively coupled to the pump. 
         [0005]    In another aspect, an actuation system for a gas turbine engine is provided. The gas turbine engine includes at least one movable component and at least one immovable component. The actuation system includes at least one actuator that includes a pump. The pump includes a first cavity and a diaphragm coupled in flow communication with the first cavity. The diaphragm is configured to pressurize a fluid contained in the first cavity. The pump further includes a first valve coupled in flow communication with the first cavity. The first valve is configured to release fluid from the first cavity when the first cavity is pressurized. The at least one actuator also includes a piston assembly operatively coupled to the pump. The at least one actuator is coupled to and between the at least one movable component and the at least one immovable component. The at least one actuator is configured to facilitate alternating movement of the at least one movable component relative to the at least one immovable component. 
         [0006]    In yet another aspect, a gas turbine engine is provided. The gas turbine engine includes at least one movable component, at least one immovable component, and at least one actuator. The at least one actuator includes a pump that includes a first cavity and a diaphragm coupled in flow communication with the first cavity. The diaphragm is configured to pressurize a fluid contained in the first cavity. The pump further includes a first valve coupled in flow communication with the first cavity. The first valve is configured to release fluid from the first cavity when the first cavity is pressurized. The at least one actuator also includes a piston assembly operatively coupled to the pump. The at least one actuator is coupled to and between the at least one movable component and the at least one immovable component. The at least one actuator is configured to facilitate alternating movement of the at least one movable component relative to the at least one immovable component. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    These and other features, aspects, and advantages of the present disclosure will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein: 
           [0008]      FIGS. 1-8  show example embodiments of the apparatus and method described herein. 
           [0009]      FIG. 1  is a schematic illustration of an exemplary gas turbine engine. 
           [0010]      FIG. 2  is a schematic illustration of a portion of an exemplary high pressure compressor (HPC) that may be used in the gas turbine engine shown in  FIG. 1 . 
           [0011]      FIG. 3  is a perspective and cross-sectional schematic diagram of a portion of the exemplary HPC shown in  FIG. 2 . 
           [0012]      FIG. 4  is an aft-to-forward perspective view of an exemplary actuation system utilizing micro-electromechanical systems (MEMS) that may be used in the HPC shown in  FIGS. 2 and 3 . 
           [0013]      FIG. 5  is a forward-to-aft perspective and cross-sectional schematic diagram of an exemplary fan frame which may be used in the gas turbine engine shown in  FIG. 1 . 
           [0014]      FIG. 6  is a forward-to-aft perspective and sectional view of an exemplary actuation system utilizing MEMS which may be used in the fan frame shown in  FIG. 5 . 
           [0015]      FIG. 7  is a cross-sectional view of an exemplary embodiment of a MEMS actuator assembly which may be used in the gas turbine engine shown in  FIG. 1 . 
           [0016]      FIG. 8  is a schematic view of an exemplary control scheme which may be used with the MEMS actuator assembly shown in  FIG. 7 . 
       
    
    
       [0017]    Although specific features of various embodiments may be shown in some drawings and not in others, this is for convenience only. Any feature of any drawing may be referenced and/or claimed in combination with any feature of any other drawing. 
         [0018]    Unless otherwise indicated, the drawings provided herein are meant to illustrate features of embodiments of the disclosure. These features are believed to be applicable in a wide variety of systems comprising one or more embodiments of the disclosure. As such, the drawings are not meant to include all conventional features known by those of ordinary skill in the art to be required for the practice of the embodiments disclosed herein. 
       DETAILED DESCRIPTION 
       [0019]    In the following specification and the claims, reference will be made to a number of terms, which shall be defined to have the following meanings. 
         [0020]    The singular forms “a”, “an”, and “the” include plural references unless the context clearly dictates otherwise. 
         [0021]    “Optional” or “optionally” means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where the event occurs and instances where it does not. 
         [0022]    Approximating language, as used herein throughout the specification and claims, may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “about”, “approximately”, and “substantially”, are not to be limited to the precise value specified. In at least some instances, the approximating language may correspond to the precision of an instrument for measuring the value. Here and throughout the specification and claims, range limitations may be combined and/or interchanged, and such ranges are identified and include all the sub-ranges contained therein unless context or language indicates otherwise. 
         [0023]    The following detailed description illustrates embodiments of the disclosure by way of example and not by way of limitation. It is contemplated that the disclosure has general application to systems and methods for actuating movable components of gas turbine engines using micro-electromechanical systems (MEMS) technology-based actuators. 
         [0024]    Embodiments of the actuation systems utilizing MEMS technology described herein effectively actuate movable components of gas turbine engines such as variable stator vanes (VSVs) and variable bleed valve (VBV) doors without using dedicated hydraulic lines or dedicated pressure sources such as hydraulic pumps. Also, the actuation systems utilizing MEMS technology described herein enable individual modulation of VSV stages and VBV doors in gas turbine engines to accomplish, for example, active stall control for higher pressure ratios. Further, the actuation systems utilizing MEMS technology described herein utilize MEMS-based mechanisms including, without limitation, piezoelectric effects, to generate rapid pulses with small displacements of an internally contained hydraulic medium, which coupled to an amplifier is able to achieve the necessary displacements required for VBV door and VSV control. Furthermore, the actuation systems utilizing MEMS technology described herein facilitate increased actuation ability of movable components of gas turbine engines such as VSVs and VBV doors within a smaller space envelope, using simpler packaging, and at a lesser weight relative to known piston-based actuation systems. 
         [0025]      FIG. 1  is a schematic illustration of an exemplary gas turbine engine  100 . Gas turbine engine  100  includes a gas generator or core engine  102  that includes a high pressure compressor (HPC)  104 , a combustor assembly  106 , and a high pressure turbine (HPT)  108  in an axial serial flow relationship on a core engine rotor  110  rotating about a core engine shaft  112 . HPC  104 , combustor assembly  106 , HPT  108 , core engine rotor  110 , and core engine shaft  112  are located inside of an annular housing  114 . Gas turbine engine  100  also includes a low pressure compressor (LPC) or fan  116  and a low pressure turbine (LPT)  118  arranged in an axial flow relationship on a power engine rotor  120 . 
         [0026]    In operation, in the exemplary gas turbine engine  100 , air flows along a central axis  122 , and compressed air is supplied by HPC  104 . The highly compressed air is delivered to combustor assembly  106 . Exhaust gas flows (not shown in  FIG. 1 ) from combustor assembly  106  and drives HPT  108  and LPT  118 . Power engine shaft  124  drives power engine rotor  120  and fan  116 . Gas turbine engine  100  also includes a fan or LPC containment case  126 . Also, in the exemplary gas turbine engine  100 , an initial air inlet  128  located at the forward end of gas turbine engine  100  includes an annular inlet cowling  130  defining a circumferential boundary thereof. Throughout gas turbine engine  100 , valves of various types, not shown, are present and control flow of various liquids and gases including, without limitation, fuel, intake air, and exhaust gas. At least some valves in gas turbine engine  100  establish temperature gradients between fluids and gases whereby fluids and gases on one side of the valve are at a higher or lower temperature than the other side of the valve. Further, gas turbine engine  100  includes an aft end including an exhaust outlet  132 . 
         [0027]      FIG. 2  is a schematic illustration of a portion of HPC  104  that may be used in the gas turbine engine  100  shown in  FIG. 1 . HPC  104  includes an inlet  202 . Inlet  202  is the start of the main flowpath of air into HPC  104 . HPC  104  also includes an axially-elongate annular spool  204  mounted for rotation about a centerline axis  206 . Annular spool  204  may be built up from several smaller components. As such, annular spool  204  includes at least one drum portion  208  and at least one annular disk  210  which all rotate together as a unit. Annular spool  204  is depicted in half-section but it will be understood that it is a body of revolution. A plurality of blade rows  212  are carried at the outer periphery of annular spool  204 . Each blade row  212  of the plurality of blade rows  212  includes an annular array of airfoil-shaped compressor blades  214  which extend radially outward from annular spool  204 . An annular liner assembly  216  closely surrounds compressor blades  214  and defines the radially outer boundary of a primary gas flowpath through HPC  104 . Liner assembly  216  is built up from a plurality of smaller components, some of which will be described in more detail below. An annular casing  218  surrounds liner assembly  216  and provides structural support to it. Several stator rows are carried by liner assembly  216 . Each stator row comprises an annular array of airfoil-shaped stator vanes  220  which extend radially inward from liner assembly  216 . Stator rows alternate with blade rows in the axial direction. Each blade row and the axially downstream stator row constitute a “stage” of HPC  104 . 
         [0028]    Also, in the exemplary HPC  104 , the stages of HPC  104  which are shown are labeled sequentially “S 1 ” through “S 7 ”. These numbers are used solely for the sake of easy reference and do not necessarily correspond to the actual number of the stages in the complete HPC  104 . The four stages S 1  through S 4  shown on the left side of the figure (towards inlet  202  end of HPC  104 ) incorporate VSVs. Stator vanes  220  of these stages are constructed so that their angle of incidence can be changed in operation (i.e., these stator vanes  220  can be pivoted about the radial axes shown in dashed lines). The remaining stages to the right side of the figure (towards an exit end of the compressor, not shown) do not incorporate VSVs. Stator vane  220  of each stage S 1  through S 4  has a corresponding trunnion  222  (generically referred to as  222  and labeled  222 A through  222 D, respectively) that extends radially outward through liner assembly  216  and casing  218 . An actuator arm (generically referred to as  224  and labeled  224 A through  224 D, respectively) is attached to radially outward ends of trunnions  222 A- 222 D. All actuator arms  224 A- 224 D for an individual stage are coupled together by a ring  226  (generically referred to as  226  and labeled  226 A through  226 D, respectively). A plurality of actuator arms  224 A- 224 D are rotatable coupled to a plurality of rings  226 A- 226 D in HPC  104 . 
         [0029]    In operation, HPC  104  draws air through inlet  202  and compresses it as it pumps it axially downstream. Each stage contributes an incremental pressure rise to the air, with the highest pressure being at the exit of the last stage. Combined with the constriction in diameter of the main flowpath, the effect is to eject highly compressed air through HPC  104  toward combustor assembly  106 , not shown, at a high velocity and pressure. Rotation of rings  226 A- 226 D about centerline axis  206  causes all actuator arms  224  coupled to that specific ring  226 A- 226 D to move in unison, in turn pivoting all trunnions  222 A- 222 D with their attached VSV-type stator vanes  220  in unison. VSVs enable throttling of flow through HPC  104  so that it can operate efficiently at both high and low mass flow rates. Consequently, rotation of at least one of rings  226 A- 226 D enables at least one of the VSVs to assume required angles of incidence relative to incoming air in the main flowpath of HPC  104 . 
         [0030]      FIG. 3  is a perspective and cross-sectional schematic diagram of a portion of the exemplary HPC  104  shown in  FIG. 2 . As shown and described above with reference to  FIG. 2 , HPC  104  includes inlet  202 , rings  226 A- 226 D, actuator arms  224 A- 224 D, trunnions  222 A- 222 D, and stator vanes  220  coupled thereto. Also, in the exemplary HPC  104 , stator vanes  220  are VSVs coupled to trunnions  222 A- 222 D of stages S 1  through S 4 . Operation of the exemplary embodiment is as described above with reference to  FIG. 2 . Additional numbered features of exemplary HPC  104  are shown in  FIG. 3  to facilitate cross-referencing  FIG. 3  with  FIGS. 1 and 2 . 
         [0031]      FIG. 4  is an aft-to-forward perspective view of an exemplary actuation system utilizing MEMS  400  that may be used in HPC  104  shown in  FIGS. 2 and 3 . In the exemplary embodiment, actuation system utilizing MEMS  400  includes a MEMS actuator  402  (generically referred to as  402  and labeled  402 A through  402 D, respectively) coupled to at least a portion of liner assembly  216 . In other alternative embodiments, not shown, MEMS actuator  402  is coupled to other portions of gas turbine engine  100 , not shown, other than liner assembly  216 , or to combinations thereof. MEMS actuator  402  includes a piston assembly  404  (generically referred to as  404  and labeled  404 A through  404 D, respectively). Piston assembly  404  extends laterally from actuator  402 , and is configured to alternately move laterally outward, i.e., extend, and laterally inward, i.e., retract, in response to commands from a controller, not shown in  FIG. 4 . Also, in the exemplary embodiment, a distal end  406  (generically referred to as  406  and labeled  406 A through  406 D, respectively) of each piston assembly  404  of piston assemblies  404 A- 404 D is coupled to at least one bracket  408  at a radially outward portion thereof. At least one radially inward portion of bracket  408  is coupled to an axially aft side of each ring  226  of the plurality of rings  226 A- 226 D. In other alternative embodiments, not shown, at least one radially inward portion of bracket  408  is coupled to an axially forward side of each ring  226  of the plurality of rings  226 A- 226 D. Additional numbered features of exemplary actuation system utilizing MEMS  400  are shown in  FIG. 4  to facilitate cross-referencing  FIG. 4  with foregoing figures. 
         [0032]    In operation, in the exemplary embodiment, actuation system utilizing MEMS  400  is configured for actuating rotation of VSVs in HPC  104 . As shown and described above with reference to  FIGS. 2 and 3 , rings  226 A- 226 D surround liner assembly  216  of HPC  104 . A plurality of actuator arms  224 A- 224 D are rotatably coupled to radially outward surfaces of rings  226 A- 226 D. In other alternative embodiments, not shown, the plurality of actuator arms  224 A- 224 D are rotatably coupled to radially inward surfaces of rings  226 A- 226 D. Actuator arms  224 A- 224 D extend axially forward from rings  226 A to  226 D and are coupled to trunnions  222 A- 222 D, which penetrate through liner assembly  216 . In an alternative embodiment, not shown, actuator arms  224 A- 224 D extend axially aft from rings  226 A to  226 D. On radially inward surfaces of liner assembly  216 , radially outward ends of VSVs, not shown, are coupled to radially inward ends of trunnions  222 A- 222 D, as shown and described above with reference to  FIG. 2 . The alternating extension and retraction of piston assemblies  404 A- 404 D exerts a force upon rings  226 A- 226 D, thereby rotating rings  226 A- 226 D alternately clockwise and counterclockwise with respect to centerline axis  206 , not shown. With the resulting circumferential movement of rings  226 A- 226 D, VSVs are likewise rotated alternately clockwise and counterclockwise in response to commands from a controller, not shown. Consequently, rotation of at least one of rings  226 A- 226 D enables at least one of the VSVs to assume required angles of incidence relative to incoming air in the main flowpath of HPC  104 . 
         [0033]      FIG. 5  is a forward-to-aft perspective and cross-sectional schematic diagram of an exemplary fan frame  500  which may be used in the gas turbine engine  100  shown in  FIG. 1 . Fan frame  500  includes a plurality of fan frame struts  502  coupled to and disposed within a fan outer guide vane (OGV) support ring  504 . Also, in the exemplary embodiment, each fan frame strut  502  of the plurality of fan frame struts  502  is coupled to and between fan OGV support ring  504  and an annular inner casing  506 . Annular inner casing  506  includes an inner hub bearing support structure  507  circumscribing a void in an aft portion of annular inner casing  506 . Further, in the exemplary embodiment, fan OGV support ring  504  and annular inner housing are arranged circumferentially about centerline axis  206 , and fan frame struts  502  are arranged radially about axis centerline  206 . Furthermore, in the exemplary embodiment, a plurality of variable bleed valve (VBV) doors  508  are arranged circumferentially about centerline axis  206 . Each VBV door  508  of the plurality of VBV doors  508  is disposed circumferentially about centerline axis  206  between two adjacent fan frame struts  502 . Moreover, in the exemplary embodiment, fan frame  500  includes an annular aft plate  510  extending radially inward from radially inward surfaces of aft portions of annular fan casing. Radially inward edges of annular aft plate  510  include generally forward extending lips  512  to which VBV doors  508  are coupled, as further shown and described below with reference to  FIG. 6 . 
         [0034]    In operation, in the exemplary fan frame  500 , fan frame struts  502  serve as structural members (sometimes referred to as “fan struts”) which connect outer fan OGV support ring  504  to annular inner casing  506 . However, in other alternative embodiments, not shown, these support functions may be served by separate components. VBV doors  508  actuate alternately radially inward and radially outward to alternately close and open the space defined between adjacent fan frame struts  502 , as further shown and described below with reference to  FIG. 6 . 
         [0035]      FIG. 6  is a forward-to-aft perspective and sectional view of an exemplary actuation system utilizing MEMS  600  which may be used in fan frame  500  shown in  FIG. 5 . In the exemplary embodiment, a radially inward and aft edge of VBV door  508  is coupled to lip  512  at a hinge  602 . Also, in the exemplary embodiment, actuation system utilizing MEMS  600  includes MEMS actuator  402  coupled to VBV door  508  at generally forward portions thereof. MEMS actuator  402  includes piston assembly  404  extending aftward therefrom. Piston assembly  404  is coupled to at least a portion of annular aft plate  510  at distal end  406 , i.e., an aft end of piston assembly  404 . 
         [0036]    In operation, in the exemplary actuation system utilizing MEMS  600 , MEMS actuator  402  is configured for actuating rotation of VBV door  508  about hinge  602 . As shown and described above with reference to  FIG. 5 , a plurality of VBV doors  508  arranged circumferentially about centerline axis  206  are actuated by a plurality of MEMS actuators  402  alternately radially inward and radially outward to alternately close and open the space defined between adjacent fan frame struts  502 . The space defined between adjacent fan frame struts  502  includes inlet  202  into HPC  104 , not shown. The alternating extension and retraction of piston assembly  404  from MEMS actuator  402  exerts a force upon VBV door  508  about hinge  602 , thereby facilitating control of air flow into inlet  202  of HPC  104 . Also, in operation of the exemplary embodiment, each VBV door  508  of the plurality of VBV doors  508  of fan frame  500  are individually actuateable by individually coupled MEMS actuators  402  coupled thereto. 
         [0037]    Also, in operation of the exemplary actuation system utilizing MEMS  600 , individual actuation of individual VBV doors  508  is advantageous in gas turbine engines  100  under operating conditions including, without limitation, non-axisymmetric inlet flow conditions. Further, in operation of the exemplary actuation system utilizing MEMS  600 , secondary air systems in gas turbine engines  100 , not shown, are bled from at least one VBV door outlet  604  to enable improved secondary air flow by facilitating additional air flow at individual VBV door  508  locations. In other alternative embodiments, not shown, each MEMS actuator  402  of the plurality of MEMS actuators may be configured to actuate all VBV doors  508  in fan frame  500  at the same time, i.e., on the same schedule. In still other embodiments, not shown, subsets of MEMS actuators  402  of the plurality of MEMS actuators in fan frame  500  may be configured to subsets of VBV doors  508  at the same time, including, without limitation, quadrants of VBV doors  508 . 
         [0038]      FIG. 7  is a cross-sectional view of an exemplary embodiment of a MEMS actuator assembly  700  which may be used in the gas turbine engine  100  shown in  FIG. 1 . In the exemplary embodiment, MEMS actuator assembly  700  includes MEMS actuator  402 . MEMS actuator  402  includes a MEMS module  702  coupled to a diaphragm  704 . MEMS actuator  402  includes a sealed body  705 , i.e., a pump, defined by the outside walls of MEMS actuator  402 . Sealed body  705  further defines an interior of MEMS actuator  402 , i.e., an interior of a pump. Inside of MEMS actuator  402  is coupled a first one-way valve  706  separating a first cavity  708  from a second cavity  710 . MEMS actuator  402  also includes a piston head  712  from which a piston shaft  713  of piston assembly  404  extends axially outside of MEMS actuator  402  along an axis  714 . Second cavity  710  is defined between a piston head  712  and first one-way valve  706 . MEMS actuator  402  further includes a spring  716 , i.e., as a bias member. Spring  716  is disposed circumferentially around a piston assembly  404 . Spring  716  extends axially inside of MEMS actuator  402  along a piston assembly  404  between a piston head  712  and a piston exit  718 . As such, spring  716  resides within a third cavity  720  inside of MEMS actuator  402 . 
         [0039]    Also, in the exemplary embodiment, MEMS actuator assembly  700  includes a first hydraulic line  722  extending between third cavity  720  and first cavity  708 . MEM actuator assembly  700  also includes a second hydraulic line  724  extending between third cavity  720  and second cavity  710 . A second one-way valve  726  permits flow through first hydraulic line  722  from third cavity  720  to first cavity  708 . A reset valve  728  permits flow between third cavity  720  and second cavity  710 . 
         [0040]    Further, in the exemplary embodiment, MEMS actuator assembly  700  includes a MEMS controller  730  communicatively coupled to MEMS module  702 . MEMS controller  730  is configured to transmit a MEMS control signal  732  to MEMS module  702  to facilitate commanded alternating movement of diaphragm  704 . Diaphragm  704  separates first cavity  708  from a fourth cavity  734  within which MEMS module  702  resides inside of MEMS actuator  402 . In alternative embodiments, not shown, MEMS module  702  resides in or on other portions of MEMS actuator  402 . Furthermore, in the exemplary embodiment, first one-way valve  706  and second one-way valve  726  are passive, i.e., uncontrolled, valves. 
         [0041]    MEMS controller  730  is configured to transmit a reset valve control signal  736  to reset valve  728  to facilitate commanded alternating opening and closing of reset valve  728 . In an alternative embodiment, not shown, MEMS controller is further configured to transmit at least one of a first one-way valve control signal  738  to first one-way valve  706  and a second one-way valve control signal  740  to facilitate commanded alternating opening and closing of first one-way valve  706  and second one-way valve  726 , respectively. MEMS actuator assembly  700  includes at least one position sensor  742  coupled to MEMS actuator  402  along interior surfaces thereof facing second cavity  710  and third cavity  720 . In alternative embodiments, not shown, position sensor(s)  742  are not present, or are coupled to or on other portions of MEMS actuator  402 . Position sensor  742  is configured to detect a present position of piston assembly  404 , including, without limitation, the present position of piston head  712 , and transmit a position feedback signal  744  to MEMS controller  730  to facilitate comparison and correction between a commanded position of piston assembly  404  and the present position of piston assembly  404 , as further described below with reference to  FIG. 8 . In other alternative embodiments, not shown, MEMS controller  730  transmits and receives signals other than MEMS control signal  732 , reset valve control signal  736 , and position feedback signal  744  to and from elsewhere in either actuation system utilizing MEMS  400  or actuation system utilizing MEMS  600 , or both. In still other alternative embodiments, not shown, at least one of first one-way valve  706  and second one-way valve  726  are replaced with two-way valves in the same positions thereof, thus facilitating positive travel of piston assembly  404  in two directions in MEMS actuator assembly  700 . 
         [0042]    In operation each of first cavity  708 , second cavity  710 , third cavity  720 , first hydraulic line  722 , and second hydraulic line  724  are filled with a hydraulic fluid. MEMS actuator assembly  700  is configured to establish and maintain at least four operational states for piston assembly  404 : extension (distal end  406  moving to the right of  FIG. 7 ), retraction (distal end  406  moving to the left of  FIG. 7 ), stationary (piston assembly  404  does not move, but rather maintains its current position), and equilibration (piston assembly  404  is able to move freely in any direction). 
         [0043]    In operation, to facilitate extension, MEMS controller  730  commands reset valve  728  to close, and further commands MEMS module  702  to initiate MEMS-based movement of diaphragm  704  including, without limitation, alternating and pulsating movement via piezoelectric effects. Movement of diaphragm  704  facilitates increased hydraulic pressure in first cavity  708  and, thereby in second cavity  710 , through flow of hydraulic fluid through first one-way valve  706 . Such increased hydraulic pressure in second cavity  710  exerts a force upon piston head  712  to move it to the right in  FIG. 7 . Simultaneously with rightward movement of piston assembly  404 , spring  716  undergoes compression facilitating potential energy storage therein. As piston head  712  extends to the right, increased hydraulic pressure in third cavity  720  is relieved to first cavity  708  via second one-way valve  726 . The ordering and timing of commanded movement of diaphragm  704 , including, without limitation, the number of pulses, dictate both the rate of and extent of extension of piston assembly  404 . 
         [0044]    In further operation, to facilitate retraction, MEMS controller  730  commands reset valve  728  to open. Opening of reset valve  728  facilitates equalization of hydraulic pressure between second cavity  710  and third cavity  720 . As such, potential energy stored in spring  716  is converted into kinetic energy whereby spring  716  extends leftward and exerts a force upon piston head  712  facilitating movement of piston assembly  404  to the left in  FIG. 7 . The ordering and timing of commanded alternating opening and closing of reset valve  728  dictate both the rate of and extent of retraction of piston assembly  404  in the exemplary embodiment. 
         [0045]    In still further operation, to facilitate the stationary operational state, MEMS controller  730  commands reset valve  728  to close. The stationary operational state is further facilitated by MEMS controller  730  not commanding movement of diaphragm  704 . As a result, an equilibrium state is reached whereby the rightward force exerted upon piston head  712  by increased hydraulic pressure in second cavity  710  is balanced by the leftward force exerted upon piston head  712  by spring  716 , in addition to forces exerted upon piston assembly  404  by movable components, not shown, of gas turbine engine  100 , e.g., VSVs and VBV doors. Therefore, in the stationary operational state, piston assembly  404  remains stationary and does not move either to the left or to the right in  FIG. 7 . 
         [0046]    In yet further operation, to facilitate the equilibration operational state, MEMS controller  730  commands reset valve  728  to open. The equilibration operational state is further facilitated by MEMS controller  730  not commanding movement of diaphragm  704 . As a result, any difference in hydraulic pressures amongst first cavity  708 , second cavity  710 , and third cavity  720  is extinguished, and spring  716  exerts a force upon piston head  712  to the right in  FIG. 7  which tends to return piston assembly  404  to a fully retracted position. As such, it is possible for piston assembly  404 , along with movable components, not shown, of gas turbine engine  100  attached thereto, to be moved manually. Placement of MEMS actuator assembly  700  into the equilibration operational state is advantageous in gas turbine engine  100  during, by way of example, maintenance activities thereupon. 
         [0047]      FIG. 8  is a schematic view of an exemplary control scheme  800  which may be used with the MEMS actuator assembly  700  shown in  FIG. 7 . In the exemplary embodiment, control scheme  800  includes a main engine controller  802 , including, without limitation, a full authority digital engine (or electronics) control (FADEC), configured to receive operator-initiated commands for desired operational states of gas turbine engine  100 , including, without limitation, positional states of VSV-type stator vanes  220  and VBV doors  508 . Main engine controller  802  is further configured to transmit positional commands, including, without limitation, actuator commands  804  representing the desired position(s) of VSV-type stator vane(s)  220  and VBV door(s)  508 , to MEMS controller  730 . As shown and described above with reference to  FIG. 7 , MEMS controller  730  transmits at least one of MEMS control signal  732  and reset valve control signal  736  to MEMS actuator  402 . 
         [0048]    Also, in the exemplary control scheme  800 , MEMS actuator  402  effects actuation of movable components of gas turbine engine  100  including, without limitation, VSV-type stator vane(s)  220  and VBV door(s)  508 , via controlled movements  806  thereof. Controlled movements  806  of movable components of gas turbine engine  100  such as VSV-type stator vane(s)  220  and VBV door(s)  508  effect variations of the kinematics of gas turbine engine  100 . Further, in the exemplary control scheme  800 , MEMS actuator  402  includes at least one position sensor  742  configured to detect the present position of piston assembly  404 , not shown, in MEMS actuator  402 . Position sensor  742  is further configured to transmit a position feedback signal  744  to MEMS controller  730  to facilitate comparison and correction between the commanded position of piston assembly  404  and the present position of piston assembly  404 . Upon receipt of position feedback signal  744  by MEMS controller  730 , MEMS controller compares the present, i.e., resultant, position of piston assembly  404  with the commanded position of piston assembly  404  intended by the operator of gas turbine engine  100 . Any deviation from the aforementioned two piston assembly  404  positions is corrected by MEMS controller  730 , if necessary, by the issuance of at least one additional corrective control signal, including at least one additional MEMS control signal  732 , reset valve control signal  736 , first one-way valve control signal  738 , and second one-way valve control signal  740  to MEMS actuator  402 . As such, control scheme  800  facilitates continuous closed loop feedback for operators of gas turbine engines  100  to effect desired variations in the kinematics thereof. 
         [0049]    The above-described embodiments of actuation systems utilizing MEMS technology effectively actuate movable components of gas turbine engines such as variable stator vanes (VSVs) and variable bleed valve (VBV) doors without using dedicated hydraulic lines. Also, the above-described embodiments of actuation systems utilizing MEMS technology make it possible to effect individual modulation of VSV stages and VBV doors in gas turbine engines to accomplish, for example, active stall control for higher pressure ratios. Further, the above-described embodiments of actuation systems utilizing MEMS technology utilize MEMS-based mechanisms including, without limitation, piezoelectric effects, to generate rapid pulses with small displacements of an internally contained hydraulic medium, which coupled to an amplifier is able to achieve the larger displacements required for VBV door and VSV control. Furthermore, the above-described embodiments of actuation systems utilizing MEMS technology facilitate increased actuation ability of movable components of gas turbine engines such as VSVs and VBV doors within a smaller space envelope, using simpler packaging, and at a lesser weight relative to known piston-based actuation systems. 
         [0050]    Example systems and apparatus of actuation systems utilizing MEMS technology are described above in detail. The apparatus illustrated is not limited to the specific embodiments described herein, but rather, components of each may be utilized independently and separately from other components described herein. By way of example only, systems and apparatus of actuation systems utilizing MEMS technology may be used with movable components of gas turbine engines other than VSVs and VBV doors, including, without limitation, variable area bypass injectors (VABIs), variable area turbine nozzles (VATNs), variable exhaust nozzles (VENs), thrust reversers, and blocker doors, and any other actuated device found in any other system which similarly benefits from actuation systems utilizing MEMS technology described above. Each system component can also be used in combination with other system components. 
         [0051]    This written description uses examples to describe the disclosure, including the best mode, and also to enable any person skilled in the art to practice the disclosure, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the disclosure is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.