PNEUMATIC GRIP SYSTEM AND MATERIAL TESTING SYSTEM EQUIPPED WITH PNEUMATIC GRIP SYSTEM

Abstract

An exemplary materials testing system includes pneumatic grips configured to grip a specimen to be tested based on an applied pressure; and a processor configured to control the pressure applied to the pneumatic grips by repeatedly controlling a fill valve to increase the applied pressure, stabilizing the applied pressure after each increase, and adjusting the time of pressurization based on comparing the expected pressure increase to the actual pressure increase during pressurization.

Description

[Technical field]

[0001] [Related Applications] This application claims the benefit of U.S. Patent Application No. 17 / 170,170, filed February 8, 2021, entitled "PNEUMATIC GRIP SYSTEMS AND MATERIAL TESTING SYSTEMS INCLUDING PNEUMATIC GRIP SYSTEMS," and U.S. Provisional Patent Application No. 62 / 972,054, filed February 9, 2020, entitled "PNEUMATIC GRIP SYSTEMS AND MATERIAL TESTING SYSTEMS INCLUDING PNEUMATIC GRIP SYSTEMS." The entireties of U.S. Patent Application No. 17 / 170,170 and U.S. Provisional Patent Application No. 62 / 972,054 are incorporated herein by reference. [Background technology]

[0002] This disclosure relates generally to materials testing, and more particularly to pneumatic grip systems and materials testing systems including pneumatic grip systems.

[0003] Universal testing machines are used to perform mechanical tests, for example compressive strength tests or tensile strength tests, on materials or components. Summary of the Invention

[0004] A pneumatic grip system and a materials testing system including the pneumatic grip system are disclosed substantially as illustrated and described with reference to at least one of the drawings and as more fully set forth in the claims. [Brief description of the drawings]

[0005] These and other features, aspects, and advantages of the present disclosure will be better understood when the following detailed description is read in conjunction with the accompanying drawings, in which like reference characters represent like parts throughout.

[0006] [Figure 1] FIG. 1 is a diagram of an example testing device for performing mechanical property tests, according to aspects of the present disclosure. [Diagram 2] 2 is a block diagram of an exemplary implementation of the test device of FIG. 1. [Diagram 3] FIG. 3 is a block diagram of an exemplary embodiment of the safety system of FIG. 2. [Figure 4A] 4 is a flow chart representing example machine readable instructions that may be executed by the safety processor of FIG. 3 to control the state of the materials testing system of FIGS. 1-3. [Figure 4B] 4 is a flow chart representing example machine readable instructions that may be executed by the safety processor of FIG. 3 to control the state of the materials testing system of FIGS. 1-3. [Diagram 5] FIG. 4 illustrates an example operator interface that can be used to implement the operator interfaces of FIGS. 1-3. [Figure 6] FIG. 4 illustrates another example operator interface that can be used to implement the operator interface of FIGS. 1-3. [Figure 7] 7 illustrates the example materials testing system of FIG. 1 and the operator interface of FIGS. 5 and 6 during a start-up routine of the materials testing system. [Figure 8] 7 illustrates the example materials testing system of FIG. 1 in a materials testing system setup state and the operator interface of FIGS. 5 and 6. FIG. [Figure 9] 7 illustrates the example materials testing system of FIG. 1 and the operator interface of FIGS. 5 and 6 while jogging the crosshead with limited motion in a setup state. FIG. [Figure 10] 7 illustrates the example materials testing system of FIG. 1 and the operator interface of FIGS. 5 and 6 while jogging the crosshead with reduced constraints in an attention or test state. [Figure 11] 7 illustrates the example materials testing system of FIG. 1 and the operator interface of FIGS. 5 and 6 while controlling actuation of the pneumatic grips with limited actuation in a setup state. [Figure 12] 7 illustrates the example materials testing system of FIG. 1 and the operator interface of FIGS. 5 and 6 while controlling actuation of pneumatic grips with reduced limits in a caution or test state. [Figure 13A] 7 illustrates the example materials testing system of FIG. 1 and the operator interface of FIGS. 5 and 6 while progressing from a SETUP state to a CAUTION state and a TEST state to begin a materials test. [Figure 13B] 7 illustrates the example materials testing system of FIG. 1 and the operator interface of FIGS. 5 and 6 while progressing from a SETUP state to a CAUTION state and a TEST state to begin a materials test. [Figure 13C] 7 illustrates the example materials testing system of FIG. 1 and the operator interface of FIGS. 5 and 6 while progressing from a SETUP state to a CAUTION state and a TEST state to begin a materials test. [Figure 14A] 7 illustrates the example materials testing system of FIG. 1 and the operator interface of FIGS. 5 and 6 while progressing from a setup state to a caution state and a test state to return the crosshead to the desired state. [Figure 14B] 7 illustrates the example materials testing system of FIG. 1 and the operator interface of FIGS. 5 and 6 while progressing from a setup state to a caution state and a test state to return the crosshead to the desired state. [Figure 14C] 7 illustrates the example materials testing system of FIG. 1 and the operator interface of FIGS. 5 and 6 while progressing from a setup state to a caution state and a test state to return the crosshead to the desired state. [Figure 15] FIG. 4 is a block diagram of an example pneumatic grip system that can be used to implement a portion of the safety system of FIG. 3. [Figure 16A] 1 is a graph showing manifold pressure and grip pressure during a conventional pneumatic grip pressurization process. [Figure 16B] 4 is a graph illustrating manifold pressure and grip pressure during an exemplary disclosed pneumatic grip pressurization process.

[0007] The drawings are not necessarily to scale and, where appropriate, like or identical reference numbers are used to refer to like or identical components. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Conventional material testing systems use mitigation techniques such as configuration switches, guarding, force limiting controls, motion limits, and / or protection to improve operator safety. However, conventional material testing systems often do not fully comply with international standards. Conventional mitigation techniques require the operator to place the system in an appropriate operating mode, such as safe interaction or test. Many conventional safety techniques can be implemented using off-the-shelf safety components, such as programmable logic controllers (PLCs) and / or relays. PLCs and relays typically add significant cost to a material testing system.

[0009] An exemplary material testing system disclosed includes a pneumatic grip configured to grip a specimen to be tested based on an applied pressure, and a processor configured to control the pressure applied to the pneumatic grip by repeatedly controlling a fill valve to increase the applied pressure, stabilizing the applied pressure after each increase, and adjusting the time of pressurization during pressurization based on comparing an expected pressure increase to an actual pressure increase.

[0010] In some example materials testing systems, the pneumatic grip comprises a first grip and a second grip, and the processor is configured to control pressure supplied to the pneumatic grip by controlling pressure to at least one of the first grip or the second grip. Some example materials testing systems further comprise a second fill valve, the fill valve configured to control gas flow from a gas supply to the second fill valve, and the second fill valve configured to control gas flow from the fill valve to the first grip.

[0011] In some example materials testing systems, the processor is configured to control the second fill valve to selectively increase the pressure, maintain the pressure, or release the pressure via an exhaust. Some example materials testing systems further include a third fill valve configured to control gas flow from the fill valve to the second grip. In some example materials testing systems, the processor is configured to stabilize the delivered pressure after each increase by closing the fill valve and the second fill valve.

[0012] Some example material testing systems further include a release valve configured to vent pressure from the pneumatic grip. In some example material testing systems, the fill valve includes a first solenoid and the release valve includes a second solenoid, and the processor is configured to control the first solenoid and the second solenoid to have a default state configured to release pressure from the pneumatic grip. In some example material testing systems, the processor is configured to determine that the delivered pressure has stabilized based on a rate of change of the pressure. In some example material testing systems, the processor is configured to determine that the delivered pressure has stabilized when the rate of change of the pressure is less than a threshold rate.

[0013] An exemplary method of controlling a pneumatic device in a materials testing system is disclosed herein, the method including controlling, with a processor, the pressure supplied to a pneumatic device of the materials testing system by repeatedly, via the processor, controlling a fill valve to increase the supplied pressure, stabilizing the supplied pressure after each increase, and, during pressurization, adjusting the time of pressurization based on comparing an expected pressure increase to an actual pressure increase.

[0014] In some example methods, the pneumatic grip includes a first grip and a second grip, and controlling the pressure supplied to the pneumatic grip includes controlling the pressure to at least one of the first grip or the second grip. In some example methods, controlling the fill valve to increase the supplied pressure includes controlling a gas flow from a gas supply to the second fill valve and controlling the second fill valve to control the gas flow from the fill valve to the first grip.

[0015] Some example methods further include controlling the second fill valve to selectively increase the pressure, maintain the pressure, or release the pressure via an exhaust. In some example methods, controlling the fill valve to increase the delivered pressure includes controlling gas flow from the fill valve to the second grip by controlling a third fill valve. In some example methods, stabilizing the delivered pressure includes closing the fill valve and the second fill valve.

[0016] Some example methods further include controlling a release valve to vent pressure from the pneumatic grip. In some example methods, the fill valve comprises a first solenoid and the release valve comprises a second solenoid, and the method further includes controlling the first solenoid and the second solenoid to have a default state configured to release pressure from the pneumatic grip. Some example methods further include determining that the delivered pressure has stabilized based on a rate of change of the pressure. In some example methods, determining that the delivered pressure has stabilized is in response to determining that the rate of change of the pressure is less than a threshold rate.

[0017] The disclosed exemplary materials testing system incorporates or integrates a safety system within the materials testing system that complies with international standards. Because the safety system is integrated within the materials testing system, the disclosed exemplary materials testing system provides improved safety and at a much lower cost than would be achieved using off-the-shelf components, because the safety system is integrated within the materials testing system's existing electronics, semiconductors, and / or circuit boards. Integration further improves reliability, thereby reducing or eliminating external wiring between purchased safety components.

[0018] As described in more detail below, the disclosed example safety system of the material testing system includes a machine status indicator that visually indicates the status of the testing machine in terms of operational limits. The disclosed example safety system of the material testing system provides high reliability and an activation mechanism that is monitored at the machine control points that may include internal fault checking and / or power diagnostics within the material testing system. In some examples, pneumatic grips are provided with two-stage grip pressure control and monitoring. The disclosed example material testing system is compatible with interlocked guard systems having redundant or distinct contacts. Such guard systems comply with ISO safety standards by using redundant, distinct, and / or dynamic real-time monitoring. The disclosed example material testing system includes redundant crosshead travel limit monitoring. The disclosed example material testing system shutdown circuitry complies with international safety standards including ISO 13849-1.

[0019] Additionally, conventional off-the-shelf safety relay components used with PLCs use an extra layer of firmware in the PLC to stop motion of moving components during an emergency stop event. The disclosed example safety system of a materials testing system is configured to allow hardware (e.g., an emergency stop button) to directly shut down the power amplifier drive to the actuator(s), regardless of whether the embedded firmware in the safety processor is operational.

[0020] Disabling of the circuitry, actuators, and / or other hardware may be accomplished via hardware, software (including firmware), or a combination of hardware and software, and may include physical disconnection, de-energization, and / or software controls that limit commands from being implemented to activate the circuitry, actuators, and / or other hardware. Similarly, enabling of the circuitry, actuators, and / or other hardware may be accomplished via hardware, software (including firmware), or a combination of hardware and software, using the same mechanisms used for disabling. Firmware may include stored instructions, such as Safety Rated Embedded Software (SRESW) and / or Safety Rated Application Software (SRASW).

[0021] The disclosed exemplary material testing system complies with the European Machinery Directive following the rules set forth in the ISO 13849-1 standard for "Safety Related Parts of Control Systems." The following functions, identified by a system risk analysis, are incorporated into the material testing system: The safety system provides a passive drive state that removes energy from the driving crosshead, a passive drive state that removes energy from the gripping system, and a limited drive state for operator setup. In the limited drive state, the exemplary safety system monitors the crosshead speed to keep it below an upper speed limit, monitors for intentional manual movement (jog) of the crosshead, monitors for reduced gripping pressure when closing, and / or monitors for intentional grip closure.

[0022] As used herein, "crosshead" refers to a component of a materials testing system that applies directional (axial) and / or rotational forces to a specimen. A materials testing system can have one or more crossheads, and the crosshead(s) can be positioned in any suitable position and / or orientation in the materials testing system.

[0023] The disclosed example materials testing system further includes a non-limit drive state that allows for the removal of checks in the limit drive state. In some examples, the non-limit drive state can be entered via a dual activation mechanism, in which materials testing functions are performed and the operator does not interact with the system.

[0024] The disclosed example materials testing system includes various status indicators, such as an invalid status indicator, a setup status (e.g., constrained drive mode) indicator, a caution status (e.g., non-constrained drive mode) indicator, and a test status (e.g., non-constrained drive mode) indicator on every machine to clearly indicate when an operator can interact and when a hazard exists.

[0025] The disclosed example materials testing systems include one or more stop features configured to override the initiation and / or continuation of motion of components such as the crosshead or grips. Additionally, the one or more stop features can be configured redundantly via hardware such that these stop features are effective to disable the materials testing system even when the software portion of the safety system is disabled. Examples of such stop features that can be included in the disclosed systems include interlocked guards and / or emergency stop switches.

[0026] Some disclosed example materials testing systems include the selection and implementation of a single control point for initiating the materials testing frame and / or gripping system. Some example systems provide power failure monitoring and / or protection to ensure that the system ceases unrestricted operation and places the materials testing system in an inactive drive state once power is restored. In some examples, any pneumatic specimen grippers are automatically de-energized in response to a power failure.

[0027] The disclosed example safety system and materials testing system includes increased internal diagnostics and reporting to the operator of critical errors within the system, such as equipment malfunctions or inconsistencies between redundant inputs, redundant outputs, and / or redundant processes. The disclosed example materials testing system allows for faster removal and / or insertion of specimens than conventional materials testing systems due to a safe setup mode of the testing machine that allows operator operation within the test space without disabling the materials testing system or requiring guard doors. The disclosed example system further improves operator safety due at least in part to the use of a setup state that limits the crosshead movement and / or limited movement and / or force that can be exerted by the grips when setting up and configuring the system within the test space.

[0028] The disclosed materials testing system and safety system can be utilized in the disclosed exemplary configurations to be specifically configured to achieve the identified risk mitigation. The disclosed materials testing system is significantly more efficient than purchasing generic off-the-shelf individual safety components for materials testing.

[0029] The disclosed materials testing systems and safety systems are configured to revert to the restricted state whenever the non-restrictive state is not actively used and / or to require intentional action by an operator to transition from the restricted state to the non-restrictive state. Exemplary materials testing systems and safety systems provide an active warning notification when the non-restrictive state is activated. Exemplary active warning notifications include those defined as notifications that appear and / or disappear in locations where an operator is likely to be making an observation (as opposed to, for example, providing a static label or other static visual indicia on the materials testing system). Additionally, the disclosed exemplary notifications are intuitive, such as by providing a commonly understood color scheme (e.g., green, yellow, red) to communicate the status of the materials testing system.

[0030] 1 illustrates an example material testing system 100 for performing mechanical property tests. The example material testing system 100 can be, for example, a universal testing system capable of static mechanical tests. The material testing system 100 can perform, for example, compressive strength tests, tensile strength tests, shear strength tests, flexural strength tests, flexural strength tests, tear strength tests, peel strength tests (e.g., adhesive bond strength), torsional strength tests, and / or any other compressive and / or tensile tests. Additionally or alternatively, the material testing system 100 can perform dynamic tests.

[0031] The example materials testing system 100 includes a testing apparatus 102 and a computing device 104 communicatively coupled to the testing apparatus 102. The testing apparatus 102 applies a load to a material under test 106 and measures a mechanical property of the test, such as a displacement of the material under test 106 and / or a force applied to the material under test 106. The example testing apparatus 102 is shown as a dual column apparatus, although other apparatuses, such as a single column testing apparatus, may be used.

[0032] The example computing device 104 can be used to configure the test apparatus 102, control the test apparatus 102, and / or receive measurement data (e.g., transducer measurements such as force and displacement) and / or test results (e.g., peak force, break displacement, etc.) from the test apparatus 102 for processing, displaying, reporting, and / or any other desired purpose.

[0033] Figure 2 is a block diagram of an exemplary implementation of the materials testing system 100 of Figure 1. The exemplary materials testing system 100 of Figure 2 includes a test instrument 102 and a computing device 104. The exemplary computing device 104 can be a general purpose computer, a laptop computer, a tablet computer, a mobile device, a server, an all-in-one computer, and / or any other type of computing device.

[0034] The exemplary computing device 104 of FIG. 2 includes a processor 202. The exemplary processor 202 can be any general-purpose central processing unit (CPU) from any manufacturer. In some other examples, the processor 202 can include one or more special-purpose processing units, such as a RISC processor with an ARM core, a graphics processing unit, a digital signal processor, and / or a system on a chip (SoC). The processor 202 executes machine-readable instructions 204, which can be stored locally at the processor (e.g., in an internal cache or on the SoC), in a random access memory 206 (or other volatile memory), in a read-only memory 208 (or other non-volatile memory, such as flash memory), and / or in a mass storage device 210. The exemplary mass storage device 210 can be a hard drive, a solid-state storage drive, a hybrid drive, a RAID array, and / or any other mass data storage device.

[0035] The bus 212 allows communication between the processor 202 , the RAM 206 , the ROM 208 , the mass storage device 210 , the network interface 214 , and / or the input / output interface 216 .

[0036] The example network interface 214 includes hardware, firmware, and / or software that connects the computing device 104 to a communications network 218, such as the Internet. For example, the network interface 214 may include IEEE 202.X compliant wireless and / or wired communications hardware for transmitting and / or receiving communications.

[0037] The example I / O interface 216 of FIG. 2 includes hardware, firmware, and / or software that couples one or more input / output devices 220 to the processor 202 to provide input to and / or output from the processor 202. For example, the I / O interface 216 can include an image processing device that interfaces with a display device, a Universal Serial Bus port that interfaces with one or more USB-compliant devices, FireWire, Fieldbus, and / or any other type of interface. The example materials testing system 100 includes a display device 224 (e.g., an LCD screen) coupled to the I / O interface 216. Other example I / O device(s) 220 can include a keyboard, a keypad, a mouse, a trackball, a pointing device, a microphone, an audio speaker, a display device, an optical media drive, a multi-touch touch screen, a gesture recognition interface, a magnetic media drive, and / or any other type of input and / or output device.

[0038] The example computing device 104 can access non-transitory machine-readable medium 222 via I / O interface 216 and / or I / O device(s) 220. Examples of machine-readable medium 222 in FIG. 2 include optical disks (e.g., compact disks (CDs), digital versatile / video disks (DVDs), Blu-ray Discs®, etc.), magnetic media (e.g., floppy disks®), portable storage media (e.g., portable flash drives, secure digital (SD) cards, etc.), and / or any other type of removable and / or installed machine-readable medium.

[0039] The example materials testing system 100 of Figure 1 further includes a test instrument 102 coupled to a computing device 104. In the example of Figure 2, the test instrument 102 is coupled to the computing device via an I / O interface 216, such as a USB port, a Thunderbolt port, a FireWire (IEEE 1394) port, and / or any other type of serial or parallel data port. In some other examples, the test instrument 102 is coupled to the network interface 214 and / or the I / O interface 216 via a wired or wireless connection (e.g., Ethernet, Wi-Fi, etc.), either directly or via a network 218.

[0040] The testing apparatus 102 of FIG. 2 includes a frame 228, a load cell 230, a displacement transducer 232, a cross-member loader 234, a material fixture 236, a control processor 238, and a safety system 240. The frame 228 provides rigid structural support for the other components of the testing apparatus 102 that perform the tests. The load cell 230 measures the force applied by the cross-member loader 234, via the grips 236, to the material being tested. The cross-member loader 234 applies the force to the material being tested, while the material fixture 236 (also referred to as the grips) grips or otherwise couples the material being tested to the cross-member loader 234. The exemplary cross-member loader 234 includes a motor 242 (or other actuator) and a crosshead 244. A crosshead 244 couples the material fixture 236 to the frame 228, and a motor 242 moves the crosshead relative to the frame to position the material fixture 236 and / or apply forces to the material being tested. Exemplary actuators that can be used to provide force and / or motion to the components of the materials testing system 100 include electric motors, pneumatic actuators, hydraulic actuators, piezoelectric actuators, relays, and / or switches.

[0041] Exemplary grips 236 include compression platens, jaws, or other types of fixtures depending on the mechanical property being tested and / or the material being tested. Grips 236 can be manually configured, controlled via manual input, and / or automatically controlled by control processor 238. Crosshead 244 and grips 236 are operator accessible components.

[0042] The example control processor 238 communicates with the computing device 104, for example, to receive test parameters from the computing device 104 and / or report measurements and / or other results to the computing device 104. For example, the control processor 238 may include one or more communications or I / O interfaces that enable communication with the computing device 104. The control processor 238 may control the cross member loader 234 to increase or decrease the applied force, control the fixture(s) 236 to grip or release the material under test, and / or receive measurements from the displacement transducers 232, load cells 230, and / or other transducers.

[0043] The example safety system 240 provides an additional layer of monitoring and control to the test apparatus 102. The safety system 240 monitors operator inputs and the state of the test apparatus 102. In the example of FIG. 2, the safety system 240 limits the user's operation of the test apparatus 102 such that the test apparatus 102 is controllable by the user only when the machine is in a proper state. In response to detecting one or more conditions, the safety system 240 automatically causes the test apparatus 102 to go into a restricted state (such as a limited setup state that disables all power and movement that may present an unsafe condition).

[0044] As discussed in more detail below, the safety system 240 selectively adds, removes, increases, and / or decreases restrictions on the operation of the material testing system based on monitoring input signals from the material testing system 100, input signals from the safety system 240, and / or control signals from the control processor 238. The safety system 240 controls the operation of the material testing system 100 by determining from a number of predefined states under which the material testing system 100 will be operated at any given time. Exemplary predefined states include one or more restrictive states in which one or more operations of the material testing system 100 are restricted (e.g., disabled, limited, etc.) and one or more non-restrictive states in which restrictions on the restrictive states are reduced and / or removed. In the example of FIG. 2, the safety processor 240 associates with and / or interrupts the control of the cross member loader 234 and / or fixture(s) 236 by the control processor 238. In some other examples, the safety system 240 may directly control the cross member loader 234 and / or the fixture(s) 236 while enforcing any applicable limits on the actuators.

[0045] Exemplary limit states include a setup state and an override state. In the setup state, the safety system 240 limits one or more actuators (e.g., the motor 242 and / or the grip actuator(s) 246) and controls (or allows control of) these actuators in response to operator input. Exemplary limits on the motor 242 and / or the crosshead 244 may include an upper speed limit and / or an upper or lower position limit of the crosshead 244 relative to the test fixture 102. Exemplary limits on the grip actuator(s) 246 may include an upper pressure limit and / or an upper grip force limit. In the override state, the safety system 240 limits the actuators and the control processor 238 does not control the actuators in response to operator input (e.g., does not attempt to control the motor 242 and / or the grip actuator(s) 246 or is prevented from controlling the motor 242 and / or the grip actuator(s) 246 via a power interruption).

[0046] Exemplary non-restrictive states include a caution state and a test state. In an example caution state, the safety system 240 reduces the constraints on the actuators (e.g., motors 242 and / or grip actuator(s) 246) and does not control the actuator(s) motors 242 and / or grip actuator(s) 246. In the caution state, the control processor 238 may control the actuator(s) to perform actions such as a high speed jog of the crosshead 244 and / or an increase in gripping force by the pneumatic grips 248, such that an operator should not be in physical proximity to the crosshead 244 and / or pneumatic grips 248. In an example test state, the safety system 240 reduces the constraints on the actuators and the control processor 238 controls the actuator(s) to perform a test (e.g., according to a material testing procedure or program executed by the control processor 238).

[0047] 2 may further include one or more control panels 250 including a plurality of status indicators 252 and one or more mode switches 254. The mode switches 254 may include buttons, switches, and / or other input devices disposed on the operator control panel. For example, the mode switches 254 may include a button that controls the motors 242 to jog (e.g., position) the crosshead 244 to a particular position on the frame 228, a switch (e.g., a foot switch) that controls the grip actuators 246 to open and close the pneumatic grips 248, a mode control button that is pressed along with another button that enables the safety system 240 to allow operation in an unrestricted state, and / or any other input device that may effect operation in an unrestricted state.

[0048] The status indicators 252 correspond to a set of predefined states (e.g., the disabled, setup, caution, and test states discussed above) that the safety system 240 can set for the materials testing system 100. As described in more detail below, the safety system 240 controls the status indicators 252 to provide an indication as to the current status of the materials testing system 100 as determined by the safety system 240. The status indicators 252 may include lights, displays, audio, mechanical systems, and / or any other indication discernible by an operator.

[0049] Figure 3 is a block diagram of one exemplary embodiment of the safety system 240 of Figure 2. As shown in Figure 3, the safety system 240 includes a safety processor 302.

[0050] The example safety processor 302 includes multiple redundant processing cores 304a, 304b. The processing cores 304a, 304b execute redundant instructions 306a, 306b and receive redundant inputs to generate substantially identical outputs during normal operation of the tester 102. The safety processor 302 monitors the multiple inputs (e.g., via the redundant cores 304a, 304b) and determines a state of the materials testing system 100 based on the inputs. The safety processor 302 can compare the outputs of the redundant instructions 306a, 306b and control a state of the materials testing system 100 based on the comparison of the outputs.

[0051] The example safety processor 302 and / or redundant processing cores 304a, 304b may include a general purpose central processing unit (CPU) from any manufacturer. In some other examples, the safety processor 302 and / or redundant processing cores 304a, 304b may include one or more special purpose processing devices, such as a RISC processor with an ARM core, a graphics processing unit, a digital signal processor, and / or a system on a chip (SoC). The safety processor 302 and / or redundant processing cores 304a, 304b execute machine readable instructions, such as redundant instructions 306a, 306b, which may be stored locally in the processor (e.g., in an internal cache or on the SoC), in a storage device, such as a random access memory, a read only memory, and / or a mass storage device.

[0052] The redundant processing cores 304a, 304b and redundant instructions 306a, 306b allow redundant and / or distinct inputs and outputs to be processed by the safety system 240, thereby providing a highly reliable and predictable system. Thus, while representative inputs and outputs are shown in FIG. 3, these inputs and / or outputs may be replicated to support the redundant processing cores 304a, 304b and redundant instructions 306a, 306b. The redundant instructions 306a, 306b (e.g., embedded software, operating systems, and generated code) executed by the safety processor 302 are compliant with processes outlined in international standards. These international standards include, but are not limited to, ISO 13849-1 for "safety-related parts of control systems." While the illustrated safety processor 302 includes multiple redundant processing cores, in other examples, the safety processor 302 may include a single processing core or multiple non-redundant processing cores.

[0053] The safety system 240 of FIG. 3 further comprises an actuator disable circuit 308 that selectively disables the power amplifier 310 from providing energy to the motor 242 of the crosshead 244. Additionally or alternatively, the actuator disable circuit 308 (or another actuator disable circuit) can disable the grip actuator(s) 246 from providing energy to the pneumatic grip(s) 248. The power amplifier 310 receives input and output power for the motor 242 and controls the movement of the crosshead 244. The example actuator disable circuit 308 and power amplifier 310 can be implemented using a safety compliant Safe Torque Off (STO) high reliability servo power amplifier. The control processor 238 can control the movement of the motor 242 and the crosshead 244 via a motor control signal 312 to the power amplifier 310.

[0054] In response to an STO signal 314 from the safety processor 302, the actuator disable circuit 308 disables the connected actuator (e.g., the motor 242). For example, the actuator disable circuit 308 can disconnect all energy to the motor 242 (and / or other moving parts in the materials testing system 100) for less than a certain defined period of time. The example actuator disable circuit 308 can provide an STO feedback signal 315 to the safety processor 302 that indicates whether the actuator disable circuit 308 is currently disabling an actuator. The safety processor 302 can compare the STO signal 314 to the STO feedback signal 315 to detect a fault.

[0055] In the exemplary material testing system 100, the movement of the moving crosshead 244 and any internal components is stopped after activation of the STO signal 314 as specified by the international standard. Most of the subsystems of the safety system 240 disclosed herein activate the actuator disable circuit 308 to safely stop the machine. In addition, the power amplifier 310 can include a motor braking circuit 316 that slows down the motor 242 before applying the STO signal 314. The motor braking circuit 316 allows the motor 242 to stop in a more controlled manner by eliminating continued movement due to mechanical inertia after the drive power is removed. By using pre-disabling of braking, the movement of the crosshead 244 after the motor 242 is de-energized is reduced or minimized. Thus, the exemplary actuator disable circuit 308 and motor braking circuit 316 provide a Category 1 stop as defined in the IEC 60204-1 standard, "Electrical Safety Standard for Machinery."

[0056] The example safety processor 302 monitors the motor 242 and / or the motor braking circuitry 316 while brake pre-disable is occurring to ensure that the motor 242 is braking. If the safety processor 302 determines that the motor 242 is not decelerating during braking, the safety processor 302 performs brake fault mitigation, which aborts braking and immediately de-energizes the motor 242. By implementing brake fault mitigation on a two-stage override sequence, the safety processor 302 can reduce stopping distances in situations where braking is ineffective. While stopping distances are shortest when brake pre-disable is active, a two-stage sequence with brake pre-disable not active can have a longer stopping distance than a single-stage sequence (e.g., only disconnect) when brake pre-disable is not fully active. A side benefit of brake fault mitigation is that it allows for greater flexibility in implementing the two-stage override sequence in that a wider range of components and systems can be used for high performance braking with the brake fault mitigation process being able to catch brake system faults.

[0057] The example safety system 240 further includes an emergency stop 318 (e.g., a button, switch, etc.) that provides an emergency stop input signal 320 to the safety processor 302. The emergency stop 318 can be a manually operated emergency stop button, which is a complementary safety feature. The emergency stop 318 has two channel redundancy for signaling. The emergency stop 318 can include an emergency stop switch 322, an emergency stop detection circuit 324, and an actuator disable circuit 326. The emergency stop 318 is independently controllable using hardware and embedded software of the safety processor 302. For example, in response to detecting the emergency stop input signal 320 from the emergency stop detector 324, the safety processor 302 sets the state of the materials testing system 100 to a disabled state and provides an emergency stop output signal 321 to the emergency stop 318 (e.g., the emergency stop switch 322).

[0058] The emergency stop switch 322, in response to the emergency stop output signal 321, controls an actuator disable circuit 326 to control the actuator disable circuit 314 and / or the motor braking circuit 314 to stop the motor 242. An example actuator disable circuit 326 may have a first connection to the motor braking circuit 314 and a second, redundant connection to the actuator disable circuit 308. When the actuator disable circuit 326 is triggered, it activates the motor braking circuit 314, implements a delay for a time to allow braking to occur, and then activates the actuator disable circuit 308, de-energizing the applicable actuators.

[0059] In addition to or instead of control via the safety processor 302, the emergency stop switch 322 can directly activate the actuator disable circuit 308 in the power amplifier 310, such as by a physical interruption of an STO signal 314 between the safety processor 302 and the actuator disable circuit 308. The safety processor 302 monitors the emergency stop detection circuit 324 and acts as a redundant monitor of the hardware. When the emergency stop switch 322 is released, the safety processor 302 controls the actuator disable circuit 308 to output the STO signal 314 and continue to disable the motor 242, such that the materials testing system 100 remains in a disabled state (e.g., a restricted state) and requires user interaction to re-enable operation of the motor 242.

[0060] The example material testing system 100 (e.g., the tester 102) is compatible with an interlocked guard system having redundant or different contacts. The example safety system 240 can include one or more guards 328 and guard interlocks 330 configured to provide a physical and / or virtual barrier to operator access to the material testing system 100 while operating in an unrestricted state. For example, the guards 328 can include a physical barrier that is opened and closed to control access to a volume around the pneumatic grips 248 and / or the crosshead 244 (and / or other moving components). The example physical barrier includes a guard door that can monitor whether the door guarding the protected volume is open or closed using redundant safety switches. Each door switch has mechanically linked normally open and normally closed contacts that can be dynamically pulsed (e.g., by the guard interlock 330) and / or otherwise accommodated as an input device. The pulsing allows for a real-time diagnostic check of the plausibility of the guard door switches.

[0061] Additionally or alternatively, guard 328 may include a virtual guard that monitors a volumetric area around pneumatic grip 248 and / or crosshead 244 for intrusion into the volumetric area. Example virtual guards may include light curtains, proximity sensors, and / or pressure pads. Although the virtual guard does not physically impede access, the virtual guard outputs a guard signal to guard interlock 330, which outputs an interlock signal 332 to safety processor 302 and / or actuator disable circuit 308 (e.g., similar to emergency stop switch 322 described above).

[0062] The interlock 330 can trigger the actuator disable circuit 308 to de-energize the motor 242. In some examples, when the guard interlock 330 is no longer triggered, the safety processor 302 controls re-enabling of the power amplifier 310 in a manner similar to the emergency stop switch 322 described above.

[0063] Additionally or alternatively, the example safety system 240 can default to a restricted "setup" state when an operator enters the protected volume of the materials testing system 100. Instead of disabling or de-energizing the actuators of the system 100, this set-up state implements restrictions on speed, pressure, or other activity.

[0064] The example safety system 240 includes a number of status indicators 252 and a mode switch 254. The example safety processor 302 monitors the mode switches 254, for example, by dynamically pulsing the mode switches 254 to generate or obtain mode switch input signals 338 (e.g., one or more mode switch inputs for each of the mode switches 254). In some examples, the mode switches 254 are high reliability switches. The safety processor 302 may test the mode switches 254 for shorts or other fault conditions periodically, aperiodically, in response to an event (e.g., upon start-up of the materials testing machine), based on a predetermined schedule, and / or at any other time.

[0065] The example safety processor 302 controls the status indicators 252 to indicate the status of the materials testing system 100 to an operator. For example, the safety processor 302 can output indicator signals 342 to the status indicators 252. If the status indicators 252 are lights, the output indicator signals 342 can control each of the lights to be, for example, on, off, flashing, and / or any other output state of the light. In some examples, the safety processor 302 determines the status of the indicators via indicator feedback signals 340. The example indicator feedback signals 340 can indicate to the safety processor 302 whether each of the status indicators 252 is on, off, short circuited, open circuited, and / or any other status or state of the indicators 252. If the processor determines that one or more of the status indicators 252 is not in the proper commanded state, the safety processor 302 controls the materials testing system to a restricted state and provides a notification to the operator (e.g., via the control panel 250 or other notification).

[0066] The safety system 240 includes a power supply monitor 344 that monitors the power supplies (e.g., DC and AC power supplies) that provide power to the components of the materials testing system 100. The power supply monitor 344 provides one or more power supply status signals 346 to the safety processor 302 and / or watchdog circuit 362 (described below) that indicate whether the monitored power supplies are within their respective voltage and / or current ranges. If the power supply monitor 344 determines that one or more of the power supplies are outside of the acceptable ranges, the safety processor 302 and / or watchdog circuit 362 can disable the materials testing system 100 and alert an operator.

[0067] The example safety system 240 further comprises one or more speed sensors 348. The example speed sensor(s) 348 can be an integrated speed monitoring sensor, a redundant speed monitoring sensor, and / or different speed monitoring sensors. The speed sensor(s) 348 provide a speed signal(s) 350 representative of the crosshead speed to the safety processor 302. The safety processor 302 monitors the speed signal(s) 350 to ensure that the crosshead 244 does not exceed an upper speed limit (e.g., crosshead travel limit(s) 352) determined by the current operating mode of the machine. For example, the value of the upper speed limit can depend on whether the materials testing system 100 is in a limited or unlimited state. In some examples, two speed sensors operating on different principles can be used in the materials testing system 100 to prevent the sensor 348 from suffering a common cause failure. The speed signal 350 of each speed sensor 348 is read and compared by the safety processor 302 to verify that the speed signals 350 match. If one speed sensor 348 indicates a different speed than another speed sensor 350, the safety processor 302 disables the materials testing system 100 (e.g., via the actuator disable circuit 308).

[0068] Example crosshead travel limit(s) 352 can include a travel limit that specifies a limit on the position of the crosshead 244. When the crosshead travel limit(s) 352 is reached, the safety processor 302 stops movement of the crosshead 244. In some examples, the crosshead travel limit(s) 352 are multi-level limits that indicate how many triggered limits exceed the crosshead travel limit(s) 352. In some examples, a first level limit is handled by the safety processor 302 to stop operation of the applicable actuator (or all actuators), such as the motor 242. If the crosshead 244 continues to move beyond the first level limit and reaches a second level limit (e.g., farther than the first level limit outside the acceptable range), the crosshead travel limit 352 can trigger a direct connection (e.g., a hard connection) to the actuator disable circuit 308 and / or the motor braking circuit 316 and / or the actuator disable circuit 326 to trigger a two-phase disable of the motor 242.

[0069] In some examples where the materials testing system 100 includes automated grippers (e.g., pneumatically powered grips, hydraulically powered grips, electrically powered grips, electromechanically powered grips, electromagnetically powered grips, etc.), the safety system 240 includes a grip controller 354 that controls the grip actuators according to a multi-pressure gripping scheme. The multi-pressure gripping scheme reduces (e.g., minimizes, eliminates) the risk of injury to an operator when placing a material test specimen into the pneumatic grips 248 of the materials testing system 100.

[0070] When the safety processor 302 is controlling the materials testing system 100 in a SETUP state, the safety processor 302 provides a pressure signal 356 to the grip controller 354. The grip controller 354 controls an upper limit on the pressure that can be applied through the grips 248 by controlling the grip actuator(s) 246. The pressure signal 356 (which can be directly proportional to the specimen gripping force) is limited to allow sufficient pressure to grip the specimen through the grips 248, but not enough pressure to cause serious injury to the operator. Conversely, when the safety processor 302 is controlling the materials testing system 100 in a CAUTION state or TEST state, the safety processor 202 provides a pressure signal 356 that causes the grip controller 354 to allow a higher pressure than would be used to grip the test specimen during testing. The example grip controller 354 can monitor the main system pressure (e.g., via pressure sensor(s) 358) and / or monitor the pressure(s) in the pneumatic grip(s) 248 (e.g., upper and lower grips). The grip controller 354 provides a pressure signal 360 to the safety processor 302 to verify that the commanded pressure is being implemented.

[0071] In some examples, the grip controller 354 is controlled via operator input using a foot pedal switch. For example, the foot pedal switch may include separate switches for applying and releasing pressure via the pneumatic grip(s) 248. The switches may be mechanically linked switches that can be dynamically pulsed to check plausibility between the switches and / or monitor for potential faults (e.g., electrical faults) within the switches.

[0072] The safety processor 302 further controls the grip controller 354 to de-energize the grip actuator(s) 246 when power to the materials testing system 100 is disabled. For example, the safety processor 302 may control the grip actuator(s) 246 (e.g., via one or more valves, relays, etc.) to allow pressurization when powered, but, in the case of a pneumatic actuator, to be normally depressurized such that the pneumatic grip(s) 248 are prevented from applying a gripping force when the materials testing system 100 is not powered.

[0073] The example safety system 240 further comprises a watchdog circuit 362. The watchdog circuit 362 communicates with the safety processor 302 periodically, aperiodically, in response to one or more events or triggers, and / or at any other time to verify the operation of the safety processor 302. For example, the safety processor 302 may communicate a heartbeat signal or a response to a query from the watchdog circuit 362 to indicate to the watchdog circuit 362 that the safety system 240 is operating properly. If the watchdog circuit 362 does not receive an expected signal from the safety processor 302, the watchdog circuit 362 disables the materials testing system 100 and notifies an operator.

[0074] The example safety processor 302, the example emergency stop 322, the example guard interlock 330, the example crosshead travel limit(s) 352, and / or the example watchdog circuit 362 are coupled (e.g., connected via hardware) to the actuator disable circuit 326. When any of the safety processor 302, the emergency stop 322, the guard interlock 330, the crosshead travel limit(s) 352, and / or the watchdog circuit 362 determine that a respective condition has been met to disable the materials testing system 100 (e.g., activation of the emergency stop switch 322, tripping of the guard 328, exceeding the crosshead travel limit 352, and / or triggering of the watchdog circuit 362), the actuator disable circuit 326 is used to activate the motor braking circuit 316 and the actuator disable circuit 308. The safety processor 302 can determine that the state of the materials testing system 100 is an invalid state.

[0075] Although the example control processor 238 and safety processor 302 are shown as separate processors, in other examples, the control processor 238 and safety processor 302 may be combined into a single processor or set of processors that are not divided into control and safety functions. Additionally, the control processor 238, safety processor 302, and / or combined processors may include non-processing circuitry, such as analog and / or digital circuitry that performs one or more dedicated functions.

[0076] Figures 4A and 4B show a flow chart depicting example machine-readable instructions 400 that may be executed by the safety processor 302 of Figure 3 to control a state of the materials testing system of Figures 1-3. The example instructions 400 may be executed to determine a state of the materials testing system from a plurality of predefined states, implement limits on actuators, and automatically set the state of the materials testing system to one of the limit states in response to completion of an operation involving control of the actuators.

[0077] In block 402, the materials testing system 100 and / or one or more subsystems may be powered on. If the materials testing system 100 has not been powered on, block 402 repeats until the materials testing system 100 is powered on. Once the materials testing system 100 is powered on (block 402), in block 404, the safety system 240 sets the state of the materials testing system 100 to a disabled state and disables one or more actuators (e.g., motor 242, grip actuator(s) 246). For example, the safety system 240 may default the actuator disable circuit 308 to de-energize the motor 242.

[0078] At block 406, the safety processor 302 is initialized. For example, the safety processor 302 may perform fault checks (e.g., checking inputs, outputs, and / or attached devices for open and / or closed circuits), redundancy checks (e.g., determining that redundant inputs and / or redundant outputs match), and / or other initialization processes.

[0079] At block 408, the safety processor 302 determines whether any faults are detected in the safety system 240 (e.g., detected during an initialization process). If a fault is detected (block 408), then at block 410, the safety processor 302 outputs a fault alert (e.g., via the control panel 250, the computing device 104, etc.). The example instructions 400 may then end.

[0080] If no fault is detected (block 408), then in block 411 the safety processor 302 determines whether an operator input has been received to transition the materials testing system 100 from the disabled state to the setup state. For example, the safety processor 302 may require one or more specified inputs (e.g., pressing an unlock button) to transition from the disabled state. If no operator input has been received (block 411), then block 411 repeats while the materials testing system 100 remains in the disabled mode, waiting for operator input.

[0081] Once operator input is received (block 411), the safety processor 302 sets the state of the materials testing system 100 to a setup state in block 412. In accordance with the setup state setting, the safety processor 302 enables the actuator(s) (e.g., motor 242), limits the actuator(s), and indicates the state (e.g., via status indicator 252) as the setup state. In some examples, the safety processor 302 controls one or more visual indicators on the control panel 250 to selectively highlight corresponding ones of the operator selectable inputs (e.g., mode switch 254) based on the state of the materials testing system 100 being the setup state. For example, the safety processor 302 can control the visual indicators to highlight inputs that the operator can use in the setup mode and to de-emphasize inputs that cannot be used in the setup mode.

[0082] In block 414, the safety processor 302 monitors the input signals (e.g., sensor signals 320, 332, 338, 346, 350), feedback signals (e.g., feedback signals 315, 340, 360), and / or control signals (e.g., signals from the control processor 238) of the safety system 240. The safety processor 302 may monitor such signals to identify, for example, operator commands and / or conditions that cause the safety processor 302 to recognize a change in the state of the materials testing system 100.

[0083] At block 416, the safety processor 302 and / or control processor 238 determine whether an operator control signal has been received to operate the actuator(s) with limits (e.g., at low speed or low pressure). For example, an operator may select one or more mode switches 254 to operate the crosshead 244 in a slow jog via the motor 242. If an operator control signal to operate the actuator has been received (block 416), then at block 418, the control processor 238 controls the actuator according to the limits applied by the safety processor 302 (e.g., speed limits, force limits, operator clearance limits).

[0084] At block 420, the safety processor 302 outputs an indication of the controlled operation. For example, the safety processor 302 may control one or more of the status indicators 252 to flash, cause the computing device 104 to output an indication of the operation, and / or provide any other indication(s).

[0085] In block 422, the safety processor 302 monitors the input signals (e.g., sensor signals 320, 332, 338, 346, 350), feedback signals (e.g., feedback signals 315, 340, 360), and / or control signals (e.g., signals from the control processor 238) of the safety system 240. In block 424, the safety processor 302 determines whether an actuation has ended. For example, the safety processor 302 may pulse the mode switch 254 to determine whether one or more of the operator control signals have changed, and / or may monitor the input and feedback signals to identify guard and / or interlock triggers, failures, and / or any other events that cause an interruption in actuation. If the actuation has not ended (block 418), control returns to block 418 to continue controlling the actuators.

[0086] Once the operation is completed (block 424 ), the safety processor 302 returns control to block 412 .

[0087] 4B, if an operator control signal has not been received to operate the actuator(s) with limits (block 416), then in block 426 the safety processor 302 and / or control processor 238 determine whether an operator control signal has been received to operate the actuator(s) with reduced limits (e.g., at a higher speed or pressure). For example, an operator input may be received to jog the crosshead 244 at a higher speed and / or to apply a higher clamping pressure to the test specimen via the pneumatic grips 248. Additionally or alternatively, an operator input and / or program input to perform a material test may involve setting the state of the materials testing system 100 as a caution state for a period of time prior to entering a test state and performing a test. If an operator control signal has not been received to operate the actuator(s) with reduced limits (block 426), then control returns to block 412.

[0088] If an operator control signal is received to operate the actuator(s) with reduced limits (block 426), then in block 428 the safety processor 302 sets the state of the materials testing system 100 to a caution state and reduces the actuator limit(s) (e.g., the limits on the grip actuator(s) 246). In some examples, the safety processor 302 may also allow the motor 242 and / or the grip actuator(s) 246 to be controlled by the control processor 238 in the caution state. The example safety processor 302 further controls the status indicator 252 to indicate that the materials testing system 100 is in the caution state.

[0089] At block 430, the safety processor 302 and / or the control processor 238 determine whether an operator control signal has been received to perform a material test (e.g., using reduced limits) and / or another action using reduced limits (e.g., a high speed jog of the crosshead 244). For example, an operator input and / or input from the computing device 104 may be received to perform a programmed material test involving high forces and / or high pressures.

[0090] If an operator control signal is received to perform a material test and / or another action (block 430), then the safety processor 302 sets the state of the materials testing system 100 to a test state and enables the actuator(s) (e.g., motor 242, grip actuator(s) 246) in block 432. The example safety processor 302 further controls the status indicator 252 to indicate that the materials testing system 100 is in the test state.

[0091] At block 434, the control processor 238 controls the actuators to perform the programmed test and / or another action (e.g., with the limit reduced and / or removed). At block 436, the safety processor 302 outputs an indication of the ongoing material test. For example, the safety processor 302 may control one or more of the status indicators 252 to flash, may cause the computing device 104 to output an indication of unrestricted operation, and / or may provide any other indication(s).

[0092] In block 438, the safety processor 302 monitors the input signals (e.g., sensor signals 320, 332, 338, 346, 350), feedback signals (e.g., feedback signals 315, 340, 360), and / or control signals (e.g., signals from the control processor 238) of the safety system 240. In block 440, the safety processor 302 determines whether the material testing and / or other operations are complete. For example, the safety processor 302 may pulse the mode switch 254 to determine whether one or more of the operator control signals have changed, and / or may monitor the input and feedback signals to identify any other events that cause guards and / or interlocks to trigger, fail, and / or cease operation. If the operations are complete (block 440), control returns to block 434 to continue performing the material testing and / or other operations.

[0093] Once the operation is completed (block 440 ), the safety processor 302 automatically changes state to a restricted state, such as a setup state, and returns control to block 412 .

[0094] Figure 5 illustrates an example operator interface 500 that can be used to implement the control panel 250 of Figures 2 and 3. The operator interface 500 can be attached to the example test instrument 102, located proximate to the test instrument, and / or located remotely from the test instrument 102. For example, the operator interface 500 can be implemented as a built-in operator panel or switches on the base of the test instrument 102.

[0095] The example operator interface 500 includes a number of input devices (e.g., buttons, switches, etc.) that provide input to the control processor 238 and / or safety system 240 of Figure 2 and / or Figure 3. The example input device includes a state control button 502 that may be required to be used to control transitions from restricted states (e.g., setup state) to non-restricted states (e.g., caution state, test state) and to perform operations involving the non-restricted state. The state control button 502 may be considered an "unlock" button or safety input device that allows use of the materials testing system in the non-restricted state.

[0096] The jog buttons 504, 506 control the motor 242 to jog the crosshead 244 up or down (or left and right, or any other orientation-based direction) (for directional crosshead movement) and / or in a right or left rotation direction (for rotational crosshead movement). When pressed individually, the jog buttons 504, 506 control the crosshead 244 to move up or down at a slower speed (e.g., as determined by the safety processor 302). When the jog buttons 504, 506 are pressed simultaneously with the state control button 502, the safety processor 302 can reduce the speed limit on the motor 242, allowing for faster jogging of the crosshead 244. The example jog buttons 504, 506 can function as directional input devices. In examples where the crosshead 244 provides a rotational force or movement, the directional input device can include a rotational input device, such as right and left rotation.

[0097] As used herein, received "simultaneously" refers to both inputs being activated or pressed at any given time, and not necessarily that both buttons must be initially pressed at the exact same moment.

[0098] A start button 508 controls the control processor 238 to begin a material test. A return button 510 controls the control processor 238 to return the crosshead 244 to a predetermined position, which can be done slowly or quickly. In some examples, the safety processor 302 requires that the start button 508 and / or return button 510 be pressed along with the state control button 502. A stop button 512 controls the control processor 238 to stop or pause a test in progress. An emergency stop switch 514 can be included to implement the emergency stop switch 322 of FIG. 3.

[0099] The operator interface 500 further includes status indicators 516-522 that output an indication of the current status of the materials testing system 100. The example status indicators 516-522 are lights that represent each of the conditions of the materials testing system 100 that the safety processor 302 can determine. In the example of Figure 5, the operator interface 500 includes an invalid status indicator 516, a setup status indicator 518, a caution status indicator 520, and a test status indicator 522. Each of the status indicators 516-522 is illuminated when the safety processor 302 determines that the materials testing system 100 is in the corresponding condition, and any status indicator 516-522 that does not correspond to the current condition is turned off.

[0100] FIG. 6 illustrates another example operator interface 600 that can be used to implement the control panel 250 of FIGS. 2 and 3. The example operator interface 600 can be a handset with a limited set of input devices (e.g., buttons, switches, etc.). The operator interface 600 can be attached to the example test apparatus 102, located proximate to the test apparatus, and / or located remotely from the test apparatus 102. The operator interface 600 includes a status control button 602 (e.g., similar to or identical to the status control button 502 of FIG. 5), jog buttons 604, 606 (e.g., similar to or identical to the jog buttons 504, 506), a start button 608 (e.g., similar to or identical to the start button 508), and a return button 610 (e.g., similar to or identical to the return button 510).

[0101] The operator interface 500, 600 may include custom buttons 612, or soft keys, that provide programmable functions to the operator. In some examples, the programmable functions are subject to one or more of the restricted states.

[0102] FIG. 7 illustrates the example material testing system 100 of FIG. 1 and the operator interface of FIGS. 5 and 6 during the startup routine of the material testing system 100. The material testing system 100 is powered on and initialized in a disabled state. In the disabled state, the disabled indicator 516 is illuminated (e.g., white) to indicate that the material testing system is in a disabled state. In addition, the user interface 700 executing on the computing device 104, 200 of FIGS. 1 and 2 also includes a prominent operation indicator 702 indicating that the material testing system 100 is in a disabled state. The example operator interfaces 500 and 600 only illuminate or highlight buttons that provide functionality when pressed. In the power-up stage (e.g., disabled state), only the state control button 602 is functional. In addition to power-up events, the disabled state can occur when an emergency stop switch is triggered, when a guard system is triggered, in response to a fault, and / or in response to any other event to which the safety processor 302 responds by setting the state to a disabled state.

[0103] When the operator presses the state control button 602, the safety processor 302 changes the system to the setup state. Figure 8 shows the example materials testing system 100 of Figure 1 in the setup state of the materials testing system 100, and the operator interfaces 500, 600 of Figures 5 and 6. After the safety processor 302 sets the state to the setup state, the safety processor 302 controls the setup indicator 518 to light (e.g., blue or green) to indicate the setup state to the operator. In addition, the user interface 700 includes a prominent indication 802 that the materials testing system 100 is in the setup state (e.g., ready for setup). In the setup state, additional control buttons are highlighted or lighted (e.g., jog) to indicate that additional functionality is now available.

[0104] 9 illustrates the example materials testing system 100 of FIG. 1 and the operator interfaces 500, 600 while jogging the crosshead 244 with limited actuation in a setup state. While the materials testing system 100 is in the setup state (e.g., as shown in FIG. 8), the operator can press either of the jog buttons 604, 606 on the operator interface 600 to instruct the control processor 238 to move the crosshead 244 to a desired position. When either of the jog buttons 604, 606 is pressed, the safety processor 302 limits the movement of the crosshead 244 (via the motor 242) to a limited jog speed. While jogging, the user interface 700 includes a prominent indicia 902 that indicates that the materials testing system 100 is performing a jog move. This can include text, flashing of the indicia 902 and / or the setup indicator 518, and / or any other highlighting.

[0105] FIG. 10 illustrates the example materials testing system 100 of FIG. 1 and the operator interface of FIGS. 5 and 6 while jogging the crosshead 244 with reduced constraints in the caution or test state. For example, in some applications, the crosshead 244 must be moved a relatively long distance, which may take a significant amount of time at a limited speed. To accommodate practical needs, reduce travel time, and eliminate incentives to circumvent the safety system 240, the safety processor 302 may reduce constraints in one or more non-restricted states to allow for high speed jogging of the crosshead 244. While the materials testing system 100 is in the setup state shown in FIG. 9, the operator may simultaneously press the state control button 602 and one of the jog buttons 604, 606. In response to the combination of buttons 602 and 604 or 606, the control processor 238 controls the motor 242 to move the crosshead 244, and the safety processor 302 sets the state of the materials testing system 100 to a test state (or a caution state) and reduces the restrictions applied to the motor 242. As a result, the motor 242 is allowed to move the crosshead faster in the commanded direction. The safety processor 302 further controls the test indicator 522 (or caution indicator 520) to light and / or flash, and the user interface software includes a prominent danger indicator 1002 to indicate that the materials testing system 100 is performing a jog move. This can include text, display 1002 and / or flashing of the test indicator 522 (or caution indicator 520), and / or any other highlighting. In some examples, the danger indicator 1002 can continuously display an active warning label that warns of a particular potential danger.

[0106] If the operator releases the state control button 602, the jog movement is allowed to continue with reduced limits in the test state. When the operator releases the jog buttons 604, 606, the control processor 238 stops the jog movement and the safety processor 302 automatically sets the state of the materials testing system 100 to the setup state and restores the limits. In some other examples, when the operator releases either the state control button 602 or the jog buttons 604, 606, the safety processor 302 automatically sets the state of the materials testing system 100 to the setup state and restores the corresponding limits.

[0107] FIG. 11 illustrates the example material testing system 100 of FIG. 1 and the operator interfaces 500, 600 while controlling the actuation of a pneumatic grip (e.g., pneumatic grip 248 of FIG. 2) with limited actuation in a setup state. As shown in FIG. 11, the material testing system 100 is in a setup state (similar to FIG. 8) as indicated by the illuminated setup indicator 518 and indicator 802 in the user interface 700. The example of FIG. 11 further includes an operator interface in the form of a foot pedal 1102 that can be used by an operator to control the grip actuator(s) 246 to close and / or open the pneumatic grip(s) 248. The operator inserts the specimen 1104 and presses the foot pedal 1102 to close the pneumatic grip 248. The example control processor 238 controls the grip actuator 246 to close the pneumatic grip 248 against the specimen 1104. In the setup state, the safety processor 302 controls the grip controller 354 to limit the air pressure that can be applied by the grip actuator(s) 246 and the gripping force that can be applied by the pneumatic grip(s) 248. While the state of the material processing system 100 remains in the setup state, the safety processor 302 monitors the applied pressure (e.g., via pressure sensor 358) to ensure that the air pressure does not exceed an upper limit.

[0108] FIG. 12 illustrates the example materials testing system 100 of FIG. 1 and the operator interface 500, 600 while controlling the actuation of the pneumatic grips 248 with reduced restrictions in a caution or test state. In the example of FIG. 12, the specimen 1104 is gripped in the pneumatic grips 248 and closed at a low pressure setting (as discussed with respect to FIG. 11). The operator can initiate the high pressure clamping process by pressing the state control button 602. The safety processor 302 determines that the state control button 602 has been pressed and, in response, reduces the restrictions on the grip actuator 246 to allow for increased grip pressure. The safety processor 302 also controls the caution indicator 520 (e.g., yellow) and the user interface 700 displays a prominent indicator 1202 indicating that the materials testing system 100 is in a caution state (or another non-restrictive state). This can include text, flashing of the display 1202 and / or the caution indicator 520, and / or any other highlighting. The safety processor 302 and / or the control processor 238 may highlight the start button 508, 608 and / or the return button 510, 610 to indicate that the buttons 508, 608, 510, 610 are available for use by an operator (e.g., perform a function when pressed).

[0109] After performing the high pressure clamp, the example safety processor 302 may set the state of the materials testing system 100 to a setup state and apply associated limits to the actuator(s) 242 , 246 .

[0110] 13A, 13B, and 13C show the example materials testing system 100 of FIG. 1 progressing from a setup state to a caution state and a test state to begin a materials test, and the operator interfaces 500, 600. The example setup state shown in FIG. 13A can be similar or identical to the setup state shown in FIG. 8, except that the specimen 1302 is gripped in the grips 248 and closed at the high pressure setting.

[0111] An operator can initiate a material test by first pressing the status control button 602 and then pressing the start button 608. In response to pressing the status control button 602, the safety processor 302 controls the caution indicator 520 to light (FIG. 13B) and the user interface 700 displays an indication 1304 of the caution status (e.g., a yellow border and / or an active warning overlay). In response to a subsequent press of the start button 608, the safety processor 302 then transitions to lighting the test indicator 522 (FIG. 13C) and the user interface 700 displays an indication 1306 of the test status (e.g., a red border and / or an active warning overlay). The control processor 238 can then proceed to execute the configured test once the safety processor 302 sets the state to a test state (e.g., unrestricted drive mode). The overlay in the user interface 700 can be removed after a period of time to allow the user to observe the ongoing test measurement on the user interface 700. Meanwhile, the safety processor 302 may continue to provide other visual, audible, and / or otherwise perceptible warnings during the test (e.g., displaying or flashing the test indicator 522, displaying or flashing a red border such as display 1306 on the user interface 700).

[0112] In some examples, the control processor 238 can be configured with a test method that pauses the test for operator interaction with the specimen 1302, such as removal of the extensometer. When the test reaches a point where interaction is required, the control processor 238 pauses the test (e.g., ceases actuation by the motor 242). Once the pause point is reached, the safety processor 302 places the materials testing system 100 in a setup state and the user interface 700 displays an indication that the test is paused. Additionally or alternatively, the safety processor 302 can control the setup indicator 518 to visually indicate (e.g., light up, flash) that the test is paused and not completed.

[0113] The operator can then resume the test by simultaneously pressing a state control button 602 (e.g., unlock) and the start button 608. The safety processor 302 and control processor 238 can then resume the test using the same sequence of indicators as initiating the test as described above. In some examples, when the state control button 602 is pressed, the user interface 700 displays an indication that the system is in a caution state and that the test is paused.

[0114] Once the test is complete, the safety processor 302 automatically sets the state to the setup state and applies the associated limits.

[0115] 14A, 14B, and 14C show the example materials testing system of FIG. 1 and the operator interfaces 500, 600 of FIGS. 5 and 6 while progressing from the SETUP state to the CAUTION state and TEST state to return the crosshead 244 to the desired position. After the previous test is completed, the materials testing system 100 is set to the SETUP state, indicated by the illumination of the SETUP indicator 518. The crosshead 244 may be positioned, for example, at the location where the previous test was completed. In the SETUP state, the operator may remove the specimen and / or interact with the tester 102 and / or the operator interfaces 500, 600, with restrictions applied by the safety processor 302.

[0116] When the operator is ready to return the crosshead 244 to the desired position (e.g., to perform another test), the operator can initiate return by simultaneously or sequentially pressing the status control button 602 and the return button 610. In response to pressing the status control button 602, the safety processor 302 controls the caution indicator 520 to illuminate (FIG. 14B) and the user interface 700 displays a caution status indication 1402 (e.g., a yellow border and / or an active warning overlay). In response to a subsequent press of the return button 610, the safety processor 302 then transitions to lighting the test indicator 522 (FIG. 14C) and the user interface 700 displays a test status indication 1404 (e.g., a red border and / or an active warning overlay). The control processor 238 can then proceed to control the motor 242 to move the crosshead 244 with a reduced or removed speed limit when the safety processor 302 sets the state to a test state (e.g., unlimited drive mode).

[0117] After the crosshead 244 reaches a desired position (eg, a test start position), the safety processor 302 automatically sets the state to the setup state.

[0118] The materials testing system 100 has the safety features enabled and operational consistently (e.g., constantly), but some of the parameters used by the safety system 240 may be adjustable to provide a desired interaction (e.g., slower jog speeds than the default jog speeds). The example computing device 104 may allow an administrator or other authorized operator to control some parameters of the safety system 240.

[0119] Although the computing system 104 may provide an interface for configuration of the safety system parameters, the example computing system 104 does not participate in the implementation of the parameters. To change the parameters of the safety system 240 from the default parameters, an authorized operator or administrator may be required to enable a software security system that authenticates the authorized operator making the changes.

[0120] When the security system is enabled, the operator may change parameters such as jog rate, grip pressure, control points (e.g., local or remote), interlock behavior (movable guards), and / or whether to dismiss notifications when performing an action such as starting a materials test. Before and / or after a change, the security system requires entry of valid credentials that allow the change in settings to be committed to the safety system 240 for implementation. The safety system 240 may be shut down to store the configuration change, which will result in the state of the materials testing system 100 changing to a disabled state.

[0121] A changeable security system is a keyless system that allows an administrator or other authorized operator to configure the security system in a manner consistent with a particular risk assessment, while preventing a standard operator from overriding those settings. The keyless management feature prevents accidental and / or intentional misuse that can occur with traditional security systems that use keys or selection controls.

[0122] 3, in some examples, grip actuator(s) 246 are implemented using a manifold and a number of fill and / or exhaust valves and / or pressure sensors and / or pressure switches that control the application and / or release of pneumatic pressure to pneumatic grip(s) 248. An example manifold, example fill and exhaust valves, and example pressure switches that can be used to implement grip actuator(s) 246 are disclosed in U.S. Patent Application Publication No. 2019 / 0113427, filed March 31, 2017, the entirety of which is incorporated herein by reference.

[0123] The example manifold and multiple fill and / or exhaust valves and / or pressure sensors and / or pressure switches can be coupled to a safety processor 302 that controls high and / or low pressure states of the pneumatic grip(s) based on the conditions described above.

[0124] Figure 15 is a block diagram of an example pneumatic grip system 1500 that can be used to implement a portion of the safety system of Figure 3. The example pneumatic grip system 1500 includes a safety processor 302 that receives inputs from a main pressure sensor 1502, a pressure sensor 1504 in an upper pneumatic grip 1508, and a pressure sensor 1506 in a lower pneumatic grip 1510.

[0125] The safety processor 302 also controls the fill valve 1512 to selectively allow the application of air pressure into a manifold 1514 that can direct air to the upper grip or the lower grip. The safety processor 302 controls the dump valve 1516 to depressurize the system. The safety processor 302 also controls the upper grip valve 1518 to direct air pressure to the upper grip 1508 and / or release pressure from the upper grip 1508 via an exhaust 1520, and the lower grip valve 1522 to direct air pressure to the lower grip 1510 and / or release pressure from the lower grip 1510 via an exhaust 1520. The dump valve 1516, the upper grip valve 1518, and the exhaust 1520 of the lower grip valve 1520 may be a combined exhaust channel or separate exhaust channels.

[0126] The grip fill control valves 1512, 1516, 1518, 1522 may be controlled by the safety processor 302 and / or another processor, either of which may perform the task or subroutine of controlling the grip pressure. An exemplary valve that may be used for the fill valves and / or exhaust valves is a solenoid valve, such as a proportional valve. In operation, the safety processor 302 controls the fill valves 1512, 1518, 1522 and the exhaust valve 1516. When the fill solenoid of the fill valve 1512 is de-energized (e.g., FALSE command value), the air supply entering the room is cut off. When the fill solenoid of the fill valve 1512 is energized (e.g., TRUE command value), the air supply is routed to the main internal manifold piping. When the discharge solenoid of the discharge valve 1516 is de-energized (e.g., FALSE command value), the main internal manifold piping is connected to the external exhaust port. When the dump solenoids of the dump valves 1516 are energized (e.g., TRUE command value), they isolate the main internal manifold plumbing from the exhaust port. These solenoids have four possible states. Fill command = false, release command = false: Release pressure (default state) Fill command = false, discharge command = true: Maintain pressure Fill Command = True, Drain Command = False: Not used. This state should be avoided as it exhausts the input air supply directly out the exhaust port. Fill command = true, discharge command = true: Pressure fill

[0127] The three operating states that can be controlled by the safety processor 302 are fill, bleed, and hold. By controlling the system to the fill state, the internal pressure increases according to the amount of time in the fill state. By controlling the system to the bleed state, the internal pressure decreases according to the amount of time in the bleed state. By controlling the system to the hold state, the current internal pressure is maintained at or further settling minus a small air leak, if any.

[0128] Because electromechanical solenoids do not change states instantaneously, the safety processor 302 can use the transition times to coordinate the timing of transitions between the fill, discharge, and hold states.

[0129] The pressure sensors 1502, 1504, 1506 may be implemented using an analog-to-digital converter that receives analog air pressure samples from the pressure sensors and converts the analog samples to digital sample values.

[0130] One drawback of conventional pneumatic grip systems is that the pressure sensor is located in the manifold and not in the body of the grip, and conventional control systems do not account for the delay between when the air pressure enters the manifold and when the air pressure reaches the pneumatic grip. As shown in FIG. 16A, a conventional pneumatic grip control system is commanded to a first pressure. The pressure sensor located in the manifold reads the increased pressure almost instantly. However, there is a hose connecting the manifold to the body of the grip, which creates a significant delay in pressurizing the grip. For example, there may be a delay of hundreds of milliseconds to several seconds for the grip to reach the same pressure as the manifold. As a result, the true pressure at the grip during pressurization is not known.

[0131] The disclosed example overcomes the delay in pressure information by applying air pressure at timed intervals. For example, the safety processor 302 can control the fill valve 1512, the upper grip valve 1518, and / or the lower grip valve 1522 by energizing the grip solenoids several times to pass short bursts or pulses of air into the grips, then holding to allow the system to stabilize. FIG. 16B shows an example graph showing the bursts of air used to increase grip pressure. The safety processor 302 monitors the rate of change (e.g., slope) of pressure as it drops during the hold. When the slope of the line stabilizes (e.g., when the slope is sufficiently flat or below a threshold), the true pressure reading of the body of the grip 1508, 1510 has been reached.

[0132] Because the main pressure sensor 1502 is located very close to the full pressure air inlet, the pressure measured by the main pressure sensor 1502 will rise quickly to near the external pressure as long as the fill valves 1512, 1518, 1522 are in the fill state. The sensors 1504, 1506 will not accurately reflect the pressure in the grips 1508, 1510 unless the valves 1512, 1518, 1522 are switched to a hold state for a period of time to allow the pressure in the system to stabilize. The hold time has been found to vary widely. Most of the variation is dependent on the particular grip being used due to differences in the volume of air required in the air chambers of different size grips. Another source of variation is related to the amount of time air is allowed to flow into the grip. This overall settling time has been experimentally determined to be greater than 50 ms for the smallest grips and less than 600 ms for the largest grips. Using a fixed time of 600 ms would unnecessarily slow down the operation of smaller grips. By monitoring the rate of change of pressure during the hold (see, e.g., FIG. 16B), the safety processor 302 can detect stabilization of the air pressure. For example, as the pressure approaches stabilization, the rate of change (or slope) approaches zero. When the rate of change falls below a predetermined threshold, the hold is terminated.

[0133] The example safety processor 302 can adjust the delay of each wait period (e.g., settling time after an air pressure burst) based on the time it takes for the air pressure to stabilize. For example, the safety processor 302 can implement proportional and / or integral control with a gain based on the difference between the current pressure and the target pressure and / or based on the total time the system was different from the desired set point. By adjusting the wait time, the safety processor 302 can avoid having a fixed long delay that would significantly increase the time to reach the desired pressure.

[0134] At the end of the wait period, if the grip pressure is below the desired pressure, the safety processor 302 can repeat the burst of air pressure. Conversely, if the grip pressure is within a predetermined tolerance, the safety processor 302 can control the valve to maintain the air pressure. The example control processor 302 can use the state of the grip pressure to take action based on the grip pressure and / or other system states as described above. For example, when the grips are closed at a lower pressure, the safety processor 302 can allow the grip pressure to be increased to a higher pressure and / or allow the initiation of a test based on a limited or unlimited state.

[0135] The example control processor 302 can reduce the pressurization of the grips in a manner similar to increasing the pressure, such as by reducing the pressure in a burst. For example, if too much air is being admitted into the system and / or if the set point pressure is being reduced, the control processor 302 can control (e.g., energize, de-energize) the release valve(s) to vent a burst of air pressure from the grips and then go into a hold state to stabilize the pressure. If the measured pressure of the system is still above the desired set point, the control processor 302 can cause another burst of air to vent from the system until the desired set point pressure is reached.

[0136] In some examples, the safety processor 302 dynamically adjusts the gain based on the expected pressure increase in the last fill cycle (e.g., air pressure burst) and the actual pressure increase in the last fill cycle. If the actual pressure increase was less than the expected pressure increase, the safety processor 302 increases the gain. Conversely, if the actual pressure increase was greater than the expected pressure increase, the safety processor 302 decreases the gain. As a result, the safety processor 302 can be used simultaneously with grips of various sizes, such as grips having grip pressures from 50 Newtons (N) to 10,000 N, without the user providing information on grip size. A 50 N grip has a small volume and fills effectively using a small air pressure burst. On the other hand, a 10,000 N grip has a large volume and would take a much longer time to fill using an air pressure burst of the same duration used for a 50 N grip. Thus, the safety processor 302 determines (e.g., learns) that size volume is related to it and adjusts the air pressure filling parameters.

[0137] The method and system can be implemented in hardware, software, and / or a combination of hardware and software. The method and / or system can be implemented in a centralized manner in at least one computing system, or in a distributed manner where different elements are distributed across several interconnected computing systems. Any kind of computing system or other device adapted to perform the methods described herein is suitable. A typical combination of hardware and software can include a general-purpose computing system, with a program or other code that, when loaded and executed, controls the computing system to perform the methods described herein. Another typical embodiment can include an application specific integrated circuit or chip. Some embodiments can include a non-transitory machine-readable (e.g., computer-readable) medium (e.g., flash drive, optical disk, magnetic storage disk, etc.), which stores one or more lines of code executable by a machine, thereby causing the machine to perform a process as described herein. As used herein, the term "non-transitory machine-readable medium" is defined to include all types of machine-readable storage media and to exclude propagating signals.

[0138] As used herein, the terms "circuit" and "circuitry" refer to physical electronic components (i.e., hardware) and any software and / or firmware ("code") that may comprise, be executed by, and / or otherwise be associated with hardware. As used herein, for example, a particular processor and memory may include a first "circuit" when executing a first one or more lines of code, and may include a second "circuit" when executing a second one or more lines of code. As used herein, "and / or" refers to any one or more of the items in a list linked by "and / or". As an example, "x and / or y" refers to any element of the triplet {(x),(y),(x,y)}. In other words, "x and / or y" means "one or both of x and y". As another example, "x, y, and / or z" means any element of the seven-element set {(x),(y),(z),(x,y),(x,z),(y,z),(x,y,z)}. In other words, "x, y, and / or z" means "one or more of x, y, and z." As used herein, the term "exemplary" means serving as a non-limiting example, instance, or illustration. As used herein, the term "for example" begins a list of one or more non-limiting examples, instances, or illustrations. As used herein, whenever circuitry includes the necessary hardware and code (if either is necessary) to perform a function, the circuitry is "operable" to perform that function, regardless of whether implementation of that function is disabled or enabled (e.g., by a user-configurable setting, factory trim, etc.).

[0139] Although the method and / or system have been described with reference to certain specific embodiments, those skilled in the art will recognize that various modifications and equivalents may be substituted without departing from the scope of the method and / or system. For example, blocks and / or components of the disclosed examples may be combined, divided, rearranged, and / or otherwise modified. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the disclosure without departing from the scope of the disclosure. Thus, the method and / or system is not limited to the particular embodiments disclosed. Instead, the method and / or system includes all embodiments falling within the scope of the appended claims, both literally and under the doctrine of equivalents. The inventions disclosed herein include the following: [Aspect 1] a pneumatic grip configured to grip a specimen under test based on an applied pressure; 1. A processor comprising: controlling a fill valve to increase the delivered pressure; stabilizing the delivered pressure after each increment; and adjusting a time of said pressurization based on comparing an expected pressure increase to an actual pressure increase during pressurization; a processor configured to control the pressure supplied to the pneumatic grip by repeating A materials testing system comprising: [Aspect 2] The materials testing system of aspect 1, wherein the pneumatic grip comprises a first grip and a second grip, and the processor is configured to control the pressure supplied to the pneumatic grip by controlling the pressure to at least one of the first grip or the second grip. [Aspect 3] 3. The materials testing system of claim 2, further comprising a second filling valve, the filling valve configured to control gas flow from a gas supply to the second filling valve, and the second filling valve configured to control gas flow from the filling valve to the first grip. [Aspect 4] 4. The materials testing system of claim 3, wherein the processor is configured to control the second fill valve to selectively increase pressure, maintain pressure, or release pressure via an exhaust. [Aspect 5] 4. The materials testing system of embodiment 3, further comprising a third fill valve configured to control gas flow from the fill valve to the second grip. [Aspect 6] 4. The materials testing system of claim 3, wherein the processor is configured to stabilize the delivered pressure after each increase by closing the fill valve and the second fill valve. [Aspect 7] 2. The materials testing system of embodiment 1, further comprising a release valve configured to vent pressure from the pneumatic grip. [Aspect 8] 8. The materials testing system of claim 7, wherein the fill valve comprises a first solenoid and the release valve comprises a second solenoid, and the processor is configured to control the first solenoid and the second solenoid to have a default state configured to release pressure from the pneumatic grip. [Aspect 9] 2. The materials testing system of claim 1, wherein the processor is configured to determine that the delivered pressure has stabilized based on a rate of change of the pressure. [Aspect 10] 10. The materials testing system of claim 9, wherein the processor is configured to determine that the delivered pressure has stabilized when the rate of change of the pressure is less than a threshold rate. [Aspect 11] The pressure supplied to the pneumatic device of the material testing system is controlling a fill valve to increase the delivered pressure; stabilizing the delivered pressure after each increase; and adjusting a time of said pressurization based on comparing an expected pressure increase to an actual pressure increase during pressurization; and controlling using a processor by repeating via said processor 16. A method for controlling a pneumatic device in a materials testing system, comprising: [Aspect 12] The method of claim 11, wherein the pneumatic grip comprises a first grip and a second grip, and controlling the pressure supplied to the pneumatic grip includes controlling the pressure to at least one of the first grip or the second grip. [Aspect 13] The controlling of the fill valve to increase the delivered pressure comprises: Controlling a gas flow from a gas supply to a second fill valve; controlling the second fill valve to control gas flow from the fill valve to the first grip; 13. The method of embodiment 12, comprising: [Aspect 14] 14. The method of embodiment 13, further comprising controlling the second fill valve to selectively increase pressure, maintain pressure, or release pressure via a vent. [Aspect 15] The method of claim 13, wherein controlling the fill valve to increase the supplied pressure includes controlling gas flow from the fill valve to the second grip by controlling a third fill valve. [Aspect 16] 14. The method of claim 13, wherein the stabilizing the delivered pressure comprises closing the fill valve and the second fill valve. [Aspect 17] 12. The method of embodiment 11, further comprising controlling a release valve to vent pressure from the pneumatic grip. [Aspect 18] The method of claim 17, wherein the fill valve comprises a first solenoid and the release valve comprises a second solenoid, the method further including controlling the first solenoid and the second solenoid to have a default state configured to release pressure from the pneumatic grip. [Aspect 19] 12. The method of embodiment 11, further comprising determining that the delivered pressure has stabilized based on a rate of change of the pressure. [Aspect 20] 20. The method of claim 19, wherein determining that the delivered pressure has stabilized is made in response to determining that the rate of change of the pressure is less than a threshold rate.

Claims

1. a pneumatic grip configured to grip a specimen under test based on an applied pressure; 1. A processor comprising: in response to determining that the current pressure is less than a target pressure for pressurization of the pneumatic grip, performing one of a plurality of fill cycles by controlling a fill valve to increase the delivered pressure; stabilizing the delivered pressure after the fill cycle by switching the fill valve to a hold state during a wait time; adjusting the wait time based on comparing an expected pressure increase to an actual pressure increase of a previous fill cycle of the plurality of fill cycles; a processor configured to control the pressure delivered to the pneumatic grip during the pressurization over the plurality of fill cycles by repeating A materials testing system comprising:

2. 2. The materials testing system of claim 1, wherein the pneumatic grips comprise a first grip and a second grip, and the processor is configured to control the pressure supplied to the pneumatic grips by controlling the pressure to at least one of the first grip or the second grip.

3. 3. The materials testing system of claim 2, further comprising a second fill valve, the fill valve configured to control gas flow from a gas supply to the second fill valve, and the second fill valve configured to control gas flow from the fill valve to the first grip.

4. The materials testing system of claim 3 , wherein the processor is configured to control the second fill valve to selectively increase pressure, maintain pressure, or release pressure via an exhaust.

5. The materials testing system of claim 3 , further comprising a third fill valve configured to control gas flow from the fill valve to the second grip.

6. The materials testing system of claim 3 , wherein the processor is configured to stabilize the delivered pressure after each increase by closing the fill valve and the second fill valve.

7. 10. The materials testing system of claim 1, further comprising a release valve configured to vent pressure from the pneumatic grip.

8. 8. The materials testing system of claim 7, wherein the fill valve comprises a first solenoid and the release valve comprises a second solenoid, and the processor is configured to control the first solenoid and the second solenoid to have a default state configured to release pressure from the pneumatic grip.

9. The materials testing system of claim 1 , wherein the processor is configured to determine when the delivered pressure has stabilized during the fill cycle based on a rate of change of the pressure.

10. 10. The materials testing system of claim 9, wherein the processor is configured to determine that the delivered pressure has stabilized during the fill cycle when the rate of change of the pressure is less than a threshold rate.

11. A material testing system comprising a pneumatic grip configured to grip a test specimen based on a pressure supplied thereto, the pneumatic grip comprising: in response to determining that the current pressure is less than a target pressure for pressurization of the pneumatic grip, performing one of a plurality of fill cycles by controlling a fill valve to increase the delivered pressure; stabilizing the delivered pressure after the fill cycle by switching the fill valve to a hold state during a wait time; adjusting the wait time based on comparing an expected pressure increase to an actual pressure increase of a previous fill cycle of the plurality of fill cycles; and controlling using a processor by repeating via said processor 23. The method of claim 22, wherein the pressure sensor detects a pressure change in a material testing system during the pressurization over the plurality of fill cycles.

12. 12. The method of claim 11, wherein the pneumatic grip comprises a first grip and a second grip, and wherein the controlling the pressure supplied to the pneumatic grip includes controlling the pressure to at least one of the first grip or the second grip.

13. The controlling of the fill valve to increase the delivered pressure comprises: Controlling gas flow from a gas supply to a second fill valve; controlling the second fill valve to control gas flow from the fill valve to the first grip; The method of claim 12, comprising:

14. 14. The method of claim 13, further comprising controlling the second fill valve to selectively increase pressure, maintain pressure, or release pressure via a vent.

15. 14. The method of claim 13, wherein the controlling the fill valve to increase the delivered pressure comprises controlling a third fill valve to control gas flow from the fill valve to the second grip.

16. 14. The method of claim 13, wherein the stabilizing the delivered pressure comprises closing the fill valve and the second fill valve.

17. The method of claim 11 , further comprising controlling a release valve to vent pressure from the pneumatic grip.

18. 18. The method of claim 17, wherein the fill valve comprises a first solenoid and the release valve comprises a second solenoid, the method further comprising controlling the first solenoid and the second solenoid to have a default state configured to release pressure from the pneumatic grip.

19. The method of claim 11 , further comprising determining that the delivered pressure has stabilized during the fill cycle based on a rate of change of the pressure.

20. 20. The method of claim 19, wherein the determining that the delivered pressure has stabilized during the fill cycle is made in response to determining that the rate of change of the pressure is less than a threshold rate.

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