Patent Publication Number: US-11391301-B2

Title: Electrohydraulic poppet valve device control that maintains the last commanded position of a device upon power interruption and provides back-up position control

Description:
TECHNICAL FIELD 
     The present disclosure generally relates to devices controlled by electrohydraulic valves and more particularly relates to a system that, upon power interruption, maintains the last commanded position of a device that is controlled by an electrohydraulic poppet valve device control, and provides back-up position control of that device. 
     BACKGROUND 
     The position of a controlled device, such as an actuator or a valve, may be either electrically controlled, via a motor, or hydraulically controlled, via an electrohydraulic servo valve arrangement. Depending on the particular end-use environment of the device, it may be desirable to maintain the device in the last commanded position (i.e., “fail-fixed”) in the unlikely event of a power interruption. For example, many fuel metering valves that control fuel flow to gas turbine propulsion engines are required to maintain the last commanded position in the unlikely event of a power interruption. As another example, many engines that include compressor inlet guide vanes also include a requirement that the guide vanes remain in the last commanded position in the unlikely event of a power interruption. A need also exists for back-up position control of these devices. 
     The fail-fixed functionality for many fuel metering valves is implemented using a stepper motor. Although stepper motors are robust and reliable, these devices can exhibit certain drawbacks. For example, stepper motors can draw relatively high electrical power from the associated controller. Moreover, for electrical redundancy, a second stepper motor and a summing gearbox may also be needed, which results in increased weight of the control, cabling, and engine. Some stepper motors also provide a relatively low force output, which may limit continued operability in environments where contaminated fuel is possible. Additionally, stepper motor driven metering valves are not easily adaptable for back-up position control. 
     For compressor inlet guide vanes, the fail-fixed functionality options are relatively limited. Stepper motors can be used but, when used, typically rely on relatively complicated mechanical feedback systems to ensure the actuator remains in the last commanded position. Other options include using a lockout valve that is activated by a solenoid or similar signal to hydraulically lock the actuator. This option, however, adds additional weight and complexity to the controller and engine, and are not easily adaptable for back-up position control. 
     Hence, there is a need for a system that maintains the last commanded position of a controlled device upon power interruption that adds little or no cost, little or no complexity, little or no size, and little or no weight to existing systems, and provides back-up position control of the device. The present invention addresses at least this need. 
     BRIEF SUMMARY 
     This summary is provided to describe select concepts in a simplified form that are further described in the Detailed Description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. 
     In one embodiment, an electrohydraulic poppet valve device control system includes a main body, an extend poppet valve, a retract poppet valve, and an actuator. The main body has an extend valve bore and a retract valve bore defined therein. The extend valve bore includes an extend valve inlet port, an extend valve outlet port, an extend valve control pressure port, and an extend valve return pressure port. The retract valve bore includes a retract valve inlet port, a retract valve outlet port, a retract valve control pressure port, and a retract valve return pressure port. The extend poppet valve is disposed within the extend valve bore and is movable therein between a closed position, in which the extend valve inlet port is fluidly isolated from the extend valve outlet port, and an open position, in which the extend valve inlet port is in fluid communication with the extend valve outlet port. The retract poppet valve is disposed within the retract valve bore and is movable therein between a closed position, in which the retract inlet port is fluidly isolated from the retract valve outlet port, and an open position, in which the retract inlet port is in fluid communication with the retract valve outlet port. The actuator includes an actuator supply pressure port, an actuator return pressure port, an extend control pressure port, and a retract control pressure port. The actuator return pressure port is in fluid communication with the extend valve return pressure port and the retract valve return pressure port. The extend control pressure port is in fluid communication with the extend valve control pressure port. The retract control pressure port is in fluid communication with the retract valve control pressure port. The actuator is movable to an extend position, a retract position, and a null position. In the extend position, the actuator supply pressure port is in fluid communication with the extend valve control pressure port and the actuator return pressure port is in fluid communication with the retract valve control pressure port, thereby causing the extend poppet valve to be in its open position and the retract poppet valve to be in its closed position. In the retract position, the actuator supply pressure port is in fluid communication with the retract valve control pressure port and the actuator return pressure port is in fluid communication with the extend valve control pressure port, thereby causing the extend poppet valve to be in its closed position and the retract poppet valve to be in its open position. In the null position, the actuator supply pressure port and the actuator return pressure port are fluidly coupled to both of the extend valve control pressure port and the retract valve control pressure port, thereby causing the extend poppet valve to be in its closed position and the retract poppet valve to be in its closed position. The actuator moves to, or remains in, the null position when electrical power is not supplied to the actuator. 
     In another embodiment, an electrohydraulic poppet valve device control system includes a main body, an extend poppet valve, a retract valve body, a retract poppet valve, an actuator, a device housing, and a device. The main body has an extend valve bore and a retract valve bore defined therein. The extend valve bore includes an extend valve inlet port, an extend valve outlet port, an extend valve control pressure port, and an extend valve return pressure port. The retract valve bore includes a retract valve inlet port, a retract valve outlet port, a retract valve control pressure port, and a retract valve return pressure port. The extend poppet valve is disposed within the extend valve bore and is movable therein between a closed position, in which the extend valve inlet port is fluidly isolated from the extend valve outlet port, and an open position, in which the extend valve inlet port is in fluid communication with the extend valve outlet port. The retract poppet valve is disposed within the retract valve bore and is movable therein between a closed position, in which the retract inlet port is fluidly isolated from the retract valve outlet port, and an open position, in which the retract inlet port is in fluid communication with the retract valve outlet port. The actuator includes an actuator supply pressure port, an actuator return pressure port, an extend control pressure port, a retract control pressure port, a jet tube, and a three-channel torque motor. The actuator return pressure port is in fluid communication with the extend valve return pressure port and the retract valve return pressure port. The extend control pressure port is in fluid communication with the extend valve control pressure port. The retract control pressure port is in fluid communication with the retract valve control pressure port. The jet tube is in fluid communication with the actuator supply pressure port and is movable to an extend position, a retract position, and a null position. The three-channel torque motor is coupled to the jet tube and responsive to commands to move the jet tube. The device housing has an inner surface, an outer surface, and at least one actuation control pressure port. The inner surface defes a device cavity, and the at least one actuation control pressure port is in fluid communication with the extend valve outlet port and the retract valve outlet port. The device is disposed at least partially in, and movable within, the device cavity. The device is movable in response to at least fluid pressure in the at least one actuation control pressure port. In the extend position, the actuator supply pressure port is in fluid communication with the extend valve control pressure port and the actuator return pressure port is in fluid communication with the retract valve control pressure port, thereby causing the extend poppet valve to be in its open position and the retract poppet valve to be in its closed position. In the retract position, the actuator supply pressure port is in fluid communication with the retract valve control pressure port and the actuator return pressure port is in fluid communication with the extend valve control pressure port, thereby causing the extend poppet valve to be in its closed position and the retract poppet valve to be in its open position. In the null position, the actuator supply pressure port and the actuator return pressure port are fluidly coupled to both of the extend valve control pressure port and the retract valve control pressure port, thereby causing the extend poppet valve to be in its closed position and the retract poppet valve to be in its closed position. The torque motor moves the jet tube to, or causes it to remain in, the null position when electrical power is not supplied to the torque motor. 
     In yet another embodiment, an electrohydraulic poppet valve device control system includes a main body, a first extend poppet valve, a second extend poppet valve, a first retract poppet valve, a second retract poppet valve, and an actuator. The main body has a first extend valve bore, a second extend valve bore, a first retract valve bore, and a second retract valve bore defined therein. The first extend valve bore includes a first extend valve inlet port, a first extend valve outlet port, first extend valve control pressure port, and a first extend valve return pressure port. The second extend valve bore includes a second extend valve inlet port, a second extend valve outlet port, second extend valve control pressure port, and a second extend valve return pressure port. The first retract valve bore includes a first retract valve inlet port, a first retract valve outlet port, a first retract valve control pressure port, and a first retract valve return pressure port. The second retract valve bore includes a second retract valve inlet port, a second retract valve outlet port, a second retract valve control pressure port, and a second retract valve return pressure port. The first extend poppet valve is disposed within the first extend valve bore and is movable therein between a closed position, in which the first extend valve inlet port is fluidly isolated from the first extend valve outlet port, and an open position, in which the first extend valve inlet port is in fluid communication with the first extend valve outlet port. The second extend poppet valve is disposed within the second extend valve bore and is movable therein between a closed position, in which the second extend valve inlet port is fluidly isolated from the second extend valve outlet port, and an open position, in which the second extend valve inlet port is in fluid communication with the second extend valve outlet port. The first retract poppet valve is disposed within the first retract valve bore and is movable therein between a closed position, in which the first retract inlet port is fluidly isolated from the first retract valve outlet port, and an open position, in which the first retract inlet port is in fluid communication with the first retract valve outlet port. The second retract poppet valve is disposed within the second retract valve bore and is movable therein between a closed position, in which the second retract inlet port is fluidly isolated from the second retract valve outlet port, and an open position, in which the second retract inlet port is in fluid communication with the second retract valve outlet port. The actuator includes an actuator supply pressure port, an actuator return pressure port, an extend control pressure port, and a retract control pressure port. The actuator return pressure port is in fluid communication with the extend valve return pressure port, the second extend valve return pressure port, the retract valve return pressure port, and the second retract valve return pressure port. The extend control pressure port is in fluid communication with extend valve control pressure port and the second extend valve control pressure port. The retract control pressure port is in fluid communication with retract valve control pressure port and the second retract valve control pressure port. The actuator is movable to an extend position, a retract position, and a null position. In the extend position, the actuator supply pressure port is in fluid communication with the first extend valve control pressure port and the second extend valve control pressure port, and the actuator return pressure port is in fluid communication with the first retract valve control pressure port and the second retract valve control pressure port, thereby causing the first and second extend poppet valves to be in open positions and the first and second retract poppet valve to be in closed positions. In the retract position, the actuator supply pressure port is in fluid communication with the first retract valve control pressure port and the second retract valve control pressure port, and the actuator return pressure port is in fluid communication with the first extend valve control pressure port and the second extend valve control pressure port, thereby causing the first and second extend poppet valves to be in closed positions and the first and second retract poppet valves to be in open position. In the null position, the actuator supply pressure port and the actuator return pressure port are fluidly coupled to both of the first extend valve control pressure port and the first retract valve control pressure port and from both of the second extend valve control pressure port and the second retract valve control pressure port, thereby causing the first and extend poppet valves and the first and second retract poppet valves to be in closed positions. The actuator moves to, or remains in, the null position when electrical power is not supplied to the actuator. 
     Furthermore, other desirable features and characteristics of the system will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the preceding background. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and wherein: 
         FIG. 1  depicts a schematic representation of one embodiment of an electrohydraulic poppet valve (EHPV) device control system that is coupled to an actuator, requires one control pressure, maintains the last commanded position of the actuator, and provides back-up position control of the actuator; 
         FIGS. 2-4  depict the EHPV device control system of  FIG. 1  in fixed, extend, and retract functional modes, respectively; 
         FIG. 5  depicts a schematic representation of another embodiment of an EHPV device control system that is coupled to an actuator, requires two control pressures, maintains the last commanded position of the actuator, and provides back-up position control of the actuator; 
         FIGS. 6-8  depict the EHPV device control system of  FIG. 5  in fixed, extend, and retract functional modes, respectively; 
         FIGS. 9-11  depict another embodiment of an EHPV device control system that requires two control pressures, in fixed, extend, and retract functional modes, respectively; 
         FIG. 12  depicts the EHPV device control system of  FIG. 1  coupled to a metering valve and that requires one control pressure; and 
         FIG. 13  depicts the EHPV device control system of  FIG. 5  coupled to a metering valve and that requires two control pressures. 
     
    
    
     DETAILED DESCRIPTION 
     The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. As used herein, the word “exemplary” means “serving as an example, instance, or illustration.” Thus, any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments. All of the embodiments described herein are exemplary embodiments provided to enable persons skilled in the art to make or use the invention and not to limit the scope of the invention which is defined by the claims. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary, or the following detailed description. 
     Referring now to  FIG. 1 , a system  100 , and more specifically an electrohydraulic poppet valve (EHPV) device control system  100  that controls the position of a device  110 , and that maintains the last commanded position of the device  110  upon power interruption to the (EHPV) device control system  100 , is depicted. The system  100  includes a main body  101 , an extend valve  102 , a retract valve  104 , and an actuator  106 , and is in fluid communication with the device  110  whose position it is controlling. 
     Referring now to  FIGS. 2-4 , it may be seen that the main body  101  has an extend valve bore  116  and a retract valve bore  136  defined therein. The extend valve bore  116  includes an extend valve inlet port  118 , an extend valve outlet port  122 , an extend valve control pressure port  124 , and an extend valve return pressure port  126 . 
     An extend poppet valve  112  is disposed within the extend valve bore  116  and is movable therein between an open position and a closed position. In the closed position, which is the position depicted in  FIGS. 1, 2, and 4 , the extend valve inlet port  118  is fluidly isolated from the extend valve outlet port  122 . In the open position, which is the position depicted in  FIG. 3 , the extend valve inlet port  118  is in fluid communication with the extend valve outlet port  122 . 
     The depicted extend valve  102  also includes an extend valve spring  127 . The extend valve spring  127  is disposed within the extend valve bore  116  and engages the main body  101  and the extend poppet valve  112 . More specifically, the extend valve spring  127  is disposed within an extend valve spring chamber  131  that is defined between the main body and the extend poppet valve  112 . The extend valve spring  127  supplies a spring force to the extend poppet valve  112  that urges the extend poppet valve  112  toward its closed position. 
     The retract valve bore  136  includes a retract valve inlet port  138 , a retract valve outlet port  142 , a retract valve control pressure port  144 , and a retract valve return pressure port  146 . 
     A retract poppet valve  132  is disposed within the retract valve bore  136  and is movable therein between a closed position and an open position. In the closed position, which is depicted in  FIGS. 1-3 , the retract valve inlet port  138  is fluidly isolated from the retract valve outlet port  142 . In the open position, which is the position depicted in  FIG. 4 , the retract valve inlet port  138  is in fluid communication with the retract valve outlet port  142 . 
     The depicted retract valve  104  also includes a retract valve spring  129 . The retract valve spring  129  is disposed within the retract valve bore  136  and engages the main body  101  and the retract poppet valve  132 . More specifically, the retract valve spring  129  is disposed within a retract valve spring chamber  133  that is defined between the main body  101  and the retract poppet valve  132 . The retract valve spring  129  supplies a spring force to the retract poppet valve  132  that urges the retract poppet valve  132  toward its closed position. 
     The actuator  106  includes an actuator supply pressure port  148 , an actuator return pressure port  152 , an extend control pressure port  154 , and a retract control pressure port  156 . The actuator return pressure port  152  is in fluid communication with the extend valve return pressure port  126  and the retract valve return pressure port  146 , the extend control pressure port  154  is in fluid communication with extend valve control pressure port  124 , and the retract control pressure port  156  is in fluid communication with retract valve control pressure port  144 . As  FIGS. 1-4  also show, the actuator supply pressure port  148  is adapted to receive a flow of pressurized fluid, at a supply pressure (PS), from a non-illustrated fluid source, and the actuator return pressure port  152 , and thus the extend valve return pressure port  126  and the retract valve return pressure port  146 , is in fluid communication with the non-illustrated fluid source at a return pressure (PR). 
     The actuator  106  is movable to an extend position, a retract position, and a null position. In the extend position, which is the position depicted in  FIG. 3 , the actuator supply pressure port  148  is in fluid communication with the extend valve control pressure port  124 , and the actuator return pressure port  152  is in fluid communication with the retract valve control pressure port  144 . As a result, fluid pressure at the extend valve control pressure port  124  (PC 1 ) is at supply pressure (PS) and fluid pressure at the retract valve control pressure port  144  (PC 2 ) is at return pressure (PR). The fluid pressure at the extend valve control pressure port  124  (PC 1 ) overcomes the spring force of the extend valve spring  127  and moves the extend poppet valve  112  to its open position. However, the fluid pressure at the retract valve control pressure port  144  (PC 2 ) is insufficient to overcome the spring force of the retract valve spring  129  and thus the retract poppet valve  132  remains in its closed position. 
     In the retract position, which is the position depicted in  FIG. 4 , the actuator supply pressure port  148  is in fluid communication with the retract valve control pressure port  144 , and the actuator return pressure port  152  is in fluid communication with the extend valve control pressure port  124 . As a result, fluid pressure at the retract valve control pressure port  144  (PC 2 ) is at supply pressure (PS) and fluid pressure at the extend valve control pressure port  124  (PC 1 ) is at return pressure (PR). The fluid pressure at the retract valve control pressure port  144  (PC 2 ) overcomes the spring force of the retract valve spring  129  and moves the retract poppet valve  132  to its open position. However, the fluid pressure at the extend valve control pressure port  124  (PC 1 ) is insufficient to overcome the spring force of the extend valve spring  127  and thus the extend poppet valve  112  remains in its closed position. 
     In the null position, which is the position depicted in  FIGS. 1 and 2 , the actuator supply pressure port  148  and the actuator return pressure port  152  are fluidly coupled to both of the extend valve control pressure port  124  and the retract valve control pressure port  144 . As a result, the fluid pressures at the extend valve control pressure port  124  (PC 1 ) and at the retract valve control pressure port  144  (PC 2 ) are both insufficient to overcome the spring force of the extend valve spring  127  and the retract valve spring  129 , respectively. Thus, the extend poppet valve  112  and the retract valve poppet  132  either move to or remain in the closed positions. 
     The actuator  106  is configured to move to, or remain in, the null position when it is not receiving electrical power. Thus, when electrical power is not supplied to the actuator  106  for any reason, be it removal of a command that causes the actuator  106  to move to its extend or retract position, or in the unlikely event of a loss of electrical power to the actuator  106 , it will move to, or remain in, the null position. 
     Although the actuator  106  may be variously implemented to carry out its functionality, in the depicted embodiment it is implemented as a torque motor jet tube actuator. The depicted actuator  106  thus includes a jet tube  158  and a torque motor  162 . The jet tube  158  is in fluid communication with the actuator supply pressure port  148  and is movable to the extend position, the retract position, and the null position. The torque motor  162  is coupled to the jet tube  158  and is responsive to commands received from a non-illustrated control source to control the position of the jet tube  158 . 
     In a particular preferred embodiment, the torque motor  162 , when included, is implemented using a three-channel torque motor having a first coil  163  (e.g., a FADEC controlled channel A coil) coupled to a first electrical connector  169 , a second coil  165  (e.g., a FADEC controlled channel B coil) coupled to a second electrical connector  171 , and a third coil  167  (e.g., a back-up airframe commanded coil) coupled to a third electrical connector  173 . A distinct advantage to this type of torque motor  162  is that it can continue to function in the unlikely event that one of the first or second coils  163 ,  165  were to become inoperable. It has the further advantage that in the unlikely event both of the first and second coils  163 ,  165  were to become inoperable, the third coil  167  can be intermittently energized by, for example, an aircraft pilot to achieve manual back-up position control of the device  110 . 
     It will be appreciated that in other embodiments, various other types valve actuators or torque motors could be used. No matter the type of valve actuator, however, in the unlikely event that power is interrupted to the system  100  (e.g., the torque motor  162  or other valve actuator), the torque motor  162  (or other valve actuator) is configured to move the jet tube  158  to, or cause it to remain in, the null position, or to intermittently move when back-up control is being used. 
     In another embodiment, which is depicted in  FIGS. 5-8 , the (EHPV) device control system  500  includes the same elements as the system  100  depicted in  FIG. 1 , and additionally includes a second extend valve  502  and a second retract valve  504 . In this additional embodiment, those elements common to the system depicted in  FIGS. 1-4  (though oriented slightly different), and that were described above, are depicted in  FIGS. 5-8  with the same reference numerals, and detailed descriptions thereof will not be repeated. 
     Referring now to  FIG. 6 , it is seen that a second extend valve bore  514  and a second retract valve bore  534  are defined in the main body  101 . The second extend valve bore  514  includes a second extend valve inlet port  516 , a second extend valve outlet port  518 , a second extend valve control pressure port  522 , and a second extend valve return pressure port  524 . 
     A second extend poppet valve  508  is disposed within the second extend valve bore  514  and is movable therein between an open position and a closed position. In the closed position, which is the position depicted in  FIGS. 5, 6, and 8 , the second extend valve inlet port  516  is fluidly isolated from the second extend valve outlet port  518 . In the open position, which is the position depicted in  FIGS. 5 and 7 , the second extend valve inlet port  516  is in fluid communication with the second extend valve outlet port  518 . 
     The depicted second extend valve  502  also includes a second extend valve spring  527 . The second extend valve spring  527  is disposed within the second extend valve bore  514  and engages the main body  101  and the second extend poppet valve  508 . The second extend valve spring  527  supplies a spring force to the second extend poppet valve  508  that urges the second extend poppet valve  508  toward its closed position. 
     The second retract valve bore  534  includes a second retract valve inlet port  536 , a second retract valve outlet port  538 , a second retract valve control pressure port  542 , and a second retract valve return pressure port  544 . 
     A second retract poppet valve  528  is disposed within the second retract valve bore  534  and is movable therein between a closed position and an open position. In the closed position, which is depicted in  FIGS. 5-7 , the second retract valve inlet port  536  is fluidly isolated from the second retract valve outlet port  538 . In the open position, which is the position depicted in  FIG. 8 , the second retract valve inlet port  536  is in fluid communication with the second retract valve outlet port  538 . 
     The depicted second retract valve  504  also includes a second retract valve spring  529 . The second retract valve spring  529  is disposed within the second retract valve bore  534  and engages the main body  101  and the second retract poppet valve  528 . The second retract valve spring  529  supplies a spring force to the second retract poppet valve  528  that urges the second retract poppet valve  528  toward its closed position. 
     As  FIGS. 5-8  further depict, the extend valve control pressure port  124  is in fluid communication with second extend valve control pressure port  522 , and the retract valve control pressure port  144  in is fluid communication with second retract valve control pressure port  542 . Moreover, the actuator return pressure port  152 , in addition to being in fluid communication with the extend valve return pressure port  126  and the retract valve return pressure port  146 , is in fluid communication with the second extend valve return pressure port  524  and the second retract valve return pressure port  544 . The extend control pressure port  154 , in addition to being in fluid communication with the extend valve control pressure port  124 , is in fluid communication with the second extend valve control pressure port  522 , and the retract control pressure port  156 , in addition to being in fluid communication with retract valve control pressure port  144 , is in fluid communication with second retract valve control pressure port  542 . 
     With this embodiment, when the actuator  106  is in the extend position, which is the position depicted in  FIG. 7 , the actuator supply pressure port  148  is in fluid communication with the extend valve control pressure port  124  and the second extend valve control pressure port  522 , and the actuator return pressure port  152  is in fluid communication with the retract valve control pressure port  144  the second retract valve control pressure port  542 . As a result, fluid pressure (PC 2 ) at the extend valve control pressure port  124  and the second extend valve control pressure port  522  is at supply pressure (PS), and fluid pressure (PC 1 ) at the retract valve control pressure port  144  and the second retract valve control pressure port  542  is at return pressure (PR). The fluid pressure (PC 2 ) at the extend valve control pressure port  124  and the second extend valve control pressure port  522  overcomes the spring forces of the extend valve spring  127  and the second extend valve spring  527  and moves the extend poppet valve  112  and the second extend poppet valve  508  to their open positions. However, the fluid pressure (PC 1 ) at the retract valve control pressure port  144  and the second retract valve control pressure port  542  is insufficient to overcome the spring force of the retract valve spring  129  and the second retract valve spring  529 . Thus, the retract poppet valve  132  and the second retract poppet valve  528  remain in their closed positions. 
     When the actuator  106  is in the retract position, which is the position depicted in  FIG. 8 , the actuator supply pressure port  148  is in fluid communication with the retract valve control pressure port  144  and the second retract valve control pressure port  542 , and the actuator return pressure port  152  is in fluid communication with the extend valve control pressure port  124  the second extend valve control pressure port  522 . As a result, fluid pressure (PC 1 ) at the retract valve control pressure port  144  and the second retract valve control pressure port  542  is at supply pressure (PS), and fluid pressure (PC 2 ) at the extend valve control pressure port  124  and the second extend valve control pressure port  522  is at return pressure (PR). The fluid pressure (PC 1 ) at the retract valve control pressure port  144  and the second retract valve control pressure port  542  overcomes the spring forces of the retract valve spring  129  and the second retract valve spring  529  and moves the retract poppet valve  132  and the second retract poppet valve  528  to their open positions. However, the fluid pressure (PC 2 ) at the extend valve control pressure port  124  and the second extend valve control pressure port  522  is insufficient to overcome the spring forces of the extend valve spring  127  and the second extend valve spring  527 . Thus, the extend poppet valve  112  and the second extend poppet valve  508  remain in their closed positions. 
     When the actuator  106  is in the null position, which is the position depicted in  FIGS. 5 and 6 , the actuator supply pressure port  148  and the actuator return pressure port  152  are fluidly coupled to all of the extend valve control pressure port  124 , the second extend valve control pressure port  522 , the retract valve control pressure port  144 , and the second retract valve control pressure port  542 . As a result, the fluid pressure (PC 2 ) at the extend valve control pressure port  124  the second extend valve control pressure port  522 , and the fluid pressure (PC 1 ) at the retract valve control pressure port  144  and the second retract valve control pressure port  542  are insufficient to overcome the spring forces of the springs  127 ,  527  and  129 ,  529 , respectively. Thus, the extend poppet valve  112 , the second extend poppet valve  508 , the retract valve poppet  132 , and the second retract poppet valve  528  either move to or remain in the closed positions. 
     Turning now to  FIGS. 9-11 , yet another embodiment of the (EHPV) device control system  900  is depicted. This embodiment includes the same elements as the system  500  depicted in  FIGS. 5-8  but, as will be described, includes additional ports. In this additional embodiment, those elements common to the system depicted in  FIGS. 5-8 , and that were described above, are depicted in  FIGS. 9-11  with the same reference numerals, and detailed descriptions thereof will not be repeated. 
     In the embodiment depicted in  FIGS. 9-11 , the extend valve bore  116  further includes first and second auxiliary extend valve control pressure ports  902  and  903 , and the retract valve bore  136  further includes first and second auxiliary retract valve control pressure ports  904  and  905 . The addition of control pressure ports  902 ,  903 , 904  and  905  makes the extend and retract valves  102  and  104  operate as “master” extend and retract valves, respectively, which in turn control the position of “slave” extend and retract valves  502  and  504 , respectively. The actuator  106  controls the position of master extend and retract valves  102  and  104 . 
     As illustrated in  FIGS. 9-11 , the first and second auxiliary extend valve control pressure ports  902 ,  903  are both in continuous fluid communication with the second extend valve control pressure port  522 , regardless of the position of the extend poppet valve  112 . When the extend poppet valve  112  is in its closed position, as depicted in  FIGS. 9 and 11 , the first auxiliary extend valve control pressure port  902  is in fluid communication with the extend valve spring chamber  131 , and the second auxiliary extend valve control pressure port  903  is in fluid communication with the extend valve return pressure port  126  and extend valve spring chamber  131 . As illustrated in  FIG. 10 , when the extend poppet valve  112  is in its open position, the first and second auxiliary extend valve control pressure ports  902 ,  903  are in fluid communication with the extend valve inlet and outlet ports  118 ,  122 , and are fluidly isolated from the extend valve spring chamber  131 . 
     As  FIGS. 9-11  also depict, the first and second auxiliary retract valve control pressure ports  904 ,  905  are both in continuous fluid communication with the second retract valve control pressure port  542 , regardless of the position of the retract poppet valve  132 . When the retract poppet valve  132  is in its closed position, as depicted in  FIGS. 9 and 10 , the first auxiliary retract valve control pressure port  904  is in fluid communication with the retract valve spring chamber  133 , and the second auxiliary retract valve control pressure port  905  is in fluid communication with the retract valve return pressure port  146  and the retract valve spring chamber  133 . As illustrated in  FIG. 11 , when the retract poppet valve  112  is in its open position, the first and second auxiliary retract valve control pressure ports  904 ,  905  are in fluid communication with the retract valve inlet and outlet ports  138 ,  142 , and are fluidly isolated from the retract valve spring chamber  133 . 
     The system  900  depicted in  FIGS. 9-11  operates substantially identical to the system  500  depicted in  FIGS. 5-8 , thus a detailed description thereof will not be provided. It is noted, however, that the configurations of the first and second auxiliary extend valve control pressure ports  902 ,  903 , and the first and second auxiliary retract valve control pressure ports  904 ,  905  limits control pressure flow (PC 1 , PC 2 ) to just one of the poppets when the actuator  106  is commanded to the extend position or the retract position. More specifically, in the extend position, control pressure flow (PC 2 ) is limited to the master extend valve  102 , and in the retract position, control pressure flow (PC 1 ) is limited to the master retract valve  104 . This has the advantage of limiting the amount of control pressure flow (PC 1 , PC 2 ) required to actuate the poppet valves  112 ,  132 , which minimizes quiescent servo flow usage. It also allows the use of larger poppet valves that would require higher control pressure flow (PC 1 , PC 2 ). It is further seen that the extend valve poppet  112  and the retract valve poppet  132  are contoured, near their respective seating surfaces, to allow this control pressure flow when the poppet valves  112 ,  132  are moved between the open and closed positions. 
     Each of the (EHPV) device control systems  100 ,  500 ,  900  is in fluid communication with, and is used to control the position of, a device  110 . The device  110  being controlled may vary. For example, in the embodiments depicted in  FIGS. 1-11 , the device  110  is a hydraulically controlled actuator. In other embodiments, however, the device  110  may be, for example, a hydraulically controlled valve, such as a metering valve. 
     Regardless of the specific device  110 , it includes at least a device housing  164  that has an inner surface  166 , an outer surface  168 , and at least one actuation control pressure port  172 . With some embodiments, such as the ones depicted in  FIGS. 5 and 13  the device housing  164  includes two actuation control pressure ports  172  ( 172 - 1 ,  172 - 2 ), whereas in the embodiments depicted in  FIGS. 1 and 12 , the device housing  164  includes only one actuation control pressure port  172 . 
     Regardless of the number of actuation control pressure ports  172 , the inner surface  166  of the device housing  164  defines a device cavity  174 , within which a movable device  176  is at least partially disposed in and is movable within. The at least one actuation control pressure port  172  is in fluid communication with the extend valve outlet port  122  and the retract valve outlet port  142 , and the movable device  176  is movable in response to at least fluid pressure in the at least one actuation control pressure port  172 . 
     In this document, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Numerical ordinals such as “first,” “second,” “third,” etc. simply denote different singles of a plurality and do not imply any order or sequence unless specifically defined by the claim language. The sequence of the text in any of the claims does not imply that process steps must be performed in a temporal or logical order according to such sequence unless it is specifically defined by the language of the claim. The process steps may be interchanged in any order without departing from the scope of the invention as long as such an interchange does not contradict the claim language and is not logically nonsensical. 
     Furthermore, depending on the context, words such as “connect” or “coupled to” used in describing a relationship between different elements do not imply that a direct physical connection must be made between these elements. For example, two elements may be connected to each other physically, electronically, logically, or in any other manner, through one or more additional elements. 
     While at least one exemplary embodiment has been presented in the foregoing detailed description of the invention, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment of the invention. It being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set forth in the appended claims.