CONTROLLED LOAD ABORT IN AN ACTUATOR SYSTEM

A method for unloading a load on a test article in a testing system includes determining a load differential in at least one of a calculated load at a valve for an actuator of the testing system and a calculated load on a load cell coupled to the actuator. A controlled unload of the load on the test article is initiated via a system controller when the determined load differential a reaches a first level. An interlock unload of the load on the test article is performed via the valve when the determined load differential reaches a second level higher than the first level.

BACKGROUND

In testing systems, test articles under test are very expensive, and it is necessary to quickly and effectively reduce loading on the test article in certain situations so as to prevent damage to the test article.

SUMMARY

In one aspect, a method for unloading a load on a test article in a testing system includes determining a load differential in at least one of a calculated load at a valve for an actuator of the testing system and a calculated load on a load cell coupled to the actuator. A controlled unload of the load on the test article is initiated via a system controller when the determined load differential reaches a first level. An interlock unload of the load on the test article is performed via the valve when the determined load differential reaches a second level higher than the first level.

In some embodiments, the commands to the valve are issued through the system controller.

Determining the load differential can be performed numerous ways and may include comparing a calculated load at the valve to a calculated load at the load cell, or determining the load differential may include determining load values for two outputs of the load cell, and assigning the load differential as a difference between the load values for the two outputs of the load cell, or determining the load differential may include comparing a calculated load at the valve to a commanded load at the valve, or determining the load differential may include comparing a load value output of the load cell to a commanded load at the valve. In some embodiments, determining the load differential is performed continuously during a flow mode of the testing system.

In some embodiments, initiating the controlled unload via the system controller may include unloading during a flow mode of the testing system to unload the load differential to a benign load differential.

Performing the interlock unload may include: isolating the valve from a source of hydraulic power of the testing system; taking measurements of pressures on a piston of the actuator; determining a load differential on opposite sides of a piston of the hydraulic actuator coupled to the valve; and ramping the load differential to a benign load differential using the valve.

Taking measurements of pressures on the piston may occur a predetermined delay time after isolating the valve.

If desired, ramping the load differential can be performed over a predetermined time period, and also if desired, ramping the load differential can be performed linearly over the predetermined time period.

In another aspect, a method of interlock unloading a test article in a test system with a valve controlling an actuator includes isolating the valve from a hydraulic source of the test system, and determining a load differential on opposite sides of a piston of the hydraulic actuator coupled to the valve. Then, the load differential is ramped to a benign load differential using the valve.

In some embodiments, the method and may include delaying a predetermined time between isolating and determining the load differential. If desired, ramping the load differential can be performed over a predetermined time period, and also if desired, ramping the load differential can be performed linearly over the predetermined time period. Determining the load differential can be performed using any of the methods indicated above.

In yet another aspect, a system for monitoring and unloading a load on a test article includes a hydraulic assembly and a controller. The hydraulic assembly incudes a control valve configured to control loads in a hydraulic actuator coupled to the test article, a pair of pressure transducers configured to detect and transmit pressures in the hydraulic actuator, and an isolation valve to isolate the control valve from hydraulic pressure. The controller is configured to determine a load differential in at least one of a calculated load at a valve for an actuator of the testing system and a calculated load on a load cell coupled to the actuator. A controlled unload of the load on the test article is initiated via a system controller when the determined load differential a reaches a first level. An interlock unload of the load on the test article is performed via the valve when the determined load differential reaches a second level higher than the first level.

In some embodiments, the testing system where the valve further may include a controller to receive the pressures, and valve firmware configured to reduce differential load on a piston of the hydraulic actuator. The valve firmware can be configured to perform an interlock unload of the load on the test article by: isolating the valve from a hydraulic source of the testing system; determining a load differential on a piston of the actuator coupled to the valve; and ramping the load differential to a benign load differential using the valve. Determining the load differential can be performed using any of the methods indicated above.

The valve firmware can be further configured to delay a predetermined time between isolating and determining the load differential. If desired, the valve firmware is further configured to ramp the load differential over a predetermined time period. If further desired, the valve firmware is configured to ramp the load differential linearly over the predetermined time period.

In some embodiments, the testing system and may include a power controller coupled between the controller and the hydraulic assembly to control power supplied to the valve and the hydraulic assembly, to receive and transmit signals indicative of loads on the hydraulic actuator and valve, and to receive and transmit commands from the controller.

In still another aspect, a hydraulic assembly includes a proportional valve configured to control a hydraulic actuator. The proportional valve has a controller to receive pressures indicative of a load on a test article, and the proportional valve operates valve firmware configured to reduce differential load on a piston of the hydraulic actuator.

In some embodiments, the hydraulic assembly may include a pair of pressure transducers configured to detect and transmit pressures at the hydraulic actuator to the proportional valve.

The valve firmware can be configured to perform an interlock unload of the differential load by: isolating the proportional valve from a source of hydraulic power to the hydraulic assembly; taking measurements of pressures on a piston of the actuator; determining a load differential on the piston of the hydraulic actuator; and ramping the load differential to a benign load differential using the valve. Determining the load differential can be performed using any of the methods indicated above.

In some embodiments, the valve firmware is further configured to take measurements of pressures on the piston a predetermined delay time after isolating the valve. If desired, the valve firmware is further configured to ramp the load differential over a predetermined time period. If further desired, the valve firmware is configured to ramp the load differential linearly over the predetermined time period.

The hydraulic assembly may include an isolation valve to isolate the proportional valve from the source of hydraulic power.

This summary is not intended to describe each disclosed embodiment or every implementation of controlled load abort as described herein. Many other novel advantages, features, and relationships will become apparent as this description proceeds. The figures and the description that follow more particularly exemplify illustrative embodiments.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

FIG.1illustrates a system100for monitoring and unloading a load on a test article. System100comprises in one embodiment a hydraulic assembly110and a system controller130. Hydraulic assembly110comprises in one embodiment a control valve112configured to control loads in a hydraulic actuator120coupled to the test article. Hydraulic assembly110further comprises a pair of pressure transducers114which are configured to detect and transmit pressures in the hydraulic actuator120. An isolation valve116is provided to selectively isolate the control valve112from a hydraulic source140of hydraulic pressure. In such a case, the control valve112can then locally reduce the load of the actuator120upon the test article pursuant to instructions executed by a local processor in the control valve without further direction from the system controller130.

The system controller130in one embodiment is configured to determine a load differential in at least one of a calculated load at the control valve112for a hydraulic actuator120of the testing system100and a calculated load on a load cell122coupled to the hydraulic actuator. In a first method to unload the load on the test article by each actuator connected thereto, the system controller130is further configured to initiate a controlled unload of the load on the test article via the system controller130when the determined load differential reaches a first level. This controlled unload is done during a flow mode of the system, that is, when hydraulic source140is coupled to the system100and valve operation of each control valve112is controlled by the system controller130. This first level may be referred to as a stop level. Should the stop level controlled unload not work, the controller130is further configured to perform an interlock unload of the load on the test article via commands sent to each control valve112of each actuator120needed to unload the loads on the test article when the determined differential load reaches a second level, higher than the first level, at which point a valve controlled unload, or interlock unload, is used to unload the load on the test article.

In one embodiment, the control valve112further comprises a local valve controller113to receive the pressures from the pressure transducers114, and valve firmware115operable by the local controller113and configured to reduce differential load on a piston of the hydraulic actuator120. The unloading of the load of the actuator by execution of the firmware115by the local valve controller113to control operation of its associated actuator120, in one embodiment, is performed without further input from the system controller130. The control valve112is shown in greater detail inFIG.2.

The firmware115is in one embodiment configured to perform an interlock unload of the load on the test article. Generally, this is accomplished in one embodiment by isolating the control valve112from the hydraulic source140via operation of the isolation valve116, (which can be initiated by the system controller130or in the alternative from the local controller113executing firmware115). The local controller113determines a load differential on a piston124of the hydraulic actuator120coupled to the control valve112, and operates the control valve112to ramp the load differential to a benign load differential using the control valve112. This is done in an interlock situation by the control valve112alone, operating the firmware115, upon receipt of an interlock unload command issued by the system controller130.

System controller130is in one embodiment an external controller that runs software for operating the testing system100based on a testing procedure in a system computer131that provides a user interface to a user for configuration, operation and monitoring of the testing of the test article.

The firmware115of control valve112is designed to operate the control valve112independently of the system controller130to properly and safely ramp the load differential on a test article to a benign load differential. Test articles can be very expensive pieces of equipment with values in the millions of dollars. As used herein a “benign load differential” is a load differential upon the test article from the one or more actuators connected thereto that a test engineer considers is safe from any damage to the test article. Hence, some loading may exist upon the test article in a “benign load differential” state from one or more actuators but damage of the test article is not likely. A “benign load differential” may also be a load differential that does not provide any non-representative loading of the test article in the testing system.

In the testing system100, multiple control valves112may be connected to multiple hydraulic actuators120that provide load to various positions or portions of a test article. In the exemplary embodiment illustrated inFIG.3, a series of eight hydraulic actuators1201,1202, . . . ,1208is shown, in which the hydraulic actuators1201,1202, . . . ,1208are each controlled by a hydraulic assembly1101,1102, . . . ,1108. The load cell122of each hydraulic actuator120is configured to provide load signals to the system controller130. The pressure sensors114and the control valve112are also configured to provide load signals to the system controller130. An isolation valve116is typically provided for each control valve120. The system controller130controls operation of each isolation valve116and control valve112under “flow mode” when the test article is under test pursuant to a desired testing procedure.

The local firmware115of each control valve112in one embodiment is further configured to delay a predetermined time between isolating the hydraulic assembly110from the hydraulic source140and determining the load differential. This is done to allow a settling of the pressures following the isolation. The local firmware115is further configured in one embodiment to ramp the load differential over a predetermined time period. The predetermined time period may be programmed into the firmware115of the control valve112such as at set up. This ramp time may be adjusted by reprogramming the local firmware115. The ramping of the load differential over the predetermined time period is in one embodiment performed linearly over the predetermined time period; however, it should not be considered limiting. Rather, unloading via a linear ramp is but one embodiment in that operation of each valve112by the local processor113pursuant to local firmware115of the valve can perform unloading pursuant to a non-linear ramp using the measured pressures from the pressure transducers114measuring cylinder pressures on each side of the actuator piston. Control valve112in one embodiment is a proportional valve.

The system100in one embodiment further comprises a power controller150coupled between the system controller130and the hydraulic assembly110. The power controller150is operable to control power supplied to each control valve112and each isolation valve116of each hydraulic assembly110controlling each actuator120, to receive and transmit signals indicative of loads on each hydraulic actuator120and each control valve112, and to receive and transmit commands from the system controller130for loading the test article, and/or unloading the test article either as a controlled stop unload (under the control of the system controller130with command signals sent to each valve control112) or as an interlock unload at each actuator120(under the control of the local processor113executing the local firmware115on control valve112). Signals to and from power controller150from and to system controller130are carried in communication lines152, which may be wired, wireless, or a combination thereof.

Referring now toFIG.2, a hydraulic assembly110is schematically illustrated and comprises the control valve112configured to control a hydraulic actuator such as120. The control valve112is in one embodiment a proportional valve that has its own local controller113and local firmware115loaded therein to control operation of the control valve112during an interlock unload operation.

The hydraulic assembly110further comprises in one embodiment a pair of pressure transducers114(one for each port of the actuator120) configured to detect pressures on opposite sides of the piston in each actuator and transmit signals indicative of measured pressures at the hydraulic actuator120. The control valve112controller113is configured to receive the measured pressures which are indicative of a load on a test article. The control valve112in one embodiment operates local valve firmware115as discussed above, which is configured to remove differential load on the piston of the hydraulic actuator in an interlock unload situation, typically to the benign load differential for each associated actuator120.

As discussed above, the local firmware115is configured in one embodiment to perform an interlock unload of the differential load that exists across the piston of the associated actuator. This is performed in one embodiment by isolating the control valve112from the hydraulic source140of hydraulic power to the hydraulic assembly110. Following isolation, measurements of pressures on a piston such as piston124of an actuator such as hydraulic actuator120are made such as from pressure transducers114. A load differential on the piston124of the hydraulic actuator120is determined, and the load differential is ramped to the benign load differential using the control valve112. As has been discussed, the operation of the control valve112is, for an interlock unload, independent, and relies on its local controller113and firmware115to ramp the load differential to a benign load differential rather than under the supervision or control of the system controller130, other than to initiate the interlock unload.

As has been discussed, the local firmware115, in one embodiment, is further configured to take measurements of hydraulic pressures on opposite sides of the piston a predetermined delay time after isolating the control valve112. The local firmware115is further configured to ramp the load differential existing on each associated actuator120over the predetermined time, and to do so, for example, linearly. In one embodiment, the hydraulic assembly110further comprises an isolation valve116used to isolate the control valve112from the source140of hydraulic power. In one embodiment, isolation valve116is a solenoid valve.

In normal operating conditions, the testing system100will have hydraulic pressure provided to actuators120by hydraulic source140. The testing system100may have many hydraulic actuators120, each coupled to the hydraulic source140through a manifold or other hydraulic distribution system. In one embodiment, the testing system100comprises a plurality of testing sub-systems, each sub-system comprising a plurality of hydraulic actuators. In one embodiment, each sub-system comprises eight hydraulic actuators120each having an associated control valve112and isolation valve116, and has associated connections through power controller150, which contains a power supply for the sub-system, and the ability to relay valve and actuator information to the system controller130. In one embodiment, system controller130is a testing system controller such as a Flex Test 200 Controller manufactured by MTS Systems Corporation of Eden Prairie, Minnesota, USA.

The testing system100mitigates risk of non-representative loading or loading that can damage the test article being tested by the testing system100in several ways. There is a calculated load from the control valves112of the sub-system fed to the system controller130through the power controller150. The system controller130determines potential load differentials from one or more actuators120that may not be operating correctly in various ways, as described further herein. If there is a possible test article load differential, then the system controller130can initiate a controlled unload, referred to above as a stop level or just “stop situation”. In the stop situation, the system controller130is under control and uses normal operation in the testing system hydraulics to reduce the load differential while the hydraulic power is still provided. Failure of certain components in the testing system100may trigger a stop, or controlled unload, as is known in the art. However, monitoring of the pressure transducers and calculated and commanded loads on components of the testing system100, and/or measured loads from associated load cells122, may also result in the system controller130issuing a stop command.

In the event that a stop command is unsuccessful, that is, the load differential upon the test article is not being reduced or mitigated, that indicates a potential problem with the integrity of the system controller130or of the control loop of the testing system100to perform the stop command. In this situation, or if the load differential continues to increase to a second, higher level beyond the stop level, an interlock is ordered by the system controller130for one or more of the actuators120, although commonly the command is initiated for all of the actuators120. In a traditional interlock, non-representational or uneven unloading of a load on a test article may occur, potentially leading to damage to the test article. In embodiments of the present disclosure, an interlock results in a controlled, for example, linear unloading of load differential on the test article through the use of the control valves112as controlled by each local processor113, which in an interlock condition, operate entirely on their own after receiving the interlock command. Local firmware115executed by each local processor113controls the unloading of the load differential to a benign load differential without the use of the system controller130, typically other than initiating the interlock commands to each control valve112.

Referring toFIG.3, a sub-system of eight hydraulic assemblies1101,1102, . . . ,1108is shown. Each hydraulic assembly1101,1102, . . . ,1108is coupled to a manifold or the like of hydraulic source140, to its own hydraulic actuator1201,1202, . . . ,1208, and to a power controller150over communication lines152. The load cells1221,1222, . . . ,1228are coupled to each associated actuator1201,1202, . . . ,1208and the test article300so as to transmit the load from each actuator120. It should be noted each load cell1221,1222, . . . ,1228can provide one or more, for example, two signals indicative of the measured load thereon to the system controller130. The control valves112of the hydraulic assemblies1101,1102, . . . ,1108are coupled to hydraulic source140and to power controller150, and receive instructions from the system controller130therethrough so as to execute the desired loading upon the test article300in normal operation, execute a stop situation as described above, or initiate an interlock unloading at each actuator1201,1202, . . . ,1208via its associated control valve112. On interlock, each valves of the hydraulic assemblies1101,1102, . . . ,1108are isolated from the hydraulic source140and operate independently according to their local firmware115to ramp the load differential on their respective load cells/actuators to a benign load differential.

A representative design of one hydraulic assembly110configuration is shown inFIGS.4A and4B. Hydraulic assembly110is configured with a manifold118to which hydraulic lines may be connected. Control valve112, pressure transducers114, and isolation valve116are mounted to the manifold118in one embodiment. Isolation valve116in one embodiment is enabled by a solenoid.

FIG.5shows a hydraulic circuit500that is used for the provision of hydraulic power to the control valve112and hydraulic actuator120. Hydraulic source140has pressure and return lines142and144providing hydraulic fluid to and from each control valve112. Isolation valve116isolates the pressure line142, and hence the hydraulic source140, from the control valve112, pressure transducers114, and hydraulic actuator120on initiation of an interlock unload. In one embodiment, isolation valve is enabled with a solenoid. Once the isolation valve116isolates the control valve112, transducers114, and hydraulic actuator120, local firmware115executing on local processor113in the control valve112determines the load differential existing in the associated actuator120, and operates to ramp the load differential to a benign load differential for that actuator120without further input from a system controller130. Check valves502,504, and506assist in regulating or controlling pressures in the hydraulic system500.

A method600for unloading a load on a test article in a testing system is shown in flow chart600inFIG.6. Method600comprises determining the existence of possible test article load differential in at least one of a calculated load at a valve for an actuator of the testing system and a calculated load on a load cell coupled to the actuator in block602, or other situation that requires the stop situation to be executed by the system controller130. With respect to undesired loading on the test article, the method600further comprises initiating a controlled unload of the load on the test article via the system controller when the determined load differential reaches a first level in block604. This first level may be referred to as a stop level or stop situation. A stop situation initiates the controlled unload of the load on the test article using the system controller. However, in the event the controlled unload via the system controller130executing in the stop situation is considered unsatisfactory, at block606, an interlock unload of the load on the test article is performed via each valve of each actuator when the determined load differential reaches a second level, higher than the first level, after which a valve controlled unload, or interlock unload, is used to unload the load on the test article. Commands to each valve are in one embodiment issued through the system controller130.

There are a number of potential load differential determinations that may be used in order to determine first level and correction first level for a stop, and a second load differential level for an interlock. The existence of a possible undesired load differential in the test article can be determined or ascertained using one or more different criteria. In one embodiment, determination comprises comparing a command load (desired from the actuator) as controlled by the associated valve to a measured load from the associated loadcell. In another embodiment, determining the load differential comprises determining whether load values for two outputs of the load cell as described above are different, and assigning the determined load differential as a difference between the load values for the two outputs of the load cell. In another embodiment, determining a load differential exists comprises comparing a calculated load at the valve to a commanded load at the valve. And in yet another embodiment, determining the load differential comprises comparing a load value output of the load cell to a commanded load at the valve.

Determining the load differential is performed in one embodiment continuously during a flow mode of the testing system, i.e., during normal operation of the test system100so as to conduct the desired test upon the test article. Each of the potential load differentials may be monitored, and a load differential on any of the methods that reaches the first, stop, level triggers a controlled unload stop situation via commands issued by the system controller130in response to the determined load differential. When a stop, or controlled unload, does not lower the load differential and the load differential rises to a second level higher than the first level, an interlock unload is commanded by the system controller130. Performing an interlock unload at each of one or more actuators120(commonly all actuators) comprises in one embodiment isolating each control valve112from the source of hydraulic power140of the testing system, and taking measurements of pressures on opposite sides of the piston of the actuator120, for example, via the pressure transducers114coupled to each port of the actuator120. The load differential across the piston is determined, and is ramped to a benign load differential using the control valve112under the control of the local processor113executing the local firmware115. Taking measurements of pressures on the piston occurs in one embodiment after a predetermined delay time following isolation of the valve so that the loading upon the test article120can be properly ascertained. Ramping of the load differential is performed in one embodiment over a predetermined time period, and in one embodiment is performed linearly over the predetermined time period.

Interlock unloading of the test article in a test system is performed according to method700which is shown inFIG.7. Method700pertains to the operation of each hydraulic circuit500given the interlock command from the system controller130. The method comprises isolating the control valve112from a hydraulic source140of the test system in block702, in one embodiment by operation of isolation valve116, and determining a load differential on opposite sides of a piston of the actuator coupled to the valve in block704. The load differential is ramped to a benign load differential using the valve in block706. The method700may further comprise delaying a predetermined time between isolating and determining the load differential. It should also be noted that typically, the initial load differential existing for each actuator as measured by the pressure transducers114is saved in memory at the control valve112and used by the local processor113executing the local firmware115. The initial pressures are used to ascertain the load differential desired during ramping to the benign load differential. The measured pressures from pressure transducers114are continually received by the local processor so that the control valve112is controlled to achieve the desired decreases in the load differential during the unloading. Ramping of the load differential, as has been discussed, may be done over a predetermined time, and may, for example, be performed linearly over the predetermined time period. It should be noted, in one embodiment, the predetermined delay and the predetermined time period is substantially the same for all actuators120coupled to the test article. This can be advantageous for even though each control valve112is operating independently, the loads from the actuators120are each being reduced beginning at substantially at the same time and at a percentage rate pursuant to the stored unloading instructions in the local firmware115. Therefore, the unloading upon the entirety of the test article occurs in a somewhat balanced manner across the test article so as to reduce the possibility of damage to the test article during unloading.

Embodiments of the present disclosure therefore provide methods and systems for controlled unload of load differential on a test article in a testing system upon load differential reaching a first, stop level, and safe linear interlock unloading should the load differential reach a second higher, interlock level.