Constant current regulator

Abstract

The system is designed to compensate for flow disturbances when changing the flow rate in the system. The system includes a flow source device (12) having an inlet and an outlet. The inlet is configured to receive a fluid at a first pressure, and the outlet is configured to output a fluid at a second pressure higher than the first pressure. The system also includes a fluid control device (20) having an inlet port (30) and a discharge port (34). The inlet port of the fluid control device is configured to receive the flow from the outlet of the flow source device. In addition, the system includes a constant flow regulator (68) configured to provide a leakage flow to a discharge output (69). The constant flow regulator is configured to reduce the leakage flow in response to the discharge port of the fluid control device.

Description

Field of the Invention

[0001] The present invention relates generally to fluid flow systems and, more particularly, to fluid flow systems that provide an adjustable leakage path to eliminate disturbances associated with the rotation of an actuator. Background Art

[0002] To control a variable flow device, an electro-hydraulic servo valve (EHSV) is typically used to control the flow through the variable flow device. For example, the variable flow device can be a variable pump and the EHSV can mechanically position a variable pumping member to increase or decrease the flow. In such a system, the EHSV typically uses high-pressure fluid as the hydraulic fluid on the outlet side of the variable flow device to generate the mechanical actuation for positioning the variable pumping member. This form of actuation creates a rotational flow in the EHSV that causes large disturbances in the outlet flow of the variable flow device.

[0003] One prior attempt to solve this problem is known from U.S. Patent No. 6,102,001, filed Dec. 4, 1998 and issued Aug. 15, 2000, the entire contents of which are incorporated herein by reference. In the '001 patent, a controlled leakage is provided from the outlet of the variable flow device to the inlet side of the variable flow device through the EHSV. The leakage flow helps to compensate to some extent for the rotational flow of the EHSV. However, the compensation provided by the controlled leakage in the '001 patent is fixed and cannot be adjusted for differences in EHSV actuator speed (e.g., caused by friction) or for load variations in the variable flow device.

[0004] In view of the foregoing, the applicant has found a need in the art for a way to provide adjustable compensation for the rotational flow of an EHSV actuator to minimize fluid disturbances on the outlet side of the variable flow device. Summary of the Invention

[0005] Embodiments of the presently disclosed invention solve the foregoing problems and problems associated with traditional variable flow systems. In particular, embodiments of the presently disclosed flow systems utilize a pressure regulator to set a relatively constant flow rate across an adjustable orifice such that any swivel flow that moves an EHSV actuator is compensated for by closing the regulator and reducing its leakage, thereby maintaining a constant flow rate across the orifice and thus maintaining a constant flow rate of the pumping unit. The only input for the compensation provided by the pressure regulator is the actual swivel flow from the EHSV, making it insensitive to any other changes or perturbations in the system. Since the only input to the compensating pressure regulator is the swivel flow providing the compensation, the likelihood of errors due to other system factors is greatly reduced or eliminated entirely. Additionally, the orifice allows the system to be adjustable only for the swivel flow that needs to be compensated, thereby limiting the amount of additional leakage in the system. These and other advantages of the present invention, as well as additional inventive features, will become apparent from the description of the present invention provided herein.

[0006] According to one aspect, embodiments of the present disclosure provide a system designed to compensate for flow perturbations associated with varying flow rates in the system. In an embodiment, the system includes a flow source device having an inlet and an outlet. The inlet is configured to receive fluid at a first pressure, and the outlet is configured to output fluid at a second pressure that is higher than the first pressure. The system further includes a fluid control device having an inlet port and a drain port. The inlet port of the fluid control device is configured to receive flow from the outlet of the flow source device. Additionally, the system includes a constant flow regulator configured to provide a leakage flow to a drain output. The constant flow regulator is configured to reduce the leakage flow in response to the drain port of the fluid control device.

[0007] In more than one embodiment of the system, the constant flow regulator includes a pressure regulating valve (PRV). Additionally, the PRV includes a PRV inlet in fluid communication with the outlet of the fluid source device, and a PRV outlet in fluid communication with a first fluid line extending from the drain port of the fluid control device. Additionally, the constant flow regulator includes a restricting device in a second fluid line downstream of the PRV outlet and the first fluid line.

[0008] In more than one embodiment of the system, the system includes a brake actuated by the fluid control device, an electro-hydraulic servo valve (EHSV), and the electro-hydraulic servo valve (EHSV) uses fluid from the flow source device to actuate the actuator.

[0009] In one or more embodiments of the system, the EHSV includes a valve body that defines a valve bore, the inlet port, the discharge port, a first working port, and a second working port. The EHSV further includes a valve member disposed within the valve bore. The valve member is configured to translate within the valve bore to provide fluid communication between the inlet port and the first working port and between the second working port and the discharge port, or between the first working port and the discharge port and between the inlet port and the second working port. Additionally, the fluid flow from the inlet port actuates the actuator in a first direction through the first working port, and the fluid flow from the inlet port actuates the actuator piston in a second direction opposite to the first direction through the second working port.

[0010] In one or more embodiments of the system, the system includes a position sensor configured to detect movement of the actuator.

[0011] In one or more embodiments of the system, the actuator is a linear actuator.

[0012] In yet another embodiment of the system, the actuator is a rotary actuator.

[0013] In one or more embodiments of the system, the actuator is disposed within a housing. The housing further includes a first chamber coupled to the first working port and a second chamber coupled to the second working port.

[0014] In one or more embodiments of the system, the constant flow regulator is configured to reduce the leakage flow rate in proportion to the fluid flow rate from the first working port or the second working port to the discharge port.

[0015] In one or more embodiments of the system, the fluid control device is driven by a stepper motor, a direct drive motor, or a hydromechanical pilot valve.

[0016] In one or more embodiments of the system, the flow source device includes a variable pump.

[0017] In one or more embodiments of the system, the variable pump is a vane pump.

[0018] In yet another embodiment of the system, the variable pump is a piston pump.

[0019] In one or more embodiments of the system, the flow source device is a fuel metering system.

[0020] According to another aspect, embodiments of the present disclosure provide a method for compensating for flow disturbances associated with varying flow rates in a fluid flow system. In an embodiment of the method, fluid at a first pressure is received at an inlet of a flow source device. Fluid at a second pressure higher than the first pressure is output from an outlet of the flow source device. A portion of the fluid at the second pressure is received through an inlet port of a fluid control device to actuate an actuator. A leakage flow is provided to a discharge outlet by a constant flow regulator. The constant flow regulator is configured to reduce the leakage flow in response to a discharge flow from a discharge port of the fluid control device when the actuator is actuated.

[0021] In one or more embodiments of the method, the constant flow regulator includes a pressure regulating valve (PRV) and a restricting device. The leakage flow from a PRV inlet is provided through a PRV outlet, the PRV inlet being in fluid communication with the outlet of the flow source device, and the PRV outlet being in fluid communication with a first fluid line extending from the discharge port of the fluid control device. Additionally, the flow from the PRV outlet and the discharge port of the fluid control device is restricted.

[0022] In one or more embodiments of the method, the fluid control device is electrohydraulically actuated and uses a portion of the fluid passing through the inlet port of the fluid control device to move the actuator.

[0023] In one or more embodiments of the method, the fluid control device includes a valve body that defines a valve orifice, the inlet port, the discharge port, a first working port, and a second working port. The fluid control device further includes a valve member disposed within the valve orifice. The valve member is translated within the valve orifice to provide fluid communication between the inlet port and the first working port and between the second working port and the discharge port, or between the first working port and the discharge port and between the inlet port and the second working port. Additionally, the actuator is moved in a first direction when fluid flows from the inlet port through the first working port, or in a second direction when fluid flows from the inlet port through the second working port.

[0024] In one or more embodiments of the method, the leakage flow is reduced by the constant flow regulator in proportion to the fluid flow from the first working port to the discharge port or from the second working port to the discharge port.

[0025] In one or more embodiments of the method, the actuator is linked to the flow source device and moves a flow control member of the flow source device in response to movement of the actuator.

[0026] When combined with the accompanying drawings, other aspects, objects, and advantages of the present invention will become more apparent from the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The drawings incorporated in and forming a part of this patent specification illustrate several aspects of the invention and, together with the description, serve to explain the principles of the invention. In the drawings:

[0028] Figure 1 is a schematic depiction of a variable flow rate system according to an exemplary embodiment;

[0029] Figure 2 is a graph showing perturbations in the output flow rate due to the rotational flow through the actuator valve for the presently disclosed variable flow rate system according to an exemplary embodiment, and for a conventional variable flow rate system; and

[0030] Figure 3 depicts a general schematic diagram of a variable flow rate system according to an exemplary embodiment.

[0031] Although the invention will be described in connection with certain preferred embodiments, it is not intended to be limited to those embodiments. On the contrary, it is intended to cover all alternatives, modifications, and equivalents included within the spirit and scope of the invention as defined by the appended claims. DETAILED DESCRIPTION

[0032] Figure 1 An embodiment of a flow rate system 10 is depicted, such as a fuel control system (e.g., for an aircraft). The flow rate system 10 includes a flow source device 12 that receives a low-pressure fluid P on a first fuel line 14 B and the flow source device 12 injects a high-pressure fluid P on a second line 16 S . The high-pressure fluid P S is provided to an outlet 18 through which the fluid is provided to downstream processing, such as a fuel manifold and a combustion chamber (not shown) of an exemplary embodiment of a fuel system. In such an embodiment, the pressure P of the fluid may be set by a nozzle of the fuel manifold that injects fuel into the combustion chamber S . In an embodiment, the downstream processing may require a fluid with a variable pressure, and the flow source device 12 regulates the flow rate of the fluid.

[0033] Additionally, the high-pressure fluid P injected from the flow source device 12 Sis utilized by a fluid control device 20 depicted as an electro-hydraulic servo valve (ENSV). Although the fluid control device 20 is depicted as electro-hydraulically actuated, the fluid control device 20 could instead be hydraulically actuated or hydromechanically actuated. In other possibilities, for example, in an embodiment, the fluid control device 20 could be actuated by a stepper motor, a direct drive motor, or a hydromechanical pilot valve. The fluid control device 20 includes an actuator control valve 22 having a valve member 24 disposed within a valve bore 26 of a valve body 28, such as a spool valve. The valve body 26 defines an inlet port 30 and a drain port 34 of the valve bore 26. The valve body 26 defines a first working port 36 and a second working port 38. The inlet port 30 is in fluid communication with a high-pressure fluid P S through a third line 39. The position of the valve member 24 within the valve bore 26 controls the flow of the high-pressure fluid P S from the inlet port 30 to one of the respective first or second working ports 36, 38, and from the other of the working ports 36, 38 to the drain port 34.

[0034] More specifically, the actuator control valve 22 includes a first nozzle 40 and a second nozzle 42 that receive the high-pressure fluid P S from the third line 39 through the inlet port 30 and through respective restriction devices 43, respectively. The nozzles 40, 42 inject the high-pressure fluid into an actuator control valve chamber 44. Disposed within the valve chamber 44 is a flapper 46 connected to an armature 48 of a torque motor 50. The torque motor 50 can be actuated to tilt the armature 48, which in turn tilts the flapper 46 toward one of the nozzles 40 and 42. If the flapper 46 tilts toward the first nozzle 40, the valve member 24 shifts to the right (relative to the orientation depicted in Figure 1 ), thereby opening the flow between the first working port 36 and the drain port 34 and between the inlet port 30 and the second working port 38. This fluid acts on an actuator 51 depicted as a piston 52. In more than one embodiment, the actuator 51 is a linear actuator, such as the depicted piston 52, while in more than one other embodiment, the actuator 51 is a rotary actuator, such as a rotary vane actuator.

[0035] In the depicted embodiment, the piston 52 is disposed within a housing 54 having a first chamber 56 disposed on one side of the piston 52 and a second chamber 58 disposed on the opposite side of the piston 52. The first working port 36 is fluidly coupled to the first chamber 56 through a fourth line 60, and the second working port 38 is fluidly coupled to the second chamber 58 through a fifth line 62. For example, when the high-pressure fluid P S is provided from the inlet port 30 to the second working port 38, the fluid flows into the second chamber 58 through the fifth line 62, forcing the piston 52 to move to the left (relative toFigure 1 (the orientation depicted in). The movement of the piston 52 reduces the volume of the first chamber 56, forcing fluid to flow through the fourth pipeline 60 into the first working port 36 and out of the discharge port 34. The movement of the piston 52 is sensed by a position sensor of the linear actuator, which is depicted as a linear variable differential transformer (LVDT) 64. Additionally, the baffle 46 is connected to a feedback spring 66, which is connected to the valve member 24 and senses the position of the valve member 24.

[0036] When the torque motor 50 tilts the armature 48 such that the baffle 46 blocks the second nozzle 42, the valve member 24 moves leftward within the valve orifice 26. This opens the fluid communication between the inlet port 30 and the first working port 36. Fluid flows from the first working port 36 through the fourth pipeline 60 to the first chamber 56, pushing the piston 52 to move rightward within the valve housing 54 (relative to Figure 1 (the orientation depicted in). Meanwhile, the fluid communication between the second working port 38 and the discharge port 34 is opened, allowing fluid to flow out of the discharge port 34 from the second chamber 58 through the fifth pipeline 62. When the baffle 46 is located in the middle of the first nozzle 40 and the second nozzle 42, the two nozzles 40, 42 inject fluid into the actuator control valve chamber 44, and the fluid flows out through the discharge port 34. The fluid flowing into the valve orifice 26 from the inlet port 30 and the working ports 36, 38 is blocked. Therefore, in this configuration, the valve member 24 and the piston 52 are in the centered position or the zero position.

[0037] Using the LVDT 64 and the feedback spring 66, the state of the actuator control valve 22 can be determined and controlled, thereby actuating the actuator 51. In such an embodiment, the actuator 51 can be used to position the flight control surface of an aircraft. In other embodiments, the actuator control valve 22 and the actuator 51 can be used to regulate the flow source device 12. In such an embodiment, the actuator 51 is mechanically, hydraulically or pneumatically linked to the flow source device 12. For example, in the depicted embodiment, if the flow source device 12 is a variable pump, the piston 52 can move the rotor or the surrounding cam ring (for vane pumps) or can change the angle of the swash plate (for piston pumps) to increase or decrease the flow provided by the variable pump flow source device 12. In more than one exemplary embodiment, the piston 52 is electrically sensed and used to position the flow source device 12. For example, the LVDT 64 can control the flow output through a controller to adjust the position and / or the pump flow.

[0038] Since the fluid control device 20 uses high-pressure fluid P SOperation, so the actuation of the fluid control device 20 takes away the fluid discharged by the flow source device 12 on the second pipeline 16, resulting in an instantaneous reduction in the flow output 18 for downstream processing. To counteract this output reduction, the flow system 10 includes a constant flow regulator 68, which provides a leakage path from the flow source device 12 to the discharge output 69, such as the low-pressure side of the flow source device 12, a fluid reservoir (e.g., a fuel tank), or a low-pressure oil sump.

[0039] The constant flow regulator 68 includes a pressure regulating valve 70 and a restricting device 72. The pressure regulating valve 70 includes a valve member 74 that translates within a housing 76. One side of the valve member 74 is a valve chamber 78 and a biasing member, such as a spring 80. The spring 80 biases the valve member 74 toward a closed position to control the fluid flow through an outlet 81. The other side of the valve member 74 is a first inlet 82, which is configured to receive high-pressure fluid P from the second pipeline 16 on the output side of the flow source device 12. S The high-pressure fluid P S bypasses the valve member 74 and goes to the outlet 81 to provide a constant leakage flow. In addition, the pressure regulating valve 70 includes a second inlet 84 that is in fluid communication with the discharge port 34 of the fluid control device 20 via a sixth pipeline 86. The second inlet 84 is also in fluid communication with a seventh pipeline 88. Arranged in the seventh pipeline 88 is the restricting device 72 leading to the discharge output 69.

[0040] As discussed in the background section, when the actuator control valve 22 of the fluid control device 20 rotates, the fluid from one of the working ports 36, 38 flows into the discharge port 34, and the high-pressure fluid P from the inlet port 30 S actuates the piston 52 through the other of the working ports 36, 38. Using the high-pressure fluid P in this way S may cause disturbances in the output flow of the flow source device 12, such as in the case of a conventional system. However, here, the discharge flow or rotational flow of the fluid control device 20 is closely related to the output of the pressure regulating valve 70. When the rotational flow through the sixth pipeline 86 saturates the flow through the restricting device 72, the pressure regulating valve 70 senses an increase in pressure in the seventh pipeline 88. In response, the pressure regulating valve 70 closes its discharge port 81 and reduces the flow from the second pipeline 16 through the inlet 82 by an amount equal to the rotational flow of the fluid control device 20. The discharge port 81 is also connected to the discharge output 69. Therefore, the reduced leakage flow through the port 81 offsets the rotational flow, so that the net output of the flow source device 12 remains substantially consistent with the output 18 for downstream processing.

[0041] Figure 2A graph of the change in flow velocity between the output 18 of the flow system 10 according to the present disclosure and the outlet of the flow source device 12 with respect to a conventional flow system is provided. In particular, the y-axis of the graph represents the change in flow velocity at the output 18 (instantaneous flow velocity - initial flow velocity) minus the change in flow velocity at the outlet of the flow source device 12 (instantaneous flow velocity - initial flow velocity). A value of "0" means that the change in flow velocity at each location matches. In the graph, the x-axis represents time. At time T1, the fluid control device 20 is actuated in a first direction by supplying current to the torque motor 50, and at time T2, the fluid control device 20 is actuated in a second direction by supplying the opposite current to the torque motor 50.

[0042] As can be seen from the graph, the first actuation of the fluid control device at time T1 results in a significant change in the flow velocity between the outlet of the flow control device and the output of the conventional flow system. In particular, the negative value of the change in flow velocity indicates that the change in flow velocity at the outlet of the flow source device is much greater than the change in flow velocity at the output. The lower change in flow velocity at the output is attributed to the swirl flow associated with the actuation of the actuator control valve, preventing the output from experiencing the same change in flow velocity. After some time, as the actuator reaches its commanded position, the swirl flow from the fluid control device ends, and thereafter, the change in flow velocity between the output and the outlet of the flow control device equalizes.

[0043] At time T2, the fluid control device is actuated again (in the opposite direction), and this actuation generates swirl flow through the actuator, which again creates a significant perturbation in the flow at the output. After the swirl flow ends, the change in flow velocity between the output and the outlet of the flow control system equalizes again. Any further actuation of the conventional flow system will cause a similar perturbation in the flow velocity of the flow system.

[0044] In contrast, Figure 2The flow rate change amplitude of the flow system 10 of the present disclosure is much smaller. In particular, at time T1, the fluid control device 20 is actuated to generate a swirling flow. However, compared with the traditional flow system, since there is already a leakage flow in the system, the swirling flow is compensated. That is, the swirling flow caused by the actuation of the fluid control device 20 replaces the continuous leakage flow established in the system. The constant flow regulator 68 provides a continuous leakage path, and the pressure regulating valve 70 senses the swirling flow from the fluid control device 20 and closes or weakens the leakage flow from the second pipeline 16 in response to the sensed swirling flow. In particular, at the first actuation of the actuator control valve at time T1, the change in the flow rate between the output 18 and the outlet of the flow source device 12 is positive, meaning that due mainly to the compressibility effect of the fluid (although the system size and total compressibility will affect the amplitude of this phenomenon), the change in the flow rate at the output 18 is actually greater than the change in the flow rate at the outlet of the flow source device 12. However, even though the flow rate change increases, the amplitude of the change is significantly smaller than that of the traditional flow control system. Similarly, when the fluid control device 20 is actuated in the reverse direction at time T2, the flow system 10 of the present disclosure experiences a flow rate change with an amplitude much smaller than that of the traditional system. In particular, the absolute value of the flow rate change amplitude is 50% or less, preferably 30% or less, more preferably 25% or less, and most preferably 20% or less of the absolute value of the flow rate change amplitude of the traditional system.

[0045] Although the above discussion relates to an exemplary implementation of the flow control system 10, the present disclosure is more broadly applicable to other types of flow control systems or other aspects within a flow control system. Figure 3 A schematic overview of the flow control concept is provided. As can be seen in Figure 3 the flow source device 12 receives an input flow of fluid at a first pressure P B and outputs a fluid flow at a second pressure P S higher than the first pressure. In various embodiments, the flow source device 12 is a pump, and in other possibilities, such as a variable pump (e.g., a rotary vane pump or a piston pump), or a fuel metering valve.

[0046] The fluid control device 20 utilizes the flow from the flow source device 12 to the flow control actuator 51. In an embodiment, the fluid control device 20 is driven electrohydraulically, electromechanically, pneumatically, hydraulically, or mechanically to position the actuator. In an embodiment, the fluid control device 20 includes an actuator control valve 22 that translates, for example, using a stepper motor, a direct drive motor, or a hydromechanical pilot valve. For example, the actuator control valve 22 can be translated by a stepper motor having a drive shaft that is mechanically connected to a cam (e.g., instead of Figure 1The baffle 46) shown positions the cam directly relative to the nozzles 40, 42 of the actuator control valve 22 as Figure 1 shown.

[0047] As described above, the flow disturbances caused by the actuation of the fluid control device 20 are limited by the constant flow regulator 68 located at the outlet of the fluid control device 20. The constant flow regulator 68 provides a leakage flow to a drain output, such as the inlet of the flow source device 12, a fluid reserve tank (e.g., a fuel tank), or another low-pressure oil sump. As described above, regardless of the state of the fluid control device 20, there is a leakage flow through the constant flow regulator 68 (i.e., there is always at least some leakage flow through the constant flow regulator 68). Before the actuation of the fluid control rotor 20, the leakage flow is provided from the outlet of the flow source device 12 through the constant flow regulator 68. When the fluid control device 20 is actuated, the rotational flow associated with the actuation of the fluid control device 20 replaces the leakage flow at the outlet of the flow source device 12. In this way, the reduction in the leakage flow from the outlet of the flow source device 12 compensates for the fluid from the outlet of the flow source device 12 used to actuate the fluid control device 20.

[0048] All references cited herein, including published publications, patent applications, and patents, are incorporated herein by reference to the extent that each reference is specifically and individually indicated to be incorporated by reference in its entirety and set forth herein.

[0049] The use of the terms "a" (indefinite article "a" or "an") and "the" and similar nouns in the context of describing the present invention (especially in the context of the appended claims) is construed to cover the singular and plural, unless otherwise indicated herein or clearly contradicted by the context. The terms "comprising" (comprising or including), "having", and "containing" are construed as open-ended terms (i.e., meaning "including, but not limited to"), unless otherwise noted. The recitation of numerical ranges herein is merely intended to be a shorthand reference to each individual numerical value falling within the recited range, unless otherwise indicated herein, and each individual numerical value is incorporated into the specification as if it were recited individually herein. All methods described herein can be performed in any suitable order, unless otherwise indicated herein or clearly contradicted by the context. The use of any and all examples, or exemplary language (e.g., "such as") provided herein is merely intended to better illustrate the invention and is not intended to limit the scope of the invention, unless otherwise required. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.

[0050] Preferred embodiments of the invention are described herein, including the best mode known to the inventors for practicing the invention. Variations of these preferred embodiments will become apparent to those skilled in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, as permitted by applicable law, the invention includes all modifications and equivalents of the subject matter recited in the following claims. Moreover, the invention includes any combination of the above elements in all possible variations thereof, unless otherwise stated herein or clearly precluded by context.

Claims

1. A system configured to compensate for flow disturbances associated with varying flow rates, comprising: A flow source device having an inlet and an outlet, the inlet configured to receive fluid at a first pressure, and the outlet configured to output fluid at a second pressure higher than the first pressure; A fluid control device having an inlet port and a discharge port, the inlet port of the fluid control device configured to receive flow from the outlet of the flow source device; A constant flow regulator configured to provide a leakage flow to a discharge output; wherein the constant flow regulator is configured to reduce the leakage flow in response to an increase in the flow through the discharge port of the fluid control device.

2. The system according to claim 1, wherein the fluid control device is driven by a stepper motor, a direct drive motor, or a hydraulic mechanical pilot valve.

3. The system according to claim 1, wherein the flow source device includes a variable pump.

4. The system according to claim 3, wherein the variable pump is a vane pump.

5. The system according to claim 3, wherein the variable pump is a piston pump.

6. The system according to claim 1, wherein the flow source device is a fuel metering system.

7. A system configured to compensate for flow disturbances associated with varying flow rates, comprising: A flow source device having an inlet and an outlet, the inlet configured to receive fluid at a first pressure, and the outlet configured to output fluid at a second pressure higher than the first pressure; A fluid control device having an inlet port and a discharge port, the inlet port of the fluid control device configured to receive flow from the outlet of the flow source device; A constant flow regulator configured to provide a leakage flow to a discharge output; wherein the constant flow regulator is configured to reduce the leakage flow in response to an increase in the flow through the discharge port of the fluid control device; and wherein the constant flow regulator includes a pressure regulating valve and a restricting device, wherein the pressure regulating valve includes a pressure regulating valve inlet in fluid communication with the outlet of the flow source device, and a pressure regulating valve outlet in fluid communication with a first fluid line extending from the discharge port of the fluid control device, and wherein the restricting device is located in the second fluid line downstream of the pressure regulating valve outlet and the first fluid line.

8. The system according to claim 7, further comprising an actuator, wherein the fluid control device is an electro-hydraulic servo valve, and wherein the electro-hydraulic servo valve uses fluid from the flow source device to actuate the actuator.

9. The system according to claim 8, wherein the electro-hydraulic servo valve comprises: A valve body defining a valve orifice, the inlet port, the discharge port, a first working port, and a second working port; A valve member disposed within the valve orifice; wherein the valve member translates within the valve bore to provide (i) fluid communication between the inlet port and the first working port and between the second working port and the discharge port or (ii) fluid communication between the first working port and the discharge port and between the inlet port and the second working port; wherein a fluid flow from the inlet port actuates the actuator in a first direction through the first working port, and a fluid flow from the inlet port actuates the actuator piston in a second direction opposite to the first direction through the second working port.

10. The system according to claim 8, further comprising a position sensor configured to detect movement of the actuator.

11. The system according to claim 8, wherein the actuator is a linear actuator.

12. The system according to claim 8, wherein the actuator is a rotary actuator.

13. The system according to claim 9, wherein the actuator is disposed within a housing having a first chamber coupled to the first working port and a second chamber coupled to the second working port.

14. The system according to claim 9, wherein the constant flow regulator reduces the leakage flow in proportion to the fluid flow from the first working port or the second working port to the discharge port.

15. A method of compensating for flow perturbations associated with varying flow rates, comprising: receiving fluid at a first pressure at an inlet of a flow source device, outputting fluid at a second pressure higher than the first pressure from an outlet of the flow source device; receiving a portion of the fluid at the second pressure through an inlet port of a fluid control device to actuate an actuator; providing a leakage flow to a discharge output through a constant flow regulator, wherein the constant flow regulator is configured to reduce the leakage flow in response to a discharge flow from a discharge port of the fluid control device when actuating the actuator.

16. The method according to claim 15, wherein the constant flow regulator includes a pressure regulating valve and a restricting device, and wherein the method further comprises: providing the leakage flow from an inlet of the pressure regulating valve through an outlet of the pressure regulating valve, the inlet of the pressure regulating valve being in fluid communication with the outlet of the flow source device, the outlet of the pressure regulating valve being in fluid communication with a first fluid line extending from the outlet port of the fluid control device, and restricting the flow from the outlet of the pressure regulating valve and the discharge port of the fluid control device.

17. The method according to claim 16, wherein the fluid control device is electrohydraulically actuated, and wherein the method further comprises: using a portion of the fluid passing through the inlet port of the fluid control device to move the actuator.

18. The method according to claim 17, wherein the fluid control device comprises: a valve body defining a valve bore, the inlet port, the discharge port, a first working port, and a second working port; and a valve member disposed within the valve bore; wherein the method further comprises: Translate the valve member within the valve bore to provide (i) fluid communication between the inlet port and the first working port and between the second working port and the discharge port, or (ii) fluid communication between the first working port and the discharge port and between the inlet port and the second working port; and Move the actuator in a first direction when fluid flows from the inlet port through the first working port, or move the actuator in a second direction when fluid flows from the inlet port through the second working port.

19. The method according to claim 18, further comprising reducing the leakage flow rate in proportion to the fluid flow rate from the first working port to the discharge port or from the second working port to the discharge port through the constant flow regulator.

20. The method according to claim 17, wherein the actuator is linked to the flow source device, and wherein the method further comprises moving a flow control member of the flow source device in response to movement of the actuator.

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