Hydraulic power generation 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

Technical Field

[0001] 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

[0002] 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. The 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.

[0003] 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 rotating swash plate to vary the working volume of the piston pump.

[0004] There is a continuing need for improvements in dynamic testing systems including, for example, improved hydraulic fluid flow generation to meet rapidly changing flow demands, and improved control of hydraulic pumps to increase energy efficiency, reduce energy spikes, and reduce wear and tear on pump components, among other things. Summary of the invention

[0005] Embodiments of the present disclosure relate to methods of controlling a hydraulic power unit of a dynamic test system and a dynamic test system configured to perform these methods.

[0006] In some embodiments, a hydraulic power unit of a dynamic test system includes: at least one controller; a plurality of hydraulic pumps configured to generate a variable primary flow of hydraulic fluid for driving a hydraulic actuator of at least one test station during execution of at least one test. In one embodiment of the method, at least one test flow profile is obtained, each test flow profile identifying an estimate of a hydraulic fluid flow demand over time corresponding to execution of one of the at least one test. During execution of the at least one test, the variable primary flow of hydraulic fluid is generated using a plurality of unique subsets of the hydraulic pumps. Each unique subset is selected based on the at least one test flow profile.

[0007] In some embodiments, the method includes identifying, for each of a plurality of time periods, a corresponding unique subset of the unique subset of hydraulic pumps required to produce a main flow that exceeds the sum of the estimated hydraulic fluid flow demand values ​​corresponding to the time period based on the at least one test flow pattern; and generating the variable main flow includes using the identified corresponding unique subset of the hydraulic pumps to generate the variable main flow during each of the plurality of time periods.

[0008] In some embodiments, each of the hydraulic pumps is configured to produce up to a maximum hydraulic fluid flow; and a sum of the maximum flows of the determined subset of the hydraulic pumps exceeds a sum of hydraulic fluid flow demand estimates over a corresponding time period.

[0009] In some embodiments, during each of the multiple time periods, a corresponding sum of the hydraulic fluid flow demand estimates is between a lower boundary flow threshold and an upper boundary flow threshold among a plurality of flow thresholds; each flow threshold corresponds to one of the unique subsets of the hydraulic pumps; and for each time period, identifying the corresponding one of the unique subsets of the hydraulic pumps includes identifying the corresponding one of the unique subsets based on the upper flow threshold.

[0010] In some embodiments, each of the hydraulic pumps includes a start state and a stop state, in which the hydraulic pump contributes significantly to the variable main flow, and in the stop state, the hydraulic pump does not contribute significantly to the variable main flow; and for at least one of the time periods, generating the variable main flow includes transitioning one or more of the hydraulic pumps in the corresponding unique subset from the stop state to the start state.

[0011] In some embodiments, transitioning one or more of the hydraulic pumps in the corresponding unique subset from the deactivated state to the activated state occurs a predetermined time period before the start of the at least one of the time periods.

[0012] In some embodiments, the predetermined period of time is greater than about 3 seconds.

[0013] In some embodiments, each hydraulic pump includes a motor having a start state and a stop state, in which the motor is powered and drives the hydraulic pump, and in which the motor is not powered; and transitioning one or more of the hydraulic pumps in the determined subset from the stop state to the start state includes transitioning the motor of the one or more hydraulic pumps from the stop state to the start state.

[0014] In some embodiments, the deactivated state of each hydraulic pump includes an idle state of the hydraulic pump, in which the motor is in an activated state.

[0015] In some embodiments, for one or more of said time periods, motors of hydraulic pumps that are not in said determined subset during said time period are set to said deactivated state.

[0016] In some embodiments, the hydraulic power unit includes: a reservoir containing a hydraulic fluid;

[0017] a main output through which the variable main flow of hydraulic fluid is discharged; and the plurality of hydraulic pumps including at least one active valve hydraulic pump having a variable displacement and at least one passive valve hydraulic pump having a variable displacement.

[0018] In some embodiments, each subset includes one of the at least one active valve hydraulic pump.

[0019] In some embodiments, each active valve hydraulic pump includes: a low-pressure port connected to the fluid reservoir; a high-pressure port connected to the main output; a plurality of piston pumps; a motor configured to drive cyclic changes 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 an inactivated state, in which the cyclic changes in the working volume drive at least a portion of the variable main flow from the working volume through the high-pressure port, and 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 piston pump to the activated state or the inactivated state.

[0020] In some embodiments, each passive valve hydraulic pump includes: a low pressure port connected to the fluid reservoir; a high pressure port connected to the main output; a plurality of piston pumps, each piston pump being configured to draw hydraulic fluid through the low pressure port and into an adjustable working volume, and to drive at least a portion of the second flow portion of the hydraulic fluid from the adjustable working volume through the high pressure port; and a motor configured to drive cyclic changes in the adjustable working volume of each piston pump.

[0021] In some embodiments, obtaining at least one test flow pattern includes measuring at least one hydraulic fluid flow during a previous execution of the at least one test.

[0022] In some embodiments, measuring at least one flow includes measuring at least one hydraulic fluid flow over time using one or more flow meters, the flow meters including one or more flow meters respectively located at a flow input to one of the at least one test stations, and one or more flow meters respectively located at a flow output of one of the at least one test stations, and / or a flow meter located at a main output of the hydraulic power unit.

[0023] An example of a dynamic test system includes at least one test station, a hydraulic power unit, and at least one controller. Each test station is configured to apply force and / or displacement to a test object using a hydraulic actuator during execution of a test. The hydraulic power unit includes a plurality of hydraulic pumps configured to generate a variable primary flow of hydraulic fluid that drives the hydraulic actuator of the at least one test station during execution of at least one test. The at least one controller is configured to obtain at least one test flow pattern, each test flow pattern identifying an estimate of hydraulic fluid flow demand over time corresponding to execution of one of the at least one test, and to generate the variable primary flow of hydraulic fluid using a plurality of unique subsets of the plurality of hydraulic pumps during execution of the at least one test. Each unique subset is selected based on the at least one test flow pattern.

[0024] In some embodiments, the at least one controller is configured to: for each of a plurality of time periods, identify, based on the at least one test flow pattern, a corresponding unique subset of the unique subset of hydraulic pumps required to produce a main flow that exceeds the sum of the estimated hydraulic fluid flow demand values ​​corresponding to the time period; and use the identified corresponding unique subset of the hydraulic pumps to produce the variable main flow during each of the plurality of time periods.

[0025] In some embodiments, each of the hydraulic pumps is configured to produce up to a maximum hydraulic fluid flow; and a sum of the maximum flows of the determined subset of the hydraulic pumps exceeds a sum of the hydraulic fluid flow demand estimates over the time period.

[0026] In some embodiments, during each of the plurality of time periods, a corresponding sum of the hydraulic fluid flow demand estimates is between a lower boundary flow threshold and an upper boundary flow threshold among a plurality of flow thresholds; each flow threshold corresponds to one of the unique subsets of the hydraulic pumps; and for each time period, the corresponding one of the unique subsets of the hydraulic pumps is identified based on the upper flow threshold.

[0027] In some embodiments, each of the hydraulic pumps includes a start state and a stop state, in which the hydraulic pump contributes significantly to the variable main flow, and in the stop state, the hydraulic pump does not contribute significantly to the variable main flow; and for at least one of the time periods, one or more of the hydraulic pumps in the corresponding unique subset are transitioned from the stop state to the start state to generate the variable main flow.

[0028] In some embodiments, for at least one of the time periods, before the start of at least one of the time periods, one or more of the hydraulic pumps in the corresponding unique subset are transitioned from the deactivated state to the activated state to generate the variable main flow.

[0029] In some embodiments, the predetermined period of time is greater than about 3 seconds.

[0030] In some embodiments, each hydraulic pump includes a motor having a start state and a stop state, in which the motor is powered and drives the hydraulic pump, and in the stop state, the motor is not powered; and the one or more hydraulic pumps in the determined subset are transitioned from the stop state to the start state by transitioning the motor of one or more hydraulic pumps in the determined subset from the stop state to the start state.

[0031] In some embodiments, the deactivated state of each hydraulic pump includes an idle state of the hydraulic pump, in which the motor is in an activated state.

[0032] In some embodiments, for one or more of said time periods, motors of hydraulic pumps that are not in said determined subset during said time period are set to said deactivated state.

[0033] In some embodiments, the hydraulic power unit includes: a reservoir, which contains hydraulic fluid; a main output, through which a variable main flow of the hydraulic fluid is discharged; and the plurality of hydraulic pumps, including at least one active valve hydraulic pump with variable displacement and at least one passive valve hydraulic pump with variable displacement.

[0034] In some embodiments, each subset includes one of the at least one active valve hydraulic pump.

[0035] In some embodiments, each active valve hydraulic pump includes: a low-pressure port connected to the fluid reservoir; a high-pressure port connected to the main output; a plurality of piston pumps; a motor configured to drive cyclic changes 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 an inactivated state, in which the cyclic changes in the working volume drive at least a portion of the variable main flow from the working volume through the high-pressure port, and 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 piston pump to the activated state or the inactivated state.

[0036] In some embodiments, each passive valve hydraulic pump includes: a low pressure port connected to the fluid reservoir; a high pressure port connected to the main output; a plurality of piston pumps, each piston pump being configured to draw hydraulic fluid through the low pressure port and into an adjustable working volume, and to drive at least a portion of the second flow portion of the hydraulic fluid from the adjustable working volume through the high pressure port; and a motor configured to drive cyclic changes in the adjustable working volume of each piston pump.

[0037] In some embodiments, the system includes: one or more flow meters respectively located at the flow input of one of the at least one test stations; one or more flow meters respectively located at the flow output of one of the at least one test stations; and / or a flow meter located at the main output of the hydraulic power unit, wherein each flow meter is configured to measure the flow of hydraulic fluid.

[0038] In another method of controlling a hydraulic power unit of a dynamic test system using at least one controller, the hydraulic power unit includes: 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 main pressure of the main flow; and a plurality of variable displacement hydraulic pumps, each of which is configured to drive a portion of the main flow. Each variable displacement hydraulic pump includes a plurality of piston pumps, a motor having an activated state and a deactivated state, and a pressure set point, wherein the motor drives a cyclic change in the working volume of each piston pump in the activated state. The pressure set point is selectable between an inoperable pressure set point range below an expected operating range of the main pressure, wherein the variable displacement hydraulic pump does not contribute to the main flow, and an operable pressure set point within the expected operating range of the main pressure, wherein the variable displacement hydraulic pump is driven to contribute to the main flow. In one embodiment of the method, one of the variable displacement hydraulic pumps is controlled by operating the variable displacement hydraulic pump for a first predetermined period of time when the pressure set point is set to a first inoperable pressure set point within the inoperable pressure setting range, and operating the variable displacement hydraulic pump when the pressure set point is set to the operable pressure set point.

[0039] In some embodiments, operating the variable displacement hydraulic pump for the first predetermined period of time occurs before operating the variable displacement hydraulic pump when the pressure set point is set to the operable pressure set point.

[0040] In some embodiments, operating the variable displacement hydraulic pump for the first predetermined period of time includes transitioning the motor from the deactivated state to the activated state.

[0041] In some embodiments, after operating the variable displacement hydraulic pump for a first predetermined period of time and before operating the variable displacement hydraulic pump when the pressure set point is set to the operable pressure set point, the variable displacement hydraulic pump is operated for a second predetermined period of time when the pressure set point is set to a second inoperable pressure set point within the inoperable pressure set point range, wherein the second pressure set point is higher than the first pressure set point.

[0042] In some embodiments, the first time period and the second time period are substantially equal; the first time period is greater than the second time period; or the first time period is less than the second time period.

[0043] In some embodiments, operating the variable displacement hydraulic pump for the first predetermined period of time occurs after operating the variable displacement hydraulic pump when the pressure set point is set to the operable pressure set point.

[0044] In some embodiments, operating the variable displacement hydraulic pump for the first predetermined period of time includes transitioning the motor from the activated state to the deactivated state.

[0045] In some embodiments, after operating the variable displacement hydraulic pump when the pressure set point is set to the operable pressure set point and before operating the variable displacement hydraulic pump for a first predetermined period of time, the variable displacement hydraulic pump is operated for a second predetermined period of time when the pressure set point is set to a second inoperable pressure set point within the inoperable pressure set point range, wherein the second pressure set point is higher than the first pressure set point.

[0046] In some embodiments, the first time period and the second time period are substantially equal; the first time period is greater than the second time period; or the first time period is less than the second time period.

[0047] In some embodiments, operating the variable displacement hydraulic pump for the first predetermined time period includes using a controller to set the pressure set point to the first non-operable pressure set point; and operating the variable displacement hydraulic pump when the pressure set point is set to one of the operable pressure set points includes using the controller to set the pressure set point to the operable pressure set point.

[0048] 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

[0049] Figure 1 is a simplified diagram of an example of a dynamic testing system according to an embodiment of the present disclosure.

[0050] Figure 2 is a simplified diagram of an example of a hydraulic power unit according to an embodiment of the present disclosure.

[0051] Figure 3 is a simplified diagram of an example of a hydraulic power system according to an embodiment of the present disclosure.

[0052] Figure 4is a simplified diagram of an example of a passive valve hydraulic pump according to an embodiment of the present disclosure.

[0053] Figure 5 is a simplified side cross-sectional view of an example of a variable displacement axial pump according to an embodiment of the present disclosure.

[0054] Figure 6 is a simplified diagram of an example of an active valve hydraulic pump according to an embodiment of the present disclosure.

[0055] 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.

[0056] Figure 8 is a simplified diagram of a controller according to an embodiment of the present disclosure.

[0057] Fig. 9 is a schematic diagram of an example of a test station according to an embodiment of the present disclosure.

[0058] Fig.10 is a chart illustrating a test flow pattern according to an embodiment of the present disclosure.

[0059] Fig.11 is a flow chart illustrating a method of controlling a hydraulic power unit to generate a variable primary flow for driving a hydraulic actuator of at least one test station during execution of at least one test according to an embodiment of the present disclosure.

[0060] Fig.12 Included are graphs illustrating an example pair of overlapping test flow patterns and the operation of a hydraulic power unit according to an embodiment of the present disclosure.

[0061] Fig.13 is a flow chart illustrating a method of controlling a hydraulic pump of a hydraulic power unit according to an embodiment of the present disclosure.

[0062] Fig.14 and Fig.15 is a graph illustrating an example of adjusting a pressure set point of a hydraulic pump over time to transition the pump between a deactivated state and an activated state according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0063] 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 characters 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.

[0064] 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.

[0065] The 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 the test station 102.

[0066] 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 of the HPUs 110 is controlled to produce a desired combined hydraulic fluid flow, as discussed below.

[0067] The system 100 may include a reservoir 116 that stores pressurized hydraulic fluid received from the HPU 110 and / or the HPS 114. The reservoir 116 may discharge a flow 118 of hydraulic fluid that may be supplied to the test station 102.

[0068] In some embodiments, system 100 may include a distributor 120 that receives a flow of hydraulic fluid from HPU 110, HPS 114, and / or reservoir 116 and distributes the flow of hydraulic fluid to test stations 102 as indicated by arrows 122. Other arrangements may also be used to form system 100.

[0069] The system 100 may be a closed system in which a flow of low-pressure hydraulic fluid 124 used by the test station 102 is returned back to the HPU 110 , such as through the hydraulic distribution system 120 , for example.

[0070] System controller 126 may be operable to control various aspects of system 100 , including the functioning of HPU 110 , HPS 114 , valves (eg, reservoir and / or distributor valves), and / or other aspects of system 100 to supply the desired flow of hydraulic fluid 122 to test station 102 .

[0071] Figure 2is 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 generate 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.

[0072] 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 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.

[0073] 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. A cooling system (not shown) can be employed by the HPU 110 to cool the motor 134 and other components of the HPU 110.

[0074] In one embodiment, the pumps 130 of one or more of the 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, the pumps 130A and 130B may each have the ability to complement each other to provide improved performance compared to conventional HPUs 110 that utilize a single type of pump.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] Housing 139 may enclose reservoir 136 and pump 130, such as Figure 2 As instructed.

[0079] 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.

[0080] 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.

[0081] 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 of the HPUs 110 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 .

[0082] 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 primary streams 106 (e.g., streams 106A and 106B) that are combined by the stream aggregator 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.

[0083] 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 .

[0084] HPS 114 may utilize one or more of pressure sensors 140 to measure the pressure of combined primary flow 150 exiting 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 one or more pressure sensors 140 located downstream of the primary output (such as at the output of the concentrator 148), such as Figure 3 As instructed.

[0085] 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.

[0086] 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.

[0087] Valve 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 drawn into or expelled from the cylinder 164 through its port 176 during a stroke cycle of the piston 162.

[0088] 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.

[0089] The valves 168 may be conventional valves, for example, 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 valves 168 allow 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 4 When 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.

[0090] 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.

[0091] Pump 130B may also take the form of a conventional variable displacement axial pump. Figure 5A 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 a swash plate 186, which operates as a cyclic drive 166. The swash plate 186 drives the cyclic movement of the piston 162 to draw hydraulic fluid into or expel hydraulic fluid from the working volume 170 of the piston pump 160 in response to the movement of the piston pump 160 relative to the swash plate 186. The angle 188 of the swash 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 idle mode to an angle 188 that maximizes the working volume 170 of the piston pump.

[0092] Figure 6 1 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 a synthetic 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).

[0093] Pump 130A may have a fixed displacement 190. Thus, pump 130A lacks the displacement adjuster 178 of pump 130B. Instead, the variable displacement of hydraulic fluid flow 132A produced by pump 130A is controlled by control of active valve 192 by pump controller 193.

[0094] 7A to 7C 1 is a simplified diagram illustrating different operating modes of one of the piston pumps 160 of the pump 130A that are made possible by the active valves 192. The active valves 192 may include a solenoid-operated poppet valve 194 for each piston pump 160 having a first state in which the poppet valve 196 is aligned with the port 176 of the piston pump 160 and blocks hydraulic fluid flow 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 7CThe second state of valve 194 is generally its default (unpowered) state. Active valve 192 may also include a passive valve 199 (e.g., a poppet-type check valve) that allows hydraulic fluid flow from port 176 of piston pump 160 to high pressure port 172 when a pressure threshold is reached, as shown in FIG. Figure 7B shown.

[0095] 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 poppet valve 196 is positioned to prevent fluid flow from traveling to low pressure port 174, 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 Thus, 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 ).

[0096] 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 idle 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.

[0097] Thus, as will be appreciated by those skilled in the art, hydraulic fluid flow 132A exhausted by pump 130A to main port 133 may be controlled based on the number of piston pumps 160 “activated” by setting active valve 194 in the first state and the timing of activation of piston pumps 160 .

[0098] 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 perform various functions described herein in response to executing instructions contained in the memory 204.

[0099] 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 for receiving an input signal 208 (e.g., a sensor signal 100), issuing a control signal 210 (e.g., a signal for controlling a pump, a signal for actuating an active valve, etc.), and / or transmitting data 212, such as in response to executing instructions stored in the memory 204 by the one or more processors 202.

[0100] 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 improved responsiveness to the need for changes in 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 hydraulic fluid output flow 132A by adjusting the number of piston pumps 160 that are activated through the state of the active valve 194 and the control of the timing of activation. 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 in the output flow 132B relative to the time required to make a similar change in the output flow 132A by the pump 130A. For example, the response time of pump 130A (eg, 50 milliseconds) may be approximately one-tenth the response time of pump 130B (eg, 2 to 4 seconds).

[0101] Passive valve hydraulic pump 130B generally suffers from higher heat losses and has lower volumetric energy efficiency when operating at idle compared to pump 130A. However, pump 130B has high volumetric efficiency when operating under pressure at approximately 70% or more of its outlet flow capacity.

[0102] 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 primary 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 using pump 130B, such as during steady state conditions, while providing a much faster response to changing flow demands than conventional HPUs by using pump 130A.

[0103] When a test performed by one or more of the 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 the 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.

[0104] In some embodiments, when the pressure indicated by the pressure signal 142 drops below a first pressure set point, one or more of the active valve hydraulic pumps 130A are activated to generate a corresponding flow 132A, and when the pressure indicated by the pressure signal 142 drops below a second pressure set point, one or more of the passive valve hydraulic pumps 130B are activated to generate 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 of the 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.

[0105] 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 (e.g., proportional valves), each remote pressure control valve controlling 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.

[0106] 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%, such as 2 to 3%, less than the second pressure set point. Therefore, when the pressure at the main output 133 is less than the second pressure set point but greater than the first pressure set point, one or more of the passive valve hydraulic pumps 130B attempt to substantially meet the required flow 212 by adjusting the displacement 170 of the piston pump 160 using the displacement regulator 178. In the event that the pump 130B is slow to respond 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 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 in the main flow 106 (line 212) 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 of the one or more pumps 130A is reduced because the pump 130B can take over and generate the majority of the flow 106 through the main output 133 (line 212).

[0107] The first pressure set point may be 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 of the active valve hydraulic pumps 130A attempt to substantially meet the required flow 106 by activating one or more of the piston pumps 160. In the event that the pump 130A cannot meet the demand for the 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 of the 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 of the one or more pumps 130B decreases because the pump 130A takes over and generates most of the flow 106 through the main output 133.

[0108] 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.

[0109] Fig. 9 1 is a schematic diagram of an example of a test station 102 according to an embodiment of the present disclosure. As described above, the test station 102 includes a plurality of hydraulic actuators 104, such as hydraulic actuators 104A-D, which are configured to apply force and / or drive motion to the test object 103. Each of the hydraulic actuators 104A-D is driven by a corresponding flow portion 122A-D of a hydraulic fluid flow 122, which is driven by a hydraulic power unit 110 ( Figure 1 ) is generated by one or more of the following.

[0110] Each test station 102 may include a test station controller 220 that may take Figure 8 20. The test station controller 220 is generally configured to perform tests on the test object 103 based on, for example, a test program executed (e.g., stored in the memory 204) using one or more processors 202. The test station controller 220 uses the hydraulic fluid flow 122 supplied by one or more of the hydraulic power units 110 and valves (not shown) to control the actuators 104, and in response to the execution of the test program, the hydraulic actuators 104 are used to apply force and / or motion to the test object 103 in a conventional manner.

[0111] During execution of the test, the hydraulic fluid flow 122 varies in response to the varying operation of the actuator 104. Thus, each time the test is performed, the pattern of flow 122 is repeated.

[0112] Embodiments of the present disclosure include methods of controlling a hydraulic power unit based on a pattern, or test flow profile, of flow 122 supplied to a test station 102 during a testing operation.

[0113] In some embodiments, each test flow profile is obtained by measuring the volumetric flow rate (hereinafter referred to as "flow rate") of the hydraulic fluid flow 122 to a given test station 102 during the execution of the test. Therefore, each measured test flow profile corresponds to the flow pattern of the flow 122 during the execution of the test. The test flow profile can then be used during future executions of the test to control the activation and deactivation of the hydraulic pumps 130 of one or more hydraulic power units 110 responsible for supplying the hydraulic fluid flow 122 during the execution of the test.

[0114] For example, instead of activating all hydraulic pumps 130 during the entire test execution, only different subsets of hydraulic pumps 130 may be activated as needed to provide the required fluid flow 122. Thus, when the required hydraulic fluid flow 122 during the test does not require activation of all hydraulic pumps 130, only the subset of hydraulic pumps 130 required to provide the required fluid flow 122 may be activated, while the other hydraulic pumps 130 may be deactivated. This not only significantly saves energy, but also avoids unnecessary wear and tear on the hydraulic pumps 130 and other components of the system 100.

[0115] In some embodiments, the system 100 includes one or more flow meters 224 for use in Figure 1 and Fig. 9 The flow rate of the stream 122 passing through each test station 102 is measured as indicated in Figure 1 As shown in , the system 100 may include: a flow meter 224A located at the flow input of each test station 102 for measuring the flow rate of the hydraulic fluid flow 122, and / or a flow meter 224B located at the flow output of each test station 102 for measuring the flow rate of the hydraulic fluid flow 228 discharged from each test station 102, which are substantially equal to the corresponding input fluid flow 122.

[0116] The flow meter 224C may be used to measure the flow rate of the hydraulic fluid flow 106 discharged from the hydraulic power unit 110, and / or the flow meter 224D may be used to measure the flow rate of the hydraulic fluid flow returning to the hydraulic power unit 110. The flow rates measured by the flow meters 224C and / or 224D may indicate the flow rate of the hydraulic fluid flow 122 to one or more test stations 102 during the execution of one or more tests.

[0117] In one embodiment, flow meter 224E can be used as follows: Fig. 9 The flow rate of the hydraulic fluid flow (eg, flows 122A-D) to each actuator 104 is measured as indicated in . Here, the flow rate of the input hydraulic fluid flow 122 or the output hydraulic fluid flow 228 may be determined by summing the flow rates measured by the flow meter 224E.

[0118] Fig.102 is a graph illustrating a test flow profile 230 according to an embodiment of the present disclosure. The test flow profile 230 represents a time-varying flow rate 232 (grey line) of the inlet flow 122 (and the outlet flow 224) during a given test that has been measured using one or more of the flow meters 224 described above during a previous test.

[0119] Test flow profile 230 may take any suitable form. For example, test flow profile 230 may reflect flow 232 measured over time. Alternatively, test flow profile 230 may generally follow the following: Fig.10 The test flow profile 230 may also be represented by Δ values ​​at different times (e.g., at times t1, t2, t3, etc.) indicating changes in the flow 232 or changes in the profile 234. Other forms of the test flow profile 230 may also be used.

[0120] Fig.11 1 is a flow chart illustrating a method of controlling a hydraulic power unit 110 using at least one controller to generate a variable primary flow 106 for driving a hydraulic actuator 104 of at least one test station 102 during the execution of at least one test according to an embodiment of the present disclosure. The controller may take the form of a system controller 126, a hydraulic power unit controller 128, a test station controller 220, and / or another controller of the system 100. Hereinafter, the controller will be referred to as the hydraulic power unit controller 128.

[0121] At 240 , at least one test flow pattern 230 is obtained. As discussed above, each test flow pattern 230 determines an estimate of a hydraulic fluid flow demand of flow 122 to test station 102 over time corresponding to execution of a test performed by test station 102 .

[0122] In one example, each test station controller 220 may notify the hydraulic power unit controller 128 of the start of a given test or a future start of a test. The hydraulic power unit controller 128 obtains the test flow pattern corresponding to the notification, such as from its memory 204. The notification from each test station 102 may include: an identification of the test station 102, which may be mapped to one of the test flow patterns 230; or an identification of the test to be performed. The hydraulic power unit controller 128 may use this information to obtain the corresponding test flow pattern 230. These notifications may take any suitable form, such as an electrical signal, a data communication, or other type of notification.

[0123] At 242 of the method, the hydraulic power unit 110 is controlled to generate a variable main flow 106 of hydraulic fluid using a plurality of unique subsets of the hydraulic pumps 130 during execution of at least one test. Each unique subset is selected based on at least one test flow profile 230. Thus, the test flow profiles 230 of one or more tests are used to determine different subsets of the plurality of hydraulic pumps 130 of one or more hydraulic power units 110 that will be activated and / or deactivated over time to supply a main flow 106 that satisfies the flow demand 122 of one or more tests being executed by one or more test stations 102.

[0124] In some embodiments, the flow threshold ( Fig.10 ) is used to determine a unique subset of hydraulic pumps 130 that are used in step 242 to satisfy the estimated flow demand 122 of the test station 102 presented in the flow pattern 230. Since each pump 130 is configured to supply up to a maximum flow portion 132 of the primary flow 106, a single pump 130 may be activated to supply flow portions 132 totaling up to a first flow threshold 244A, two of the pumps 130 may be activated to supply flow portions 132 totaling up to a second flow threshold 244B, three of the pumps 130 may be activated to supply flow portions 132 totaling up to a third flow threshold 244C, and so on for additional flow thresholds 244, such as Fig.10 In step 242, pumps 130 that are not needed to meet the estimated flow demands indicated in the test flow profile 230 for the test or tests being performed may be placed in a deactivated state by the controller 128.

[0125] The start-up state of each pump 130 generally corresponds to a state in which the pump 130 is ready to contribute significantly to the variable main flow 106 or to produce a flow portion 132 that contributes significantly (e.g., greater than 3%) to the main flow 106 during step 242. In one embodiment, the pump 130 is placed in the start-up state when the motor 134 of the pump 130 is in the start-up state, in which the motor is powered and drives the operation of the pump 130.

[0126] In one embodiment, the pump 130 is in the deactivated state when the motor 134 of the pump 130 is in the deactivated state where it is not powered.

[0127] Alternatively, the deactivated state of the pump 130 may correspond to an idle state in which the motor 134 is activated, but any flow portion 132 produced by the pump 130 does not contribute significantly (e.g., greater than 3%) to the main flow 106. For example, the active valve hydraulic pump 130A ( Figure 6) can be set to a deactivated state by controlling the active valve 192 to direct the flow of hydraulic fluid to the low pressure port 174 when the corresponding motor 134 is activated, and the passive valve hydraulic pump 130B ( Figure 4 ) can be set to a deactivated state using a working volume regulator 178 to set the flow portion 132 to a minimum value that does not significantly contribute to the main flow 106 when the corresponding motor 134 is activated.

[0128] The flow thresholds 244 may be determined based on the type of hydraulic pump 130 (e.g., 130A or 130B) and its flow capacity. In some embodiments, the flow thresholds 244 include a buffer zone such that the flow thresholds 244 span a range of flows and are generally less than the flow generating capacity of the corresponding hydraulic pump 130. For example, if the pumps 130 each have a flow generating capacity of 100 gallons per minute, the flow thresholds 244 may be, for example, spaced at 90 gallons per minute intervals.

[0129] The flow threshold 244 may be applied to the flow profile 230 to determine the unique subset of hydraulic pumps 130 that are activated during different time periods of the test to drive the primary flow 106 during step 242 to meet the required flow 122 during the execution of the test. When the test flow profile 230 indicates that the current required flow of the flow 122 is between the upper boundary flow threshold and the lower boundary flow threshold 244, the upper boundary flow threshold 244 may be used to determine the unique subset of hydraulic pumps 130 for providing the current required flow 122. Due to the buffer, the sum of the maximum flow portions 132 of the pumps 130 in the unique subset exceeds the flow indicated by the upper boundary flow buffer 244.

[0130] For example, during the time period from t0 to t2, when the flow pattern 230 ( Fig.10 ) is below a first flow threshold (upper flow threshold) 244A for a given test, a first hydraulic pump 130 (e.g., one of the pumps 130A) forming a unique subset of the pumps 130 may be activated in step 242 to supply a flow portion 132 of the desired flow 122 that satisfies the test during that time period. During the time period t0 to t2, other pumps 130 of the hydraulic power unit 110 that are not in the unique subset during that time period may be deactivated because they are not needed to supply the desired flow 122. Thus, for example, when the hydraulic power unit 110 includes six hydraulic pumps 130, such as Figure 2 As shown in FIG. 1 , during the time period t0 to t2 , the subset consisting of the first pump 130 is activated, and the remaining five pumps 130 that are not in the subset are deactivated.

[0131] At time t2, when the estimated required flow rate of the tested flow 122 indicated by the test flow pattern 230 increases to above the first flow threshold (lower flow threshold) 244A and below the second flow threshold (upper flow threshold) 244B, a second hydraulic pump (e.g., one of the pumps 130B) of the hydraulic pumps 130 may be activated to provide an additional flow portion 132 that, when combined with the flow portion 132 provided by the first pump 130, satisfies the estimated required flow rate of the flow 122 indicated by the test flow pattern 230. Thus, a subset of two of the pumps 130 of the hydraulic power unit are activated in step 242 to provide the required flow 122, while the other pumps 130 may be deactivated. Similarly, at time t3, the required flow exceeds the second flow threshold (lower flow threshold) 244B and is lower than the third flow threshold (upper flow threshold) 244C, and the third pump 130 needs to be started to meet the estimated flow demand, thus forming a subset of three pumps 130 that are started in step 242 and drive the flow 122, while the other pumps 130 can remain deactivated.

[0132] Likewise, when the flow profile 230 indicates that the desired flow 122 transitions from being above the lower flow threshold to being below the lower flow threshold, the lower flow threshold becomes the upper flow threshold and is used to determine the subset of pumps 130 needed to drive the desired flow 122. For example, from time t7 to t8, the flow profile 230 indicates that the desired flow 122 is between the upper flow threshold 244E and the lower flow threshold 244D, but at time t8, the estimated desired flow drops below the flow threshold 244D while remaining above the flow threshold 244C. Thus, during the time period from t8 to t9, the flow threshold 244D operates as the upper flow threshold, and the subset of four pumps 130 used to meet the desired flow 122 is determined in step 242. Therefore, the pump 130 corresponding to the flow threshold 244E that was activated during the time period t7 to t8 may be deactivated at or around time t8.

[0133] In some embodiments, the controller 128 transitions the pump 130 from the inactive state to the active state a predetermined time period before the pump 130 is included in the activation subset for contributing to the variable primary flow 106 and helping to meet the desired flow 122. In some embodiments, the predetermined time period allows the corresponding motor 134 to transition from the inactive state to the active state and begin driving the pump 130 in a manner that they can contribute significantly to the primary flow 106. Examples of the predetermined time period include about 2-6 seconds, such as greater than about 3 seconds. Other predetermined time periods may be used based on the characteristics of the pump 130 and its motor 134. Therefore, again referring to Fig.10 , the controller 128 may activate the pump 130 corresponding to the flow threshold 244B within a predetermined period of time before time t2 so that the pump 130 is ready to contribute to the main flow 106 and help meet the required flow 122 at or around time t2.

[0134] In some embodiments, the hydraulic power unit 110 may provide a primary flow 106 that is used to supply the desired flow 122 for multiple tests performed by the test station 102, which flows may sometimes overlap. In such cases, the hydraulic power unit controller 128 aggregates the test flow patterns 230 of the tests during the overlapping time periods to determine the only subset of hydraulic pumps 130 that will be activated to produce a variable primary flow 106 that satisfies the desired flow 122 during those time periods.

[0135] An example of this is in Fig.12 , which includes a chart illustrating an example of a pair of test flow patterns 230A and 230B corresponding to a first test and a second test, respectively, and the operation of the hydraulic power unit 110 during the test execution according to an embodiment of the present disclosure. In some embodiments, the test station 102 executing the first test notifies the hydraulic power unit controller 128 that the first test is started, and the controller 128 obtains (step 240) the test flow pattern 230A corresponding to the first test. The test station 102 executing the second test notifies the hydraulic power unit controller 128 that the second test is started, and the controller 128 obtains (step 240) the test flow pattern 230B corresponding to the second test.

[0136] Since the test flow profile 230A indicates that the test requires a flow 122 below the first flow threshold 244A at time t1, the controller 128 activates the first pump 130 corresponding to the first flow threshold 244A, such as a predetermined period of time before time t1, and uses the first pump 130 to produce a flow portion 132 that forms the main flow 106 and satisfies the estimated required flow indicated by the test flow profile 230A. Likewise, the controller activates the second pump 130 corresponding to the second flow threshold 244B to produce a flow portion 132 at time t2 that contributes to the flow portion 132 of the first pump 130, thereby producing a main flow 106 that satisfies the increased flow indicated at time t2.

[0137] The second test begins at time t3. Therefore, the main flow 106 must satisfy the required flow 122 of the test station 102 performing the first test and the required flow 122 of the test station 102 performing the second test. Therefore, the controller 128 aggregates the test flow patterns 230A and 230B to form an aggregated test flow pattern 230C that controls the operation of the hydraulic power unit 110. Since at time t3, the sum of the estimated required flows indicated by the aggregated test flow pattern 230C remains below the second flow threshold 244B, no change in the activated pump 130 is required. However, at time t4, the increase in the estimated required flow indicated by the test flow pattern 230A causes the aggregated estimated required flow of the profile 230C to exceed the second flow threshold 244B. Therefore, the third pump 130 is activated by the controller 128 to ensure that the main flow 106 accommodates the total required flow for performing the first and second tests during the time period from t4 to t5. Similarly, the controller 128 activates the additional pump 130 at times t5 and t6.

[0138] At time t7, the estimated required flow indicated by the test flow pattern 230C transitions from above the third flow threshold 244C to below the third flow threshold 244C, and therefore, one of the pumps 130 in the subset that was used to drive the primary flow 106 during the time period from t6 to t7 is deactivated, leaving the subset of three pumps 130 to drive the primary flow 106 and supply the required flow 122 of the test station 102 at time t7 or during the time period from time t7 to t8. At time t9 when the second test is completed and at time t10 when the first test is completed 10 Make similar adjustments.

[0139] This process may be used to supply a primary flow 106 that satisfies a desired flow 122 for a plurality of test stations 102 each performing a test for which a test flow profile 230 has been established by measurements of the flow 122 during an earlier performance of the test.

[0140] In some embodiments, when the hydraulic power unit 110 includes both an active valve hydraulic pump 130A and a passive valve hydraulic pump 130B, one of the active valve hydraulic pumps 130A is selected to meet the first flow threshold 244A due to its ability to quickly change its flow portion 132 to match the rapid change in the desired flow 122. Each of the higher flow thresholds 244 can be matched to one of the other active valve hydraulic pumps 130A or one of the passive valve hydraulic pumps 130B that generally operate to provide a flow portion 132 that meets the overall desired flow 122.

[0141] Each hydraulic pump 130 of the unit 110 may be matched to one of the flow thresholds 244 that trigger activation and deactivation of the hydraulic pump by the hydraulic power unit controller 128 based on one or more factors associated with the other hydraulic pumps 130 of the unit 110. These factors may include, for example, the age of the hydraulic pump 130, the total operating time of the hydraulic pump 130 (e.g., hours used), the time since the last activation of the pump 130, and / or other factors. Accordingly, embodiments of the present disclosure include using the hydraulic power unit controller 128 to assign the pumps 130 of the hydraulic power unit 110 to the flow thresholds 244 based on a weighting of one or more of these factors.

[0142] It may be desirable to reduce the use of the oldest and / or longest operating hydraulic pumps 130 of the unit 110 in an effort to reduce wear and tear on the pumps 130 and extend their useful life. Thus, in one embodiment, pumps 130 that are older or have a longer total operating time are weighted toward higher flow thresholds 244, and pumps 130 that are younger or have a shorter total operating time are weighted toward lower flow thresholds 244. This tends to cause the older or longer operating pumps 130 to be assigned to higher flow thresholds 244 where they are activated less frequently than if they were assigned to lower flow thresholds 244. The age and / or operating time of the pumps 130 may be monitored and maintained in the memory 204 of the hydraulic power unit controller 128 and / or the system controller 126 using conventional techniques.

[0143] The last activation time may be used to reduce the activation frequency of the most recently activated pumps 130. This may help spread the use of the hydraulic pumps 130 more evenly. For example, the most recently activated pumps 130 may be weighted toward higher flow thresholds 244 than pumps 130 that have not been activated recently. This tends to cause the most recently activated pumps 130 to be assigned to higher flow thresholds 244 where the pumps will have a lower activation frequency, and tends to assign pumps 130 that have not been activated recently to lower flow thresholds 244 where they are more likely to be activated. Conventional techniques may be used to monitor the time since each pump 130 was last activated by the hydraulic power unit controller 128 and / or the system controller 126 and maintain it in the memory 204.

[0144] Additional embodiments of the present disclosure relate to methods of activating and / or deactivating a hydraulic pump 130. Conventional hydraulic power units 110 typically operate a variable displacement hydraulic pump having a displacement regulator 176 (e.g., a swash plate 186) in an open or closed state. That is, the motor 134 of the pump 130 is activated and drives the pump 130 to full pressure immediately upon activation, and the pump 130 immediately attempts to drive the flow portion 132 based on its pressure set point to form the main flow 106. The sudden activation and deactivation of the motor 134 produces undesirable rapid electrical power changes that generate electrical spikes and exert strain on pump components (e.g., bearings). Additionally, when the newly started pump 130 reaches an operating pressure at which it begins to generate flow portions 132 that contribute to the main flow 106 output by the hydraulic power unit 110, undesirable pressure oscillations may form in the main output flow 106 about the pressure set point of the pump 130, thereby inducing oscillations in the displacement regulator 178, such as oscillations in the angular orientation of the swash plate 186, thereby generating oscillating flow portions 132 that contribute to unstable pressures of the main flow 106.

[0145] Some embodiments of the present disclosure relate to a way to control the transition of a variable displacement hydraulic pump 130 of a hydraulic power unit 110 between an activated state and a deactivated state to avoid electrical spikes and pressure oscillations in a main flow 106. The unit 110 can be formed according to one or more embodiments described herein. For example, the hydraulic power unit 110 includes: a reservoir 136; a main output 133 through which the main flow 106 is discharged; a pressure sensor 140, whose pressure signal 142 indicates the main pressure of the main flow 106; and a plurality of variable displacement hydraulic pumps 130, such as an active valve hydraulic pump 130A and / or a passive valve hydraulic pump 130B.

[0146] Each pump 130 includes a plurality of piston pumps 160, a motor 134 having an activated state in which the motor drives a cyclic variation of the displacement of each piston pump 160, and an inactivated (e.g., unpowered) state. As discussed above, each pump 130 has a pressure set point, and when the main pressure drops below the pressure set point, the pump 130 operates to produce a flow portion 132 that contributes to the main flow 106, and when the main pressure is above the pressure set point, the pump 130 does not operate to generate a flow portion 132 that contributes to the main flow. For example, the main pressure may be in the range of 2500-3500 psi.

[0147] The pumps 130 may have adjustable pressure set points that may be set to different values ​​using, for example, a proportional valve as discussed above, via control signals from the hydraulic power unit controller 128. In some embodiments, the controller 128 adjusts the pressure set points of the pumps 130 as they transition from an inactive state to an active state or vice versa to reduce electrical power spikes, strain on components of the pumps 130, and pressure oscillations of the main flow 106.

[0148] In some embodiments, the pressure set point of each pump 130 is adjustable between values ​​within a range of inoperable pressure set points and values ​​of an operable pressure set point. The inoperable pressure set points represent pressure values ​​below the expected operating range of the main pressure at which the pump 130 does not produce a flow portion 132 that significantly contributes to the main flow 106. For example, the inoperable pressure set points may be within a range of a minimum pressure set point (e.g., 200 psi) to about 93% of the expected operating range of the main pressure, such as 30%-90% of the expected operating range of the main pressure.

[0149] The operable pressure set point corresponds to a value within the expected operating range of the main pressure, such that when the main pressure drops below the operable pressure set point, the pump 130 can produce a flow portion 132 that contributes to the main flow 106. Thus, the operable pressure set point typically corresponds to a conventional pressure set point for the pump 130, such as, for example, 95-99% of the expected operating range of the main pressure.

[0150] Fig.13 is a flow chart illustrating a method of controlling one of the pumps 130 of the hydraulic power unit according to an embodiment of the present disclosure. Fig.14 and Fig.15 is a diagram according to an embodiment of the method Fig.13 Graph of an example of a method of adjusting a pressure set point of a pump 130 over time to transition the pump between an activated state and a deactivated state.

[0151] At 250 of the method, the pump 130 is operated for a predetermined period of time 252 (time t1 to t2), and the pressure set point of the pump 130 is set as Fig.14 254. Thus, in some embodiments of step 250, the hydraulic power unit controller 128 sets the pressure set point of the pump 130 to a value within the range of the inoperable pressure set point 254, such as, for example, 50% of the expected operating range of the main pressure.

[0152] The predetermined time period 252 is set to a value that allows the pump 130 to gradually transition from the deactivated state to the activated state at time t2 without driving the flow portion 132 that contributes significantly (e.g., greater than 3%) to the main flow 106, which may include transitioning the motor 134 from the deactivated state to the activated state. Thus, during the predetermined time period 252, the pump 130 does not interfere with the main flow 106 or contribute to pressure oscillations in the main flow 106. Additionally, since the pump 130 does not attempt to drive the flow portion 132 at the main flow pressure, large transient power spikes and strain on components of the pump 130 are avoided.

[0153] The predetermined time period 252 can be selected to ensure that the motor 134 drives the circulation drive 166 to the desired operating speed (e.g., 1800 rpm) before time t2 and allows the pump 130 to be pressurized to the inoperable pressure set point PS1. In some embodiments, the predetermined time period 252 is about 1-6 seconds, such as, for example, about 4-5 seconds or 3 seconds.

[0154] At 256 of the method, at time t2, pump 130 is operated while the pressure set point is set to a value within the operable pressure set point range 258, which is determined by Fig.14 In some embodiments of step 256, for example, at time t2, the hydraulic power unit controller 128 sets the pressure set point of the pump 130 to a value within the range of operable pressure set points 258, such as 98% of the expected operating range of the main pressure. Thus, the pump 130 transitions to a fully activated state in which the pump is configured to produce a flow portion 132 that contributes significantly to the main flow 106.

[0155] In some embodiments of step 256, the pump 130 is transitioned from the deactivated state to the activated state through multiple stages (e.g., 2-5 stages), wherein the pump 130 is operated at progressively higher inoperable pressure set points. Fig.15 Diagram illustration of .

[0156] For example, when the pump 130 is transitioned from the deactivated state to the activated state at time t1, the pressure set point of the pump 130 is initially set to the non-operable pressure set point PS1, and the operation corresponds to a predetermined time period 252A of the first stage (time t1 to t2). At time t2, the pressure set point of the pump 130 is adjusted to a non-operable pressure set point PS2 that is greater than the non-operable pressure set point PS1, and the operation corresponds to a predetermined time period 252B of the second stage (time t2 to t3). For example, the non-operable pressure set point PS1 can be set to 5%-35% of the expected operating range of the main pressure (e.g., 200-1000 psi), and the non-operable pressure set point PS2 can be set between the pressure set point PS1 and the operable pressure set point PS3, such as 50-80% of the expected operating range of the main pressure (e.g., 1500-2400 psi). Additional stages of operating the pump 130 at the non-operable pressure set point can be added as needed. Thus, the pump 130 is transitioned from the deactivated state to the activated state at a predetermined time period 252A (time t1 to t2). Fig.14 The example transitions to the startup state more gradually.

[0157] In some embodiments, predetermined time period 252A is substantially equal to (eg, + / - 5%), greater than, or less than predetermined time period 252B. In some embodiments, the motor reaches its full operating speed during predetermined time period 252A or during predetermined time period 252B.

[0158] Fig.13 The method may also be performed to gradually transition the pump 130 from the activated state to the deactivated state. Here, step 256 is performed before step 250, such as Fig.14 The transition at time t3 in Fig.15 This gradual deactivation of pump 130 may be as indicated by the transition at time t4 in FIG. Fig.14 occurs within a single phase and a predetermined time period 260, or as indicated in Fig.15 As indicated in FIG. 2 , the process occurs over multiple phases and time periods 260A and 260B.

[0159] Thus, when the pump 130 is operated in the startup state, in the startup state, the motor 134 operates at full speed and the pump 130 is set to the operating pressure set point (e.g., Fig.14 PS2 and Fig.15 The pressure set point of the pump 130 is reduced to one of these inoperable pressure set points. For example, the pressure set point of the pump 130 may be Fig.14 The pressure is reduced to the inoperable pressure set point PS1 at time t3 and Fig.15The initial deactivation phase starting at time t4 in the embodiment of the present invention reduces the pressure to the inoperable pressure set point PS2. This prevents the pump 130 from generating a flow portion 132 that contributes significantly to the main flow 106. Additional deactivation phases (e.g., 2-5) may be used as shown in FIG. Fig.15 The pump 130 is more gradually transitioned to a fully deactivated state as indicated in .

[0160] The one or more predetermined time periods 260 during which the pump 130 operates at the inoperable pressure set point may be set as desired. Fig.14 In the example shown, the motor 134 may be deactivated (power terminated) at the beginning of the deactivation phase, such as at time t3, during the time period 260, or after time t4. Fig.15 When there are multiple deactivation stages as shown in , the motor 134 can be deactivated at the beginning of the initial deactivation stage (time t4), deactivated during the initial deactivation stage (e.g., time period 260A), gradually deactivated throughout all deactivation stages (e.g., time periods 260A and 260B), or deactivated during or after the final deactivation stage (e.g., time period 260B).

[0161] When the pump 130 is a passive valve variable hydraulic pump 130B, the displacement regulator 178 may be shifted to a minimum or idle setting during a single or initial deactivation phase, during all deactivation phases, or during a final deactivation phase.

[0162] Fig.14 and Fig.15 The gradual deactivation of the pump 130 shown in may reduce electrical power transients, pressure oscillations of the primary flow 106 , and strain on components of the pump 130 .

[0163] 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 method of controlling a hydraulic power unit of a dynamic test system using at least one controller, the hydraulic power unit comprising a plurality of hydraulic pumps configured to generate a variable primary flow of hydraulic fluid for driving hydraulic actuators of at least one test station during the performance of at least one test, the method comprising: obtaining at least one test flow profile, each test flow profile identifying an estimate of hydraulic fluid flow demand over time corresponding to performance of one of the at least one test; as well as The variable primary flow of hydraulic fluid is generated using a plurality of unique subsets of the hydraulic pumps during execution of the at least one test, each unique subset being selected based on the at least one test flow pattern.

2. The method according to claim 1, wherein: The method includes identifying, for each of a plurality of time periods, based on the at least one test flow pattern, a corresponding unique subset of the unique subset of hydraulic pumps required to produce a primary flow exceeding a sum of hydraulic fluid flow demand estimates corresponding to the time period; as well as Generating the variable primary flow includes generating the variable primary flow using the identified corresponding unique subset of the hydraulic pumps during each of the plurality of time periods.

3. The method according to claim 2, wherein: During each of the plurality of time periods, a corresponding sum of the hydraulic fluid flow demand estimates is between a lower boundary flow threshold and an upper boundary flow threshold of a plurality of flow thresholds; each flow threshold corresponds to one of said unique subset of said hydraulic pumps; as well as For each time period, identifying the corresponding one of the unique subsets of the hydraulic pumps includes identifying the corresponding one of the unique subsets based on the upflow threshold.

4. The method according to claim 2, wherein: Each of the hydraulic pumps includes an activated state in which the hydraulic pump contributes significantly to the variable primary flow and a deactivated state in which the hydraulic pump does not contribute significantly to the variable primary flow; as well as For at least one of the time periods, generating the variable primary flow includes transitioning one or more of the hydraulic pumps in the corresponding unique subset from the deactivated state to the activated state.

5. The method according to claim 4, wherein: Transitioning one or more of the hydraulic pumps in the corresponding unique subset from the deactivated state to the activated state occurs a predetermined time period prior to the start of the at least one of the time periods.

6. The method according to claim 4, wherein: Each hydraulic pump includes a motor having an activated state in which the motor is powered and drives the hydraulic pump and an inactivated state in which the motor is not powered; as well as Transitioning one or more of the hydraulic pumps in the determined subset from the deactivated state to the activated state includes transitioning a motor of the one or more hydraulic pumps from the deactivated state to the activated state.

7. The method according to claim 1, wherein: The hydraulic power unit comprises: a reservoir containing a hydraulic fluid; a main output through which the variable main flow of hydraulic fluid is discharged; and The plurality of hydraulic pumps include at least one active valve hydraulic pump having a variable displacement and at least one passive valve hydraulic pump having a variable displacement.

8. The method according to claim 7, wherein: Each subset includes one of the at least one active valve hydraulic pumps.

9. The method according to claim 8, 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 piston pumps and configured to place the piston pump in an activated state in which cyclic changes in the working volume drive at least a portion of the variable primary flow 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 configured to control each of the active valves to individually set the 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 piston pumps, each piston pump configured to draw hydraulic fluid through the low pressure port and into an adjustable working volume and to drive at least 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 piston pump.

10. The method according to claim 1, wherein: Obtaining at least one test flow pattern includes measuring at least one hydraulic fluid flow during a previous execution of the at least one test.

11. A dynamic testing system, comprising: at least one test station, each test station configured to apply force and / or displacement to a test object using a hydraulic actuator during performance of a test; a hydraulic power unit including a plurality of hydraulic pumps configured to generate a variable primary flow of hydraulic fluid that drives a hydraulic actuator of the at least one test station during performance of at least one test; as well as At least one controller, the at least one controller being configured to: obtaining at least one test flow profile, each test flow profile identifying an estimate of hydraulic fluid flow demand over time corresponding to performance of one of the at least one test; as well as The variable primary flow of hydraulic fluid is generated using a plurality of unique subsets of the plurality of hydraulic pumps during execution of the at least one test, each unique subset being selected based on the at least one test flow pattern.

12. The system according to claim 11, wherein: The at least one controller is configured to: identifying, for each of a plurality of time periods, a corresponding unique subset of the unique subset of hydraulic pumps required to produce a primary flow in excess of a sum of hydraulic fluid flow demand estimates corresponding to the time period based on the at least one test flow pattern; as well as The variable primary flow is generated using the identified corresponding unique subset of the hydraulic pumps during each of the plurality of time periods.

13. The system according to claim 12, wherein: During each of the plurality of time periods, a corresponding sum of the hydraulic fluid flow demand estimates is between a lower boundary flow threshold and an upper boundary flow threshold of a plurality of flow thresholds; each flow threshold corresponds to one of said unique subset of said hydraulic pumps; as well as For each time period, the corresponding one of the unique subsets of the hydraulic pumps is identified based on the upflow threshold.

14. The system according to claim 12, wherein: Each of the hydraulic pumps includes an activated state in which the hydraulic pump contributes significantly to the variable primary flow and a deactivated state in which the hydraulic pump does not contribute significantly to the variable primary flow; as well as For at least one of the time periods, one or more of the hydraulic pumps in the corresponding unique subset are transitioned from the deactivated state to the activated state to generate the variable primary flow.

15. The system of claim 14, wherein: For at least one of the time periods, one or more of the hydraulic pumps in the corresponding unique subset are transitioned from the deactivated state to the activated state a predetermined time period before the start of the at least one of the time periods to generate the variable main flow.

16. The system of claim 14, wherein: Each hydraulic pump includes a motor having an activated state in which the motor is powered and drives the hydraulic pump and an inactivated state in which the motor is not powered; as well as The one or more hydraulic pumps in the determined subset are transitioned from the deactivated state to the activated state by transitioning a motor of the one or more hydraulic pumps in the determined subset from the deactivated state to the activated state.

17. The system of claim 11, wherein: The hydraulic power unit comprises: a reservoir containing a hydraulic fluid; a main output through which the variable main flow of hydraulic fluid is discharged; and The plurality of hydraulic pumps include at least one active valve hydraulic pump having a variable displacement and at least one passive valve hydraulic pump having a variable displacement.

18. The system of claim 17, wherein: Each subset includes one of the at least one active valve hydraulic pumps.

19. The system of claim 18, 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 piston pumps and configured to place the piston pump in an activated state in which cyclic changes in the working volume drive at least a portion of the variable primary flow 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 configured to control each of the active valves to individually set the 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 piston pumps, each piston pump configured to draw hydraulic fluid through the low pressure port and into an adjustable working volume and to drive at least 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 piston pump.

20. A method of controlling a hydraulic power unit of a dynamic testing system using at least one controller, the 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 main pressure of the main flow; a plurality of variable displacement hydraulic pumps, each variable displacement hydraulic pump being configured to drive a portion of the main flow, each variable displacement hydraulic pump comprising: Multiple piston pumps; a motor having an activated state and a deactivated state, wherein the motor drives a cyclic change in the displacement of each piston pump in the activated state; and Pressure set point, the pressure set point is selectable between: an inoperable pressure set point range below the expected operating range of the main pressure, at which the variable displacement hydraulic pump does not contribute to the main flow; and an operable pressure set point within an expected operating range of the main pressure, wherein the variable displacement hydraulic pump is driven to contribute to the main flow, The method includes controlling one of the variable displacement hydraulic pumps, including: operating the variable displacement hydraulic pump for a first predetermined period of time while the pressure set point is set to a first inoperable pressure set point within the inoperable pressure set point range; and The variable displacement hydraulic pump is operated when the pressure set point is set to the operable pressure set point.

21. The method according to claim 20, wherein: Operating the variable displacement hydraulic pump for the first predetermined period of time occurs before operating the variable displacement hydraulic pump when the pressure set point is set to the operable pressure set point.

22. The method according to claim 21, wherein: Operating the variable displacement hydraulic pump for the first predetermined period includes transitioning the motor from the deactivated state to the activated state.

23. The method according to claim 22, wherein: After operating the variable displacement hydraulic pump for a first predetermined period of time and before operating the variable displacement hydraulic pump when the pressure set point is set to the operable pressure set point: operating the variable displacement hydraulic pump for a second predetermined period of time while the pressure set point is set to a second inoperable pressure set point within the inoperable pressure set point range; and The second pressure set point is higher than the first pressure set point.

24. The method according to claim 20, wherein: Operating the variable displacement hydraulic pump for the first predetermined period of time occurs after operating the variable displacement hydraulic pump when the pressure set point is set to the operable pressure set point.

25. The method of claim 24, operating the variable displacement hydraulic pump for the first predetermined period of time comprises transitioning the motor from the activated state to the deactivated state.

26. The method of claim 25, wherein: After operating the variable displacement hydraulic pump while setting the pressure set point to the operable pressure set point and before operating the variable displacement hydraulic pump for a first predetermined period of time: operating the variable displacement hydraulic pump for a second predetermined period of time while the pressure set point is set to a second inoperable pressure set point within the inoperable pressure set point range; and The second pressure set point is higher than the first pressure set point.

27. The method according to claim 20, wherein: Operating the variable displacement hydraulic pump for the first predetermined period of time includes setting the pressure set point to the first inoperable pressure set point using a controller; and Operating the variable displacement hydraulic pump when the pressure set point is set to one of the operable pressure set points includes using the controller to set the pressure set point to the operable pressure set point.

Images