Hydraulic power pump control

Abstract

A hydraulic power unit includes a reservoir containing hydraulic fluid, a primary output, a pressure sensor, at least one active valve hydraulic pump, and at least one passive valve hydraulic pump. The primary flow of hydraulic fluid is discharged through the primary output. The pressure sensor includes a pressure signal indicative of a pressure of the primary flow. Each active valve hydraulic pump is configured to drive a first flow portion of the primary flow from the reservoir to the primary output when the pressure signal is below a first pressure setpoint. Each passive valve hydraulic pump is configured to drive a second flow portion of the primary flow from the reservoir to the primary output when the pressure signal is below a second pressure setpoint.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of priority to U.S. Provisional Patent Application No. 63 / 517,180, filed on August 2, 2023, entitled “Hydraulic Power Generation Pump Control,” the contents of which are incorporated herein by reference. Technical Field

[0003] Embodiments of the present disclosure relate generally to hydraulic power generation, and more particularly to hydraulic power generation using two different types of hydraulic pumps. Background Art

[0004] Dynamic testing systems, such as those developed by MTS Systems, include test stations that perform various tests by applying loads and displacements to a test object using hydraulic actuators. Test stations may include, for example, a vehicle test station that applies simulated driving conditions to a moving vehicle, or a building test station that applies simulated seismic activity to a building.

[0005] The hydraulic actuators of the test station are driven by a flow of hydraulic fluid generated by a hydraulic power unit. Conventional hydraulic power units include multiple passive valve hydraulic pumps with variable displacement. Such passive valve hydraulic pumps include, for example, hydraulic piston pumps having multiple piston pumps (e.g., piston and cylinder assemblies) with adjustable working volumes for varying the flow of hydraulic fluid discharged. Passive (e.g., pressure-actuated) valves are used to control the flow of hydraulic fluid into and out of the working volume. A common type of passive valve hydraulic pump used in a hydraulic power unit is a variable displacement axial piston pump that utilizes a wave plate to vary the working volume of the piston pump.

[0006] While passive valve hydraulic pumps with variable displacement can be effective in efficiently providing large volumes of hydraulic fluid flow, they are generally unable to respond quickly to changes in fluid flow demand. Summary of the invention

[0007] Embodiments of the present disclosure relate to hydraulic power generation for a dynamic test system and include a hydraulic power unit and method of operating a hydraulic power unit, a hydraulic power system and method of operating a hydraulic power system.

[0008] One embodiment of a hydraulic power unit (HPU) includes a reservoir containing hydraulic fluid, a main output, a pressure sensor, at least one active valve hydraulic pump, and at least one passive valve hydraulic pump. The housing contains the reservoir, at least one active hydraulic pump, and at least one passive hydraulic pump. The main flow of hydraulic fluid is discharged through the main output. The pressure sensor includes a pressure signal indicating the pressure of the main flow. Each active valve hydraulic pump is configured to drive a first flow portion of the main flow from the reservoir to the main output when the pressure signal is below a first pressure set point. Each passive valve hydraulic pump is configured to drive a second flow portion of the main flow from the reservoir to the main output when the pressure signal is below a second pressure set point.

[0009] In some embodiments of the HPU, the first pressure set point is less than the second pressure set point, or the first pressure set point is greater than the second pressure set point.

[0010] In some embodiments of the HPU, the first pressure set point is approximately 1-5% less than the second pressure set point.

[0011] In some embodiments of the HPU, the first pressure set point is approximately 1-5% greater than the second pressure set point.

[0012] In some embodiments of the HPU, the first pressure set point is equal to the second pressure set point.

[0013] In some embodiments, the hydraulic power unit includes at least one controller configured to set a first pressure set point and a second pressure set point.

[0014] In some embodiments of the HPU, the at least one passive valve hydraulic pump includes a plurality of passive valve hydraulic pumps.

[0015] In some embodiments of the HPU, the at least one active valve hydraulic pump includes a plurality of active valve hydraulic pumps.

[0016] In some embodiments of the HPU, the at least one active valve hydraulic pump includes a plurality of active valve hydraulic pumps.

[0017] In some embodiments of the HPU, each active valve hydraulic pump includes: a low-pressure port connected to a fluid reservoir; a high-pressure port connected to a main output; a plurality of piston pumps; a motor configured to drive a cyclic change in the working volume of each piston pump; a plurality of active valves, each of which corresponds to one of the piston pumps and is configured to set the piston pump to an activated state and a deactivated state, in which the cyclic change in the working volume drives a first flow portion of the hydraulic fluid from the working volume through the high-pressure port, and in which the deactivated state forms a fluid path between the working volume and the reservoir or the low-pressure port; and a pump controller configured to control each active valve to individually set the piston pump to an activated state or a deactivated state.

[0018] In some embodiments of the HPU, each passive valve hydraulic pump includes: a low pressure port connected to a fluid reservoir; a high pressure port connected to a main output; a plurality of piston pumps, each piston pump being configured to draw hydraulic fluid into an adjustable working volume through the low pressure port and drive a second flow portion of the hydraulic fluid from the adjustable working volume through the high pressure port; and a motor configured to drive a cyclic change in the adjustable working volume of each piston pump.

[0019] In one example of a method of operating a hydraulic power unit, when the pressure signal indicates that the pressure of the main flow is below a first pressure set point, one or more of the at least one active valve hydraulic pumps are used to drive a first flow portion of the main flow. When the pressure signal indicates that the pressure of the main flow is above the first pressure set point, the at least one active valve hydraulic pump is deactivated. When the pressure signal indicates that the pressure of the main flow is below a second pressure set point, one or more of the at least one passive valve hydraulic pumps are used to drive a second flow portion of the main flow. When the pressure signal indicates that the pressure of the main flow is above the second pressure set point, the at least one passive valve hydraulic pump is deactivated.

[0020] In some embodiments of the method, the first pressure set point is less than the second pressure set point, or the first pressure set point is greater than the second pressure set point.

[0021] In some embodiments of the method, the first pressure set point is approximately 1-5% less than the second pressure set point.

[0022] In some embodiments of the method, the first pressure set point is approximately 1-5% greater than the second pressure set point.

[0023] In some embodiments of the method, the first pressure set point is equal to the second pressure set point.

[0024] In some embodiments of the method, the at least one passive valve hydraulic pump includes a plurality of passive valve hydraulic pumps.

[0025] In some embodiments of the method, the at least one active valve hydraulic pump includes a plurality of active valve hydraulic pumps.

[0026] In some embodiments of the method, the at least one active valve hydraulic pump includes a plurality of active valve hydraulic pumps.

[0027] In some embodiments of the method, each active valve hydraulic pump includes: a low pressure port connected to a fluid reservoir; a high pressure port connected to a main output; a plurality of first piston pumps; a motor configured to drive a cyclic change in the working volume of each first piston pump; a plurality of active valves, each active valve configured to set one of the first piston pumps to an activated state and a deactivated state, in which the cyclic change in the working volume drives a portion of the first flow portion through the high pressure port in the activated state and forms a fluid path between the working volume and the reservoir or the low pressure port in the deactivated state; and a pump controller configured to control each active valve to individually set the first piston pump to an activated state or a deactivated state; and each passive valve hydraulic pump includes: a low-pressure port connected to a fluid reservoir; a high-pressure port connected to a main output; a plurality of second piston pumps, each second piston pump being configured to draw hydraulic fluid into an adjustable working volume through the low-pressure port and drive a portion of a second flow portion of the hydraulic fluid from the adjustable working volume through the high-pressure port; and a motor configured to drive a cyclic change in the adjustable working volume of each second piston pump.

[0028] One embodiment of a hydraulic power system includes at least one first hydraulic power unit, at least one second hydraulic power unit, and a flow concentrator. Each first hydraulic power unit includes: a first reservoir containing hydraulic fluid; a first main output through which a first main flow of hydraulic fluid is discharged; a first pressure sensor having a first pressure signal indicating a first pressure of the first main flow; and at least one active valve hydraulic pump configured to drive a flow portion of the first main flow from the first reservoir to the first main output when the first pressure signal indicates that the first pressure is below a first pressure set point. Each second hydraulic power unit includes: a second reservoir containing hydraulic fluid; a second main output through which a second main flow of hydraulic fluid is discharged; a second pressure sensor having a second pressure signal indicating a second pressure of the second main flow; and at least one passive valve hydraulic pump, each passive valve hydraulic pump configured to drive a flow portion of the second main flow from the second reservoir to the second main output when the second pressure signal indicates that the second pressure is below a second pressure set point. The flow concentrator is configured to combine the first main flow and the second main flow into a combined main flow.

[0029] In some embodiments of the system, the first pressure set point is less than the second pressure set point, or the first pressure set point is greater than the second pressure set point.

[0030] In some embodiments of the system, the first pressure set point is approximately 1-5% less than the second pressure set point.

[0031] In some embodiments of the system, the first pressure set point is approximately 1-5% greater than the second pressure set point.

[0032] In some embodiments of the system, the first pressure set point is equal to the second pressure set point.

[0033] In some embodiments, the system includes at least one controller configured to set a first pressure set point and a second pressure set point.

[0034] In some embodiments of the system, the at least one passive valve hydraulic pump includes a plurality of passive valve hydraulic pumps.

[0035] In some embodiments of the system, the at least one active valve hydraulic pump includes a plurality of active valve hydraulic pumps.

[0036] In some embodiments of the system, the at least one active valve hydraulic pump includes a plurality of active valve hydraulic pumps.

[0037] In some embodiments of the system, each active valve hydraulic pump includes: a low-pressure port connected to a fluid reservoir; a high-pressure port connected to a main output; a plurality of first piston pumps; a motor configured to drive a cyclic change in the working volume of each first piston pump; and a plurality of active valves, each of which is configured to set one of the first piston pumps to an activated state and a deactivated state, in which the cyclic change in the working volume drives a portion of the first main flow from the working volume through the high-pressure port, and in which the flow is formed between the working volume and the reservoir or the low-pressure port in the deactivated state. body path; and a pump controller configured to control each active valve to individually set the first piston pump to an activated state or a deactivated state; and each passive valve hydraulic pump includes: a low-pressure port connected to a fluid reservoir; a high-pressure port connected to a main output; a plurality of second piston pumps, each of which is configured to draw hydraulic fluid into an adjustable working volume through the low-pressure port and drive a portion of a second main flow from the adjustable working volume through the high-pressure port; and a motor configured to drive a cyclic change in the adjustable working volume of each second piston pump.

[0038] In some embodiments, the one or more pressure sensors are each replaced with a flow sensor having a flow signal indicative of the flow rate of the corresponding fluid flow rather than the pressure, and the pump is controlled based on the flow signal from the flow sensor.

[0039] This summary is provided to introduce selected concepts in a simplified form, which are further described in the detailed description below. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to help determine the scope of the claimed subject matter. The claimed subject matter is not limited to implementations that solve any or all of the disadvantages noted in the background technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 is a simplified diagram of an example of a dynamic testing system according to an embodiment of the present disclosure.

[0041] Figure 2 is a simplified diagram of an example of a hydraulic power unit according to an embodiment of the present disclosure.

[0042] Figure 3 is a simplified diagram of an example of a hydraulic power system according to an embodiment of the present disclosure.

[0043] Figure 4 is a simplified diagram of an example of a passive valve hydraulic pump according to an embodiment of the present disclosure.

[0044] Figure 5is a simplified side cross-sectional view of an example of a variable displacement axial pump according to an embodiment of the present disclosure.

[0045] Figure 6 is a simplified diagram of an example of an active valve hydraulic pump according to an embodiment of the present disclosure.

[0046] 7A to 7C is a diagram illustrating an embodiment according to the present disclosure Figure 6 Simplified diagram of the different operating modes of one of the piston pumps of an active valve hydraulic pump.

[0047] Figure 8 is a simplified diagram of a controller according to an embodiment of the present disclosure.

[0048] Fig. 9 is a chart illustrating an example operation of a hydraulic power unit according to an embodiment of the present disclosure.

[0049] Fig.10 is a chart illustrating an example operation of a hydraulic power unit according to an embodiment of the present disclosure.

[0050] Fig.11 is a flow chart illustrating an example of a method of operating a hydraulic power unit according to an embodiment of the present disclosure.

[0051] Fig.12 is a flow chart illustrating an example of a method of operating a hydraulic power system according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0052] Embodiments of the present disclosure will be described more fully below with reference to the accompanying drawings. Elements identified with the same or similar reference numerals refer to the same or similar elements. However, different embodiments of the present disclosure can be implemented in many different forms, and should not be interpreted as being limited to the embodiments set forth herein. On the contrary, these embodiments are provided so that the present disclosure will be thorough and complete, and the scope of the present disclosure will be fully conveyed to those skilled in the art.

[0053] Figure 1 1 is a simplified diagram of an example of a dynamic test system 100 according to an embodiment of the present disclosure. The test system 100 may include one or more test stations 102, each of which may be configured to perform a test or condition simulation by applying force and / or displacement to a test object 103 (e.g., a car, a building, etc.) using a hydraulic actuator 104.

[0054] Hydraulic actuators 104 are driven by hydraulic fluid flows 106 generated by one or more hydraulic power units (HPUs) 110. The combination of flows 106 may provide the desired flow required by test station 102.

[0055] The system 100 may also include one or more hydraulic power systems (HPS) 114. Each HPS 114 includes a combination of two or more of the HPUs 110, such as HPU 110A and HPU 110B. The hydraulic fluid flow 106 output by each HPU 110 is controlled to produce a desired combined hydraulic fluid flow, as discussed below.

[0056] The system 100 may include an accumulator 116 that stores pressurized hydraulic fluid received from the HPU 110 and / or the HPS 114. The accumulator 116 may discharge a flow 118 of hydraulic fluid that may be supplied to the test station 102.

[0057] In some embodiments, system 100 may include a distributor 120 that receives hydraulic fluid flow from HPU 110, HPS 114, and / or accumulator 116 and distributes the hydraulic fluid flow to test stations 102 as indicated by arrows 122. Other arrangements may also be used to form system 100.

[0058] The system 100 may be a closed system in which a flow of low pressure hydraulic fluid 124 used by the test station 102 , for example, is returned to the HPU 110 , such as through a hydraulic distribution system 120 .

[0059] The system controller 126 may be operable to control various aspects of the system 100 , including the functionality of the HPU 110 , the HPS 114 , valve assemblies (e.g., accumulator and / or distributor valve assemblies), and / or other aspects of the system 100 to supply the desired hydraulic fluid flow 122 to the test station 102 .

[0060] Figure 2 is a simplified diagram of an example of an HPU 110 according to an embodiment of the present disclosure. In some embodiments, each HPU 110 is configured to produce a main hydraulic fluid flow 106, which may have a flow rate of, for example, 50 gpm or more, such as up to about 200 gpm or more.

[0061] Each HPU 110 may include an HPU controller 128 that controls the operation of the HPU 110 to produce a desired hydraulic fluid flow 106. In some embodiments, the HPU 110 includes two or more pumps 130, each configured to drive a hydraulic fluid flow 132 that forms at least a portion of the main flow 106 that is discharged through a main output 133. Each pump 130 may take the form of a variable displacement hydraulic pump, such as an axial piston pump, a radial piston pump, a bent axis piston pump, a rotary vane pump, and / or other types of variable displacement hydraulic pumps suitable for use in the system 100, for example.

[0062] Each pump 130 includes an electric motor 134 for driving the pump 130, such as through a suitable gear arrangement. For example, the motor 134 can be a 45 kW or 60 horsepower motor. The HPU 110 can employ a cooling system (not shown) to cool the motor 134 and other components of the HPU 110.

[0063] In one embodiment, the pumps 130 of one or more HPUs 110 of the system 100 include one or more first pumps 130A of a first type and one or more second pumps 130B of a second type different from the first type. For example, the HPU 110 may include 1 to 5 pumps 130A and 1 to 5 pumps 130B, such as 1 to 2 pumps 130A and 2 to 5 pumps 130B. As discussed below, both the pumps 130A and 130B can complement each other to provide better performance than conventional HPUs 110 that utilize a single type of pump.

[0064] In one embodiment, each pump 130A is an active valve hydraulic pump having a variable displacement, and each pump 130B is a passive valve hydraulic pump having a variable displacement. Examples of pumps 130A and 130B are described in more detail below.

[0065] In some embodiments, the system 100 may include one or more HPUs 110 having only pump 130A and / or one or more HPUs 110 having only pump 130B. The system 100 may also utilize one or more HPSs 114 including a combination of at least one HPU 110 having pump 130A and at least one HPU 110 having only pump 130B, as discussed below.

[0066] In some embodiments, HPU 110 includes a reservoir 136 of hydraulic fluid in which each pump 130 may be submerged, such as Figure 2 The low pressure hydraulic fluid 124 may be returned to the reservoir 136 through the return port 138. Alternatively, the pump 130 may be located external to the hydraulic fluid reservoir 136 and draw hydraulic fluid from the reservoir 136 using, for example, a pressure intensifier.

[0067] Housing 139 may enclose reservoir 136 and pump 130, such as Figure 2 As instructed.

[0068] In some embodiments, each HPU 110 includes a pressure sensor 140 ( Figure 2 ), the pressure sensor is configured to sense the pressure of the hydraulic fluid flow 106 at the main output 133 and generate a pressure signal 142 indicative of the sensed pressure. The pressure signal 142 can be used to control the pump 130 of the HPU 110.

[0069] In some embodiments, each HPU includes redundant pressure sensors 140, such as sensors 140A and 140B that generate pressure signals 142A and 142B, respectively, that indicate the pressure of primary flow 106. Redundant pressure signals 142A and 142B may be used to ensure continued operation of HPU 110 in the event of a failure of one of pressure sensors 140. Additionally, pressure signals 142 generated by redundant pressure sensors 140 may be used to detect anomalies, as discussed below.

[0070] Figure 3 1 is a simplified diagram of an example of an HPS 114 according to an embodiment of the present disclosure. As described above, each HPS 114 includes two or more HPUs in HPU 110 that are each formed according to the embodiments described herein. Thus, although Figure 3 The example HPS 114 of FIG. 1 illustrates a combination of two HPUs 110A and 110B, but it should be understood that the HPS 114 may include three or more HPUs 110 .

[0071] The HPU 110 may be controlled by at least one controller (e.g., the system controller 126, the HPU controller 128, and / or the HPS controller 146) to generate the primary flows 106 (e.g., flows 106A and 106B) that are combined by the flow concentrator 148 to generate a flow for satisfying the test station 102 ( Figure 1 )'s desired combined main flow 150 of at least a portion of the hydraulic fluid flow demand.

[0072] In some embodiments, the HPS 114 includes an HPU 110A having one or more pumps 130A of a first type, and an HPU 110B having only pumps 130B of a second type. This allows the HPS 114 to utilize the advantages of each type of pump when generating the combined primary flow 150 .

[0073] HPS 114 may utilize one or more pressure sensors 140 to measure the pressure of combined primary flow 150 exiting through flow concentrator 148, such as Figure 3 In one example, the pressure sensor 140 may take the form of one or more pressure sensors 140 for each HPU 110 that measure the pressure at the corresponding primary output 133. Alternatively, the HPS 114 may include, for example, one or more pressure sensors 140 downstream of the primary output (such as at the output of the concentrator 148), such as Figure 3 As instructed.

[0074] In some embodiments, each pump 130B is in the form of a passive valve variable displacement hydraulic pump (e.g., a variable displacement simulation pump) with adjustable working volume, such as a passive valve variable displacement hydraulic pump used in a conventional HPU of a dynamic test system. These may include a conventional variable displacement radial pump, a variable displacement vane pump, a variable displacement axial pump, or another suitable conventional variable displacement pump.

[0075] Figure 4 1 is a simplified diagram of an example of a pump 130B according to an embodiment of the present disclosure. The pump 130B may include a plurality of piston pumps 160, each piston including a piston 162 contained within a cylinder 164. Each piston 162 is driven in a cyclic or reciprocating manner within its cylinder 164 by a circulation drive 166 using a motor 134. As with a conventional variable displacement hydraulic pump, the motor 134 drives the relative movement between the circulation drive 166 and the piston pump 160.

[0076] A valve assembly 168 connects the working volume 170 of each piston pump 160 to a high pressure port 172, which is connected to the main output 133, and a low pressure port 174, which is connected to the reservoir 136. The working volume 170 of each piston pump 160 is the maximum volume of hydraulic fluid that can be introduced into or driven out of the cylinder 164 through its port 176 during a stroke cycle of the piston 162.

[0077] The pump 130B includes a conventional displacement regulator 178 that operates to adjust the displacement 170 of each piston pump 160 in a conventional manner. This allows the pump 130B to switch from a zero displacement or near zero displacement mode (e.g., an idle mode), in which the pump 130B drives little, if any, hydraulic fluid flow 132B through the high pressure port 172, to a maximum displacement mode, in which the pump 130B drives maximum hydraulic fluid flow 132B through the high pressure port 172 while the motor 134 drives relative movement between the piston pump 160 and the circulation drive 166.

[0078] The valve assembly 168 may be, for example, a conventional valve assembly including passive valves (such as poppet check valves) that allow hydraulic fluid to flow into and out of the working volume 170 of each piston pump 160 in accordance with the movement of the piston 162. For example, when the circulation drive 166 moves the piston 160 toward its port 176 as indicated by arrow 180, hydraulic fluid flow is driven through the port 176. The valve assembly 168 allows flow to be delivered to the high pressure port 172 while preventing flow from being delivered to the low pressure port 174, as shown in FIG. Figure 4When the cyclic drive 166 moves the piston 162 away from its port 176, such as indicated by arrow 182, hydraulic fluid flow is drawn from the reservoir 136 through the low pressure port 174 and the port 176 and into the cylinder 164. Thus, in this manner, the cyclic movement of the piston 162 can drive the hydraulic fluid flow 132B received from the reservoir 136 through the high pressure port 172 and to the main output 133 to form the main flow 106, as shown in FIG. Figure 2 shown.

[0079] The circulation drive 166 and the displacement adjuster 178 may take any suitable form. For example, when the pump 130B is in the form of a conventional variable displacement radial pump, the circulation drive 166 may take the form of a cam, and the displacement adjuster 178 may adjust the eccentricity of the rotational axis of the piston pump 160 relative to the cam or the eccentricity of the rotational axis of the cam relative to the piston pump 160 to adjust the displacement. When the pump 130B is in the form of a conventional variable displacement vane pump, the circulation drive 166 may take the form of a cam ring that engages the vanes of the piston 162 when the piston pump 160 rotates relative to the cam ring. Here, the displacement adjuster 178 may take the form of, for example, the eccentricity of the rotational axis of the piston pump 160 relative to the cam ring.

[0080] Pump 130B may also take the form of a conventional variable displacement axial pump. Figure 5 A simplified side cross-sectional view of an example of such a conventional variable displacement axial pump is provided in . Here, the motor 134 can rotate the shaft 184 to which the piston pump 160 is attached relative to the wave plate 186, which operates as a cyclic drive 166. The wave plate 186 drives the cyclic movement of the piston 162 to draw hydraulic fluid into or drive hydraulic fluid out of the working volume 170 of the piston pump 160 in response to the movement of the piston pump 160 relative to the wave plate 186. The angle 188 of the wave plate 186 relative to the axis 189 of the shaft 184 determines the working volume 170 of each piston pump 160. For example, the working volume adjuster 178 can adjust the angle 188 from 90 degrees where the pump 130B is in its no-load mode to an angle 188 that maximizes the working volume 170 of the piston pump.

[0081] Figure 61 is a simplified diagram of an active valve hydraulic pump 130A according to an embodiment of the present disclosure. In some embodiments, pump 130A is in the form of a conventional active valve variable displacement hydraulic pump, which is generally referred to as an integrated reversing hydraulic pump or a digital displacement hydraulic pump. Some aspects of pump 130A are similar to pump 130B and are similarly labeled. Therefore, the circulation drive 166 and piston pump 160 of pump 130A can be similar to the circulation drive and piston pump of pump 130B. Additionally, pump 130A can take the form of a variable displacement radial pump, a variable displacement vane pump, or a variable displacement axial pump (such as disclosed in U.S. Patent No. 5,190,446).

[0082] The pump 130A may have a fixed displacement 190. As a result, the pump 130A is not provided with the displacement adjuster 178 of the pump 130B. Instead, the variable displacement of the hydraulic fluid flow 132A produced by the pump 130A is controlled by control of the active valve assembly 192 by the pump controller 193.

[0083] 7A to 7C 1 is a simplified diagram illustrating different operating modes of one of the piston pumps 160 of the pump 130A, which operating modes are achieved by the active valve assembly 192. The active valve assembly 192 may include a solenoid-operated poppet valve 194 for each piston pump 160, the poppet valve having a first state in which the poppet valve 196 is aligned with the port 176 of the piston pump 160 and blocks the flow of hydraulic fluid from the working volume 190 to the low pressure port 174, as shown in FIG. Fig. 7A The valve 194 also includes a second state in which a flow path 198 is open between the port 176 of the piston pump 160 and the low pressure port 174, as shown. Figure 7C The second state of valve 194 is generally its default (unpowered) state. The active valve assembly 192 may also include a passive valve 199 (e.g., a poppet-type check valve) that allows hydraulic fluid to flow from port 176 of piston pump 160 to high pressure port 172 when a pressure threshold is reached, such as Figure 7B shown.

[0084] When valve 194 is in the first state and circulation drive 166 moves piston 162 away from port 176, hydraulic fluid is drawn from reservoir 136 through low pressure port 174 into working volume 190 of piston pump 160, as shown in FIG. Fig. 7A When valve 194 is in the first state and circulation driver 166 moves piston 162 toward port 176, hydraulic fluid is driven from working volume 190 through port 176. Since the position of poppet valve 196 is set to prevent fluid flow from traveling to low pressure port 174, the movement of piston 162 pressurizes the hydraulic fluid and opens passive valve 199 to allow hydraulic fluid to travel to high pressure port 172, as shown in FIG. Figure 7B As a result, when the active valve 194 is in the first state, the piston pump 160 of the pump 130A operates in a similar manner to the piston pump 160 of the pump 130B ( Figure 4 ).

[0085] When valve 194 is in the second state, fluid path 198 is open between low pressure port 174 and port 176 of piston pump 160, as shown in FIG. Figure 7C As shown. Movement of the piston 162 driven by the circulation drive 166 toward the port 176 causes hydraulic fluid to be discharged from the working volume 190. Because the discharged hydraulic fluid is not sufficiently pressurized to overcome the threshold pressure of the passive valve 199, the hydraulic fluid travels to the low-pressure port 174 through the fluid path 198. Similarly, when the piston 162 moves away from the port 176 by the circulation drive 166, the hydraulic fluid can be drawn from the low-pressure port 174 into the working volume 190 through the fluid path 198. Therefore, when the active valve 194 is in the second state, the pump 130A can be in an unloaded state, in which the pump 130A does not drive the hydraulic fluid flow 132A to the main output 133, while the motor 134 drives the relative movement between the piston pump 160 and the circulation drive 166.

[0086] Therefore, as will be appreciated by those skilled in the art, the flow of hydraulic fluid 132A exhausted by the pump 130A to the main port 133 may be controlled based on the number of piston pumps 160 that are “activated” by setting the active valve 194 to the first state and the timing of the activation of the piston pumps 160 .

[0087] The controllers of the system (such as the system controller 126, the HPU controller 128, the HPS controller 146, and the pump controller 193) may take any suitable form to control the various functions described herein, such as Figure 8 2. The functions of an example controller 200 are shown in a simplified diagram of FIG. 2. The controller 200 may include one or more processors 202 and a memory 204. The one or more processors 202 are configured to implement various functions described herein in response to executing instructions contained in the memory 204.

[0088] The one or more processors 202 may be components of one or more computer-based systems and may include one or more control circuits, a microprocessor-based engine control system, and / or one or more programmable hardware components, such as a field programmable gate array (FPGA). The memory 204 represents a local and / or remote memory or computer-readable medium. Such a memory 204 includes any suitable computer-readable medium that complies with the subject matter of the patent and does not include transient waves or signals. Examples of the memory 204 include conventional data storage devices, such as hard disks, CD-ROMs, optical storage devices, magnetic storage devices, and / or other suitable data storage devices. The controller 200 may include a circuit system 206, which is used by the one or more processors 202 to receive input signals 208 (e.g., sensor signals 100), send control signals 210 (e.g., signals for controlling pumps, signals for actuating active valve assemblies, etc.), and / or transmit data 212, such as in response to the execution of instructions stored in the memory 204 by the one or more processors 202.

[0089] Some embodiments of the present disclosure relate to the operation of an HPU 110 having a combination of pumps 130A and 130B, wherein each type of pump 130 can be utilized based on its specific attributes to provide better response to changes in demand for hydraulic fluid flow by the test station 102 while efficiently supplying the required hydraulic fluid flow. In general, the active valve hydraulic pump 130A has the ability to adjust its hydraulic fluid output flow 132A much faster than the passive valve hydraulic pump 130B. For example, the pump 130A can adjust the number of piston pumps 160 activated by the state of the active valve 194 and control of the timing of activation, thereby adjusting the hydraulic fluid output flow 132A. However, the pumps 130B must use the displacement regulator 178 to adjust their hydraulic fluid output flow 132B. This requires a considerable amount of time to make a given change to the output flow 132B relative to the time required to make a similar change to the output flow 132A by the pump 130A. For example, the response time of pump 130A (eg, 50 milliseconds) may be approximately 10 times faster than the response time of pump 130B (eg, 2 to 4 seconds).

[0090] The passive valve hydraulic pump 130B generally suffers from higher heat losses and has lower volumetric energy efficiency when operating unloaded to the pump 130A. However, when operating under pressure at approximately 70% or more of its outlet flow capacity, the pump 130B has high volumetric efficiency.

[0091] In some embodiments of the present disclosure, the passive valve hydraulic pump 130B is generally used to provide a flow 132B that satisfies most of the required (e.g., steady state) hydraulic flow 106 at the main output 133, while the active valve hydraulic pump 130A is used to quickly provide the required hydraulic fluid flow 132A to meet increases or decreases in the required flow 106. Thus, the combined use of pumps 130A and 130B allows the HPU 110 to efficiently meet most of the flow demands, such as during steady state conditions, using pump 130B, while providing a much faster response to changing flow demands than conventional HPUs by using pump 130A.

[0092] When a test performed by one or more test stations 102 requires an increase in hydraulic fluid flow 106, the pressure at the main output 133 decreases. Likewise, a decrease in flow 106 required by a test station 102 causes an increase in pressure at the main output 133. These pressure changes are detected by, for example, the HPU controller 128 using the pressure signal 142 from the sensor 140. Thus, the output flows 132A and 132B of the pumps 130A and 130B can be controlled based on the pressure sensed at the main output 133.

[0093] In some embodiments, when the pressure indicated by the pressure signal 142 drops below a first pressure set point, one or more active valve hydraulic pumps 130A are activated to produce a corresponding flow 132A, and when the pressure indicated by the pressure signal 142 drops below a second pressure set point, one or more passive valve hydraulic pumps 130B are activated to produce a corresponding flow 132B. Additionally, for example, when the pressure at the main output rises above the first pressure set point, the pump 130 is controlled to reduce the generated hydraulic fluid flow 132, such as by deactivating one or more piston pumps 160 of the active valve hydraulic pump 130A and adjusting the displacement 170 of the piston pump 160 of the passive valve hydraulic pump 130B using the displacement adjuster 178.

[0094] The HPU controller 128 or another controller may store the desired first pressure set point in its memory 204 and issue a control signal 210 to the pump controller 193 of the pump 130A so that they operate as described above. The second pressure set point may be manually controlled (e.g., a pressure control valve) or controlled by a signal issued by the HPU controller 128 or another controller of the system 100. In one example, each pump 130B may include one or more remote pressure control valves, each of which controls the second pressure set point in response to a control signal 210 issued by the HPU controller 128 or another controller of the system 100.

[0095] In one embodiment, the first pressure set point is less than the second pressure set point. In one example, the first pressure set point is about 1 to 5% less than the second pressure set point, such as 2 to 3% less. As a result, when the pressure at the main output 133 is less than the second pressure set point but greater than the first pressure set point, the one or more passive valve hydraulic pumps 130B attempt to substantially meet the required flow 212 by adjusting the working volume 170 of the piston pump 160 using the working volume regulator 178. In the event that the pump 130B slows down in response to the increased flow demand, or is already operating at its maximum capacity, the pressure at the main output 133 will drop below the first pressure set point, thereby triggering the activation of the one or more piston pumps 160 of the active valve hydraulic pump 130A and the generation of flow 132A. This results in a rapid increase (line 212) of the main flow 106 to meet the required flow 210. When the pressure at the main output 133 rises above the first pressure set point, the output flow 132A from the one or more pumps 130A decreases because the pump 130B can take over and generate the majority of the flow 106 through the main output 133 (line 212).

[0096] This process Fig. 9 Line 210 indicates a demand for hydraulic fluid flow 106 through main output 133, such as by test station 102, grey line 212 illustrates main flow 106 of hydraulic fluid discharged through main output 133 and produced by flows 132A and 132B of pumps 130A and 130B, line 214 indicates hydraulic fluid flow 132B produced by pump 130B, and dashed line 216 indicates hydraulic fluid flow 132A produced by pump 130A.

[0097] From time t0 to time t1, the demand indicated by line 212 is continuous and steady and is less than the maximum capacity of pump 130B of HPU 110. Therefore, HPU 110 provides the required hydraulic fluid flow 212 at main output 133 using flow 132B produced by pump 130B. Here, the pressure at main output 133 is stabilized at or near the second pressure set point. Since the pressure is above the first pressure set point, pump 130A is substantially or completely deactivated and, therefore, does not produce significant hydraulic fluid flow 132A.

[0098] At time t1, as indicated by line 210, a sharp increase in hydraulic fluid flow is required. Initially, the pressure at the main output 133 drops below the second pressure set point, thereby triggering the pumps 130B to increase their hydraulic fluid output flows 132B, such as by changing the displacement 170 of the piston pump 160 using the displacement adjuster 178. However, because the pumps 130B cannot quickly meet the required flow, the pressure at the main output 133 continues to drop and drops below the first pressure set point. This triggers the activation of one or more pumps 130A to quickly produce hydraulic fluid output flows 132A, which when combined with the output flow 132B from the pumps 130B produce a combined output flow (line 212) at the main output 133 that matches the required flow 210.

[0099] From time t2 to time t3, increasing hydraulic fluid flow 132B output from pump 130B provides a more significant contribution to combined flow 106 (line 212), and output flow 132A of pump 130A decreases accordingly. During this period, the pressure at the main output 133 fluctuates around the first pressure set point.

[0100] After time t3, the output flow 132B of the pump 130B stabilizes to produce a majority of the desired flow 106. In the illustrated example, the desired flow is greater than the combined flow of the maximum output flows 132B of the pump 130B. Thus, unlike the period from time t0 to time t1 during which the pump 130B was able to produce the desired flow 210, thereby allowing the pump 130A to be deactivated, the pump 130A is used after time t3 to produce a portion of the desired flow 210 in response to the pressure at the main output 133 fluctuating about the first pressure set point.

[0101] In one embodiment, the first pressure set point is greater than the second pressure set point. In one example, the first pressure set point is approximately 1 to 5%, such as 2 to 3%, greater than the second pressure set point. When the pressure at the main output 133 is less than the first pressure set point but greater than the second pressure set point, one or more active valve hydraulic pumps 130A attempt to substantially meet the required flow 106 by activating one or more piston pumps 160. In the event that pump 130A cannot meet the demand for increased flow, or is already operating at its maximum capacity, the pressure at the main output 133 will drop below the second pressure set point, thereby triggering the activation of one or more passive valve hydraulic pumps 130B and the generation of flow 132B. This causes an increase in the main flow 106. When the pressure at the main output 133 rises above the second pressure set point, the output flow 132B from the one or more pumps 130B decreases because pump 130A takes over and generates most of the flow 106 through the main output 133.

[0102] This process Fig.10 Line 210 indicates a demand for hydraulic fluid flow 106 through main output 133, for example, by test station 102, grey line 212 represents main flow 106 of hydraulic fluid discharged through main output 133 and produced by flows 132A and 132B of pumps 130A and 130B, line 214 indicates hydraulic fluid flow 132B produced by pump 130B, and dashed line 216 indicates hydraulic fluid flow 132A produced by pump 130A.

[0103] From time t0 to time t1, the demand indicated by line 212 is continuous and steady, and is less than the maximum capacity of pump 130A of HPU 110. Therefore, HPU 110 provides the required hydraulic fluid flow 106 at main output 133 using flow 132A produced by pump 130A. Here, the pressure at main output 133 is stabilized at or near the first pressure set point. Since the pressure is above the second pressure set point, pump 130B is substantially or completely deactivated, and therefore does not produce significant hydraulic fluid flow 132B.

[0104] At time t1, as indicated by line 210, a dramatic increase in hydraulic fluid flow is required. Initially, the pressure at the main output 133 drops below a first pressure set point, thereby triggering the pumps 130A to increase their hydraulic fluid output flow 132A, such as by activating one or more piston pumps 160. However, in the event that the pumps 130A are unable to quickly meet the required flow, the pressure at the main output 133 continues to drop and drops below a second pressure set point. This triggers the activation of one or more pumps 130B to produce an increased hydraulic fluid output flow 132B, such as by changing the displacement 170 of the piston pumps 160 using the displacement adjuster 178. When the output flow 132B merges with the output flow 132A from the pumps 130A, a combined output flow 106 (line 212) is produced at the main output 133 that matches the required flow 210.

[0105] From time t2 to time t3, increasing hydraulic fluid flow 132A output from pump 130A provides a more significant contribution to combined flow 106 (line 212), and output flow 132B from pump 130B decreases accordingly. During this period, the pressure at the main output 133 fluctuates around the second pressure set point.

[0106] After time t3, the output flow 132A of the pump 130A stabilizes to produce most of the required flow 106 (line 210). In the illustrated example, the required flow is less than the combined flow of the maximum output flows 132A of the pump 130A. Therefore, the pump 130A is primarily used after time t3 to produce the required flow 106 (line 210) in response to the pressure at the main output 133 fluctuating around the second pressure set point.

[0107] In yet another embodiment, the first pressure set point and the second pressure set point are set to substantially the same pressure (e.g., + / - 0.8%). Thus, as the pressure at the main output 133 fluctuates about the first pressure set point and the second pressure set point, flows 132A and 132B from the active valve hydraulic pump 130A and the passive valve hydraulic pump 130B are generated. When the required flow increases dramatically, causing the pressure at the main output 133 to drop, the flows 132A and 132B are increased to meet the demand, wherein the flow 132A generally increases faster than the flow 132B. Likewise, as the required flow decreases, the pressure at the main output 133 increases, causing the pumps 130A and 132B to reduce their flows 132A and 132B until the pressure stabilizes about the first pressure set point and the second pressure set point.

[0108] Additional embodiments relate to methods of operating the HPU 110, such as using the HPU controller 128. The HPU 110 can be formed according to the embodiments described herein. Thus, the HPU 110 can, for example, include: a reservoir 136; a main output 133; a pressure sensor 140; at least one active valve hydraulic pump 130A, the at least one active valve hydraulic pump configured to drive a first flow portion 132A of the main flow 106 through the main output 133 when the pressure of the main flow 106 indicated by the pressure signal 142 is below a first pressure set point; and at least one passive valve hydraulic pump 130B, the at least one passive valve hydraulic pump configured to drive a second flow portion 132B of the main flow 106 through the main output 133 when the pressure signal 142 indicates that the pressure is below a second pressure set point, such as Figure 2 shown.

[0109] Fig.11 is a flow chart illustrating an example of a method of operating an HPU according to an embodiment of the present disclosure. At 220 of the method, when the pressure signal 142 indicates that the pressure at the main output 133 is below the first pressure set point, one or more active valve hydraulic pumps in the at least one active valve hydraulic pump 130A are used to drive a portion of the main flow 106. At 222, when the pressure signal 142 indicates that the pressure at the main output 133 is above the first pressure set point, the at least one active valve hydraulic pump 130A is deactivated.

[0110] Similarly, at 224 of the method, when the pressure signal 142 indicates that the pressure at the main output 133 is below the second pressure set point, one or more of the at least one passive valve hydraulic pump 130B is used to drive a portion of the main flow 106. At 226, when the pressure signal 142 indicates that the pressure at the main output 133 is above the second pressure set point, the at least one passive valve hydraulic pump 130B is deactivated.

[0111] When the second pressure set point is higher than the first pressure set point (e.g., 1-5%), the HPU 110 refers to Fig. 9 For example, during step 220, one or more passive valve hydraulic pumps 130B are used in conjunction with pump 130A to drive the main flow 106, and in step 224, when the pressure at the main output 133 is above the first pressure set point, only one or more passive valve hydraulic pumps 130B are used to drive the main flow 106.

[0112] When the first pressure set point is higher than the second pressure set point (e.g., 1-5%), the HPU 110 refers to Fig.10 The diagram operates as described above. For example, during step 224, one or more active valve hydraulic pumps 130A are used in combination with the passive valve hydraulic pump 130B to drive the main flow 106, and in step 224, when the pressure at the main output 133 is above the second pressure set point, only the one or more active valve hydraulic pumps 130A are used to drive the main flow 106.

[0113] Embodiments of the present disclosure also relate to operating HPS 114 ( Figure 3 ) methods, which are similar to the methods of operating HPU 110. Fig.12 1 is a flow chart illustrating one example of a method of operating an HPS 114 according to an embodiment of the present disclosure, which method may be implemented using, for example, an HPS controller 146. The HPS 114 may be formed according to embodiments described herein. Thus, the HPS 114 may, for example, include: a first HPU 110A including a reservoir 136, a main output 133, and at least one active valve hydraulic pump 130A, the at least one active valve hydraulic pump being configured to drive a flow portion 132A of a first main flow 106A through the main output 133 when a pressure indicated by a pressure signal 142 from a pressure sensor 140 is below a first pressure set point; and a second HPU 110B including a main output 133, and at least one passive valve hydraulic pump 130B, the at least one passive valve hydraulic pump being configured to drive a flow portion 132B of a second main flow 106B through the main output 133 when a pressure indicated by a pressure signal 142 from a pressure sensor 140 is below a second pressure set point. Additionally, the HPS 114 may include a flow combiner 148 configured to combine the first main flow 106A and the second main flow 106B into a combined flow 150 .

[0114] At 230 of the method, when the pressure at the main output 133 is below the first pressure set point, one or more of the at least one active valve hydraulic pump 130A of the first HPU 110A is used to drive the first main flow 106A. At 232, when the pressure at the main output 133 is above the first pressure set point, the at least one active valve hydraulic pump 130A of the HPU 110A is deactivated. Similarly, at 234 of the method, when the pressure at the main output 133 is below the second pressure set point, one or more of the at least one passive valve hydraulic pump 130B of the second HPU 110B is used to drive the second main flow 106B. At 236, when the pressure at the main output 133 is above the second pressure set point, the at least one passive valve hydraulic pump 130B of the HPU 110B is deactivated. In this manner, the HPUs 110A and 110B may be used to provide the desired combined flow 150.

[0115] During step 230, when the second pressure set point is higher (e.g., 1-5%) than the first pressure set point, one or more passive valve hydraulic pumps 130B of HPU 110B are used in conjunction with pump 130A of HPU 110A to produce the combined flow 150, and in step 236, when the pressure at the main output 133 is higher than the first pressure set point, only one or more passive valve hydraulic pumps 130B of HPU 110B are used to produce the combined flow 150.

[0116] During step 234, when the first pressure set point is higher (e.g., 1-5%) than the second pressure set point, one or more active valve hydraulic pumps 130A of HPU 110A are used in conjunction with the passive valve hydraulic pump 130B of HPU 110B to produce the combined flow 150, and in step 230, when the pressure at the main output 133 is higher than the second pressure set point, only one or more active valve hydraulic pumps 130A of HPU 110A are used to produce the combined flow 150.

[0117] Additional embodiments of the present disclosure involve using two or more pressure sensors 140 by the HPU 110 to measure the pressure of the primary flow 106 at the primary output 133, such as Figure 2 and / or by the HPS using two or more pressure sensors 140 to measure the pressure of the combined main flow 150 (such as the concentrator 148 or the main output 133 of one or both of the HPUs 110A and 110B), such as Figure 3In one embodiment, a controller (such as HPU controller 128 or HPS controller 146) monitoring pressure signal 142 from pressure sensor 140 compares the value associated with signal 142 to a reference value range corresponding to expected valid values, which reference value range may be stored in the controller's memory 204. If one of the signal values ​​is outside the reference range, it may be discarded and another signal value within the reference range may be used to facilitate the pump control functions described above. The controller may use circuitry 206 to issue a notification to an operator or administrator of the system regarding an abnormal condition of one of the pressure sensors.

[0118] If both signal values ​​are outside the reference range, this may indicate a serious abnormal condition (eg, power loss, fluid leakage, etc.) and the controller may issue a notification indicating the abnormal condition to an operator or administrator of the system.

[0119] In one embodiment, the controller compares the signal values ​​to each other. When the signal values ​​substantially match (e.g., + / - 10%), it is assumed that the sensor 140 of the HPU 110 or HPS 114 is operating normally. If the signal values ​​substantially do not match, the controller may issue a notification to an operator or administrator of the system indicating an abnormal condition in the form of a problem with one of the pressure sensors 140, a loss of a sensor signal, or another abnormal condition indicated by the mismatched pressure signals 142.

[0120] Notifications sent by the controller may take any suitable form and may be sent by Figure 8 The data in 212 is represented. Examples of notifications include audible and / or visual alarms, and / or electronic messages (control panel messages, emails, text messages, etc.) to an operator or administrator of the system.

[0121] Alternatively, the previously described embodiments may be modified by using one or more flow sensors in place of each of the one or more pressure sensors 140. Each flow sensor generates a flow signal indicative of the flow of the sensed fluid flow and may be used to control the pump 130 in a manner similar to the pressure indicated by the pressure signal 142 from one of the pressure sensors 140. Thus, each of the one or more pressure sensors 140 illustrated in the figures may represent a corresponding flow sensor, and each of the illustrated pressure signals 142 may represent a flow signal.

[0122] therefore, Fig.11 The method can be modified to control the pump using the sensed flow rate instead of the sensed pressure. Fig.11At step 220 of the method, when the flow indicated by the corresponding flow sensor is below a first flow set point, one or more of the at least one active valve hydraulic pumps are used to drive a portion of the main flow. At 222, when the flow is above the first flow set point, the at least one active valve hydraulic pump is deactivated. At 224, when the flow is below a second flow set point, one or more of the at least one passive hydraulic pumps are used to drive a portion of the main flow. At 226, when the flow is above the second flow set point, the at least one passive hydraulic pump is deactivated.

[0123] Although embodiments of the present disclosure have been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the present disclosure.

Claims

1. A hydraulic power unit, comprising: a reservoir containing a hydraulic fluid; a main output through which a main flow of the hydraulic fluid is discharged; a pressure sensor having a pressure signal indicative of a pressure of the primary flow; at least one active valve hydraulic pump having a variable displacement, each active valve hydraulic pump configured to drive a first flow portion of the main flow from the reservoir to the main output when the pressure signal is below a first pressure set point; at least one passive valve hydraulic pump having a variable displacement, each passive valve hydraulic pump configured to drive a second flow portion of the main flow from the reservoir to the main output when the pressure signal is below a second pressure set point; as well as A housing houses a reservoir, the at least one active valve hydraulic pump, and the at least one passive valve hydraulic pump.

2. The hydraulic power unit according to claim 1, wherein: The first pressure set point is less than the second pressure set point; or The first pressure set point is greater than the second pressure set point.

3. The hydraulic power unit according to claim 2, wherein: The first pressure set point is approximately 1-5% less than the second pressure set point.

4. The hydraulic power unit according to claim 2, wherein: The first pressure set point is approximately 1-5% greater than the second pressure set point.

5. The hydraulic power unit according to claim 1, wherein: The first pressure set point is equal to the second pressure set point.

6. The hydraulic power unit of claim 1, further comprising at least one controller configured to set the first pressure set point and the second pressure set point.

7. The hydraulic power unit of claim 1, wherein: The at least one passive valve hydraulic pump includes a plurality of the passive valve hydraulic pumps.

8. The hydraulic power unit of claim 7, wherein: The at least one active valve hydraulic pump includes a plurality of the active valve hydraulic pumps.

9. The hydraulic power unit of claim 1, wherein: The at least one active valve hydraulic pump includes a plurality of the active valve hydraulic pumps.

10. The hydraulic power unit of claim 1, wherein: Each active valve hydraulic pump includes: a low pressure port connected to the fluid reservoir; a high voltage port connected to the main output; Multiple piston pumps; a motor configured to drive a cyclic variation in the working volume of each piston pump; a plurality of active valves, each active valve corresponding to one of the plurality of piston pumps and configured to place the piston pump in an activated state in which the cyclic variation of the working volume drives the first flow portion of hydraulic fluid from the working volume through the high pressure port, and a deactivated state in which a fluid path is formed between the working volume and the reservoir or the low pressure port; and A pump controller is configured to control each of the active valves to individually set the piston pump to be in the activated state or the deactivated state.

11. The hydraulic power unit of claim 10, wherein: Each passive valve hydraulic pump includes: a low pressure port connected to the fluid reservoir; a high voltage port connected to the main output; a plurality of piston pumps, each piston pump configured to draw hydraulic fluid into an adjustable working volume through the low pressure port and drive a second flow portion of the hydraulic fluid from the adjustable working volume through the high pressure port; and A motor is configured to drive cyclic variation of the adjustable displacement of each piston pump.

12. A method of operating a hydraulic power unit, the hydraulic power unit comprising: a reservoir containing a hydraulic fluid; a main output through which a main flow of said hydraulic fluid from said reservoir is discharged; a pressure sensor having a pressure signal indicative of a pressure of the primary flow; at least one active valve hydraulic pump having variable displacement; at least one passive valve hydraulic pump having variable displacement; as well as a housing accommodating the reservoir, the at least one active valve hydraulic pump and the at least one passive valve hydraulic pump, The method comprises: driving a first flow portion of the main flow using one or more of the at least one active valve hydraulic pump when the pressure signal indicates that the pressure of the main flow is below a first pressure set point; deactivating the at least one active valve hydraulic pump when the pressure signal indicates that the pressure of the primary flow is above the first pressure set point; driving a second flow portion of the main flow using one or more of the at least one passive hydraulic pumps when the pressure signal indicates that the pressure of the main flow is below the second pressure set point; and The at least one passive valve hydraulic pump is deactivated when the pressure signal indicates that the pressure of the main flow is above the second pressure set point.

13. The method of claim 12, wherein: The first pressure set point is less than the second pressure set point; or The first pressure set point is greater than the second pressure set point.

14. The method of claim 13, wherein: The first pressure set point is approximately 1-5% less than the second pressure set point.

15. The method of claim 13, wherein: The first pressure set point is approximately 1-5% greater than the second pressure set point.

16. The method of claim 12, wherein: The first pressure set point is equal to the second pressure set point.

17. The method of claim 12, wherein: The at least one passive valve hydraulic pump includes a plurality of the passive valve hydraulic pumps.

18. The method of claim 12, wherein: The at least one active valve hydraulic pump includes a plurality of the active valve hydraulic pumps.

19. The method of claim 12, wherein: Each active valve hydraulic pump includes: a low pressure port connected to the fluid reservoir; a high voltage port connected to the main output; a plurality of first piston pumps; a motor configured to drive a cyclic variation in the displacement of each first piston pump; a plurality of active valves, each active valve being configured to place one of the plurality of first piston pumps in an activated state in which the cyclic variation of the working volume drives a portion of the first flow portion through the high pressure port, and a deactivated state in which a fluid path is formed between the working volume and the reservoir or the low pressure port; and a pump controller configured to control each of the active valves to individually set the first piston pump to be in the activated state or the deactivated state; and Each passive valve hydraulic pump includes: a low pressure port connected to the fluid reservoir; a high voltage port connected to the main output; a plurality of second piston pumps, each second piston pump configured to draw hydraulic fluid into an adjustable working volume through the low pressure port and to drive a portion of the second flow portion of hydraulic fluid from the adjustable working volume through the high pressure port; and A motor is configured to drive cyclic variation of the adjustable displacement of each of the plurality of second piston pumps.

20. A hydraulic power system comprising: At least one first hydraulic power unit, each first hydraulic power unit comprising: a first reservoir containing a hydraulic fluid; a first main output through which the first main flow of hydraulic fluid is discharged; a first pressure sensor having a first pressure signal indicative of a first pressure of the first primary flow; at least one active valve hydraulic pump, each active valve hydraulic pump configured to drive a flow portion of the first main flow from the first reservoir to the first main output when the first pressure signal indicates that the first pressure is below a first pressure set point; and a first housing accommodating the first reservoir and the at least one active valve hydraulic pump; at least one second hydraulic power unit, each second hydraulic power unit comprising: a second reservoir containing a hydraulic fluid; a second primary output through which the second primary flow of hydraulic fluid is discharged; a second pressure sensor having a second pressure signal indicative of a second pressure of the second primary flow; at least one passive valve hydraulic pump, each passive valve hydraulic pump configured to drive a flow portion of the second main flow from the second reservoir to the second main output when the second pressure signal indicates that the second pressure is below a second pressure set point; and a second housing accommodating the second reservoir and the at least one passive valve hydraulic pump; and A flow concentrator is configured to combine the first main flow and the second main flow into a combined main flow.

Images