Patent Description:
Reliability testing for an assembly, or moving components of an assembly, may involve repetitively performing intended and/or unintended movements of the components to verify that the components and/or assembly reliably operates for a defined minimum number of cycles of the movements. For example, reliability testing of a flexible substrate may involve repeatedly flexing the substrate in one or more ways, while testing for continued operation of the device and/or monitoring various modes of failure. Related prior art comprises <CIT>, <CIT>, <CIT>, <CIT>, <CIT> and <CIT>.

Methods and apparatus to perform load measurements on flexible substrates are disclosed, substantially as illustrated by and described in connection with at least one of the figures, as set forth more completely in the claims.

Conventional flexible substrate testing systems do not measure loads or stresses on the flexible substrates during folding or unfolding. Instead, conventional flexible substrate testing systems may involve testing such as defect analysis and other static testing and analysis.

Disclosed example flexible substrate testing systems and methods provide stress testing for flexible substrates, including measurement of dynamic and/or static loads on the flexible substrate during deformation such as folding and/or unfolding. Some disclosed example systems and methods reduce or minimize additional stress induced on the flexible substrate by the flexible substrate testing system itself. For example, some disclosed flexible substrate testing systems include fixturing that provides repetitive folding and unfolding of a flexible substrate, such as a flexible display screen. Disclosed examples configure the fixturing, such as guiding of the moving parts, such that the fixturing does not create additional compression or tension on the flexible substrate as the ends of the substrate are folded together or unfolded.

In contrast with conventional flexible substrate testing systems that perform two <NUM> degree bends, disclosed example test systems reduce or prevent stress induced on the substrate under test from the test fixture (e.g., stress other than the stress naturally and necessarily experienced by the material due to folding). Some conventional testing systems that perform two <NUM> degree bends attempt to eliminate such stress by holding the material such that section of the substrate is used to function as a buffer against tension and compression of the material.

In contrast with conventional test systems, disclosed example test systems are geometrically configured to rotate the portions of the substrate such that the substrate may fully extend in the open or unfolded position, but do not experience tension stress caused by rotation of the test fixture. As a result, disclosed example test systems and test fixtures for flexible substrates provide more accurate measurements of stress on flexible substrates during repetitive stress measurements.

Disclosed example flexible substrate testing systems include a first substrate support structure configured to hold a first portion of a flexible substrate under test, a second substrate support structure configured to hold a second portion of the flexible substrate, one or more actuators configured to move the first and second substrate support structures at respective angles to fold the flexible substrate, and load cells configured to measure loads on the first substrate support structure and the second substrate support structure while the actuator moves the first substrate support structure and the second substrate support structure.

In some example flexible substrate testing systems, the first and second substrate support structures are configured to fold the substrate to an angle of more than <NUM> degrees and less than or equal to <NUM> degrees. In some example flexible substrate testing systems, the first substrate support structure is configured to rotate up to <NUM> degrees and the second substrate support structure is configured to rotate up to <NUM> degrees to fold the substrate at an angle of up to <NUM> degrees. In some example flexible substrate testing systems, the one or more actuators are configured to move the first and second substrate support structures simultaneously.

In some example flexible substrate testing systems, the one or more actuators are configured to move the first and second substrate support structures by driving a single input shaft. In some example flexible substrate testing systems, the input shaft is coupled to a first secondary shaft configured to move the first substrate support structure and to a second secondary shaft configured to move the second substrate support structure. In some example flexible substrate testing systems, the first secondary shaft is coupled to the first substrate support structure via a first gearing system configured to rotate the first substrate support structure about a first axis defined by the first gearing system, and the second secondary shaft is coupled to the second substrate support structure via a second gearing system configured to rotate the second substrate support structure about a second axis defined by the second gearing system. In some example flexible substrate testing systems, the first and second gearing systems are configured to rotate the first portion of the flexible substrate and the second portion of the flexible substrate simultaneously and proportionally. In some example flexible substrate testing systems, the first axis and the second axis are spaced apart so as to create multiple folds in the substrate.

Some example flexible substrate testing systems include control circuitry configured to determine the loads on the flexible substrate based on load information from the load cells.

In some example flexible substrate testing systems, the first substrate support structure includes a first plate having a first surface and the second substrate support structure includes a second plate having a second surface. In some example flexible substrate testing systems, the flexible substrate testing system is configured to position a first plane of the first surface and a second plane of the second surface vertically during the folding and unfolding.

Some example flexible substrate testing systems include a first translation linkage configured to hold the first substrate support structure and to limit motion of the first substrate support structure in directions parallel to the first surface of the first substrate support structure. Some example flexible substrate testing systems include a second translation linkage configured to hold the second substrate support structure and to limit motion of the second substrate support structure in directions parallel to the second surface of the second substrate support structure. In some example flexible substrate testing systems, the first translation linkage includes a first four-bar linkage coupled to the first substrate support structure and the second translation linkage includes a second four-bar linkage coupled to the second substrate support structure.

Some example flexible substrate testing systems include control circuitry configured to determine the loads on the flexible substrate based on a dynamic load measured by the load cells during the folding or unfolding of the flexible substrate. Some example flexible substrate testing systems include control circuitry configured to determine the load on the flexible substrate based on a static load measured by the load cells at a completion of the folding or unfolding of the flexible substrate.

Disclosed example methods to measure loads on a flexible substrate involve: moving, via an actuator, a first portion of a flexible substrate under test and a second portion of the flexible substrate to fold or unfold the flexible substrate; and measuring a load on the flexible substrate resulting from the moving.

In some example methods, moving the first portion of the flexible substrate involves rotating a first substrate support structure holding the first portion of the flexible substrate, and moving the second portion of the flexible substrate involves rotating a second substrate support structure holding the second portion of the flexible substrate.

Some other disclosed example flexible substrate testing systems include: a first plate comprising a first surface configured to hold a first side of a flexible substrate under test; a first translation linkage configured to hold the first plate and to limit motion of the second plate in directions parallel to the first surface of the first plate; a second plate comprising a second surface configured to hold a second side of the flexible substrate; a second translation linkage configured to hold the second plate and to limit motion of the second plate in directions parallel to the second surface of the second plate; one or more actuators configured to move the first and second plates at respective angles to fold the substrate to an angle greater than <NUM> degrees and less than or equal to <NUM> degrees; and load cells configured to measure loads on the first plate and the second plate while the actuator moves the first plate and the second plate.

<FIG> are block diagrams illustrating an example flexible substrate test system <NUM> to perform mechanical property testing on a flexible substrate <NUM>. <FIG> illustrates the flexible substrate test system <NUM> in an open, flat, or unfolded position. <FIG> illustrates the test system <NUM> in a closed or folded position. The example flexible substrate <NUM> may be a flexible display screen or other device, fabric, material, and/or any other substrate. The system <NUM> of <FIG> is configured to repeatedly fold and unfold the flexible substrate <NUM> to measure stress (e.g., folding force) on the substrate <NUM>.

The example system <NUM> includes a first plate <NUM>, a second plate <NUM>, an actuator <NUM>, first and second load cells 112a, 112b, and first and second translation linkages 114a, 114b. The system <NUM> may include additional features, such as structural support or framing, processing circuitry, communications and/or input/output (I/O) circuitry, and/or any other components. The load cells 112a, 112b may output load measurements during folding and/or unfolding (e.g., measurements of dynamic load) and/or at the conclusion of a folding and/or unfolding process (e.g., measurements of static load).

When folded, the flexible substrate <NUM> is considered to have a first side <NUM> and a second side <NUM> on opposing ends of the bend <NUM> or fold in the substrate <NUM>. The first side <NUM> and the second side <NUM>. <FIG> illustrates the substrate in an unfolded or flat position (solid line) and folded position (dotted line).

The first plate <NUM> is a first substrate support structure, and has a first surface <NUM> to which the first side <NUM> of the substrate <NUM> is attached or affixed, and held stationary with respect to the first surface <NUM>. The second plate <NUM> is a second substrate support structure, and has a second surface <NUM> to which the second side <NUM> of the substrate <NUM> is attached or affixed, and held stationary with respect to the second surface <NUM>. The plates <NUM>, <NUM> are separated by a gap, which is bridged by a portion of the substrate <NUM> that forms the curve <NUM> when the substrate <NUM> is folded.

While the first and second substrate support structures in <FIG> are first and second plates, in other examples the first and second substrate support structures may be different. For example, other first and second substrate support structures may include clips or clamps to hold portions of the substrate <NUM> to enable folding without attachment of the substrate <NUM> to the plate.

The actuator <NUM> is coupled to the first plate <NUM> and the second plate <NUM> to move the plates <NUM>, <NUM>. As illustrated in <FIG>, the actuator <NUM> moves plates <NUM>, <NUM> between an open, flat, or unfolded position, in which the substrate <NUM> is unfolded (<FIG>) and a closed, or folded, position in which the substrate <NUM> is folded <FIG>). In some examples, the actuator <NUM> may be a motor attached to the first and second plates <NUM>, <NUM> via respective linkages.

The load cells 112a, 112b measure loads on the first plate <NUM> and the second plate <NUM>, respectively, while the actuator <NUM> moves the plates <NUM>, <NUM>. In particular, the load cells 112a, 112b measure stress on the substrate <NUM> as the substrate <NUM> is folded by measuring load exerted by the first side <NUM> of the substrate <NUM> onto the first plate <NUM> and load exerted by the second side <NUM> of the substrate <NUM> onto the second plate <NUM>.

The translation linkages 114a, 114b limit movement of the first plate <NUM> and the second plate <NUM> in directions other than the directions in which the load cells 112a, 112b are loaded by the first plate <NUM> and the second plate <NUM>, respectively. For example, if the load cell 112a is configured to measure loads in a direction perpendicular to the plane of the first surface <NUM>, the translation linkage 114a limits movement of the first plate <NUM> in directions parallel to the plane of the first surface <NUM> while permitting load to be transferred from the first plate <NUM> to the load cell 112a (e.g., in a direction perpendicular to a surface of the first plate <NUM> and/or the substrate <NUM>). Similarly, if the load cell 112b is configured to measure loads in a direction perpendicular to the plane of the second surface <NUM>, the translation linkage 114b limits movement of the second plate <NUM> in directions parallel to the plane of the second surface <NUM> while permitting load to be transferred from the second plate <NUM> to the load cell 112b (e.g., in a direction perpendicular to a surface of the second plate <NUM> and/or the substrate <NUM>).

The example translation linkages 114a, 114b may each include one or more four-bar linkages coupled to frames that are fixed with respect to the load cells 112a, 112b. In some examples, the translation linkages 114a, 114b are further limited in a direction toward the load cell 112a, 112b to prevent overloading of the load cells 112a, 112b. For example, a stopping point may be attached to the frame to prevent movement of the four-bar linkage(s) and the first plate <NUM> toward the load cell 112a beyond the stopping points.

In operation, the example load cells 112a, 112b may be biased or offset, after securing the substrate <NUM> to the first plate <NUM> and the second plate <NUM>, to subtract a preload from the test measurements. For example, the preload on the load cells 112a, 112b may occur due to the weight of the plates <NUM>, <NUM>, the weight of translation linkages 114a, 114b, and the weight of the first side <NUM> of the substrate <NUM> on the first plate <NUM> and the weight of the second side of the substrate <NUM> on the second plate <NUM>. By determining the preloads on the load cells 112a, 112b, the load cells 112a, 112b can be calibrated or offset to measure the stress on the substrate <NUM> during folding and unfolding.

In some examples, the test system <NUM> is positioned such that the first plate <NUM> and the second plate <NUM> are positioned vertically, and the plates <NUM>, <NUM> are moved horizontally. For example, the axis of rotation of the plates <NUM>, <NUM> is vertical, or straight up and down, and the weights of the plates <NUM>, <NUM> are not directed toward the load cells 112a, 112b.

To reduce or prevent inducing stress on the substrate <NUM> due to the fixturing, the axes of rotation 126a, 126b (e.g., pivot points) are offset from the substrate <NUM>. The length of the offset may be based on, for example, a folding radius r of the substrate <NUM>. When the substrate <NUM> is unfolded into the open position, the distance between the plates <NUM>, <NUM> (e.g., a distance bridged by the substrate <NUM>) may also be based on the radius, such as a distance of approximately <NUM>*r, which is approximately equal to the circumference of the folded portion of the substrate <NUM> in the folded or closed position. Additionally or alternatively, the offset between the axes 126a, 126b and the plates <NUM>, <NUM> may be configured based on the radius, such that the distance between the plates <NUM>, <NUM> is approximately <NUM>*r. By configuring the axes 126a, 126b, and/or configuring the plates <NUM>, <NUM> based on stationary axes 126a, 126b and the desired fold radius, the test system <NUM> permits the substrate <NUM> to fully extend when unfolded and to be folded to a desired fold radius, without inducing tension or compression stress on the substrate <NUM> due to the folding. In some examples, the folding radius may cause the substrate <NUM> to fail prematurely, which can be measured as part of the testing.

In the example of <FIG>, the measurements output by the load cells 112a, 112b are compensated for the weights of the first plate <NUM> and the second plate <NUM> and/or the inertial load of the first plate <NUM> and/or the inertial load of the second plate <NUM>, to provide a measurement of the forces, stresses, or loads on the flexible substrate <NUM>. For example, the portion of the weight of the second plate <NUM> and the portion of the inertial load of the second plate <NUM> that results in a measurable force by the load cell <NUM> may continuously change during the folding motion. A processing system (e.g., the processor <NUM> disclosed below) may be configured to compensate measurements received from the load cells 112a, 112b based on the characteristics, the folding directions, the folding speeds, and/or the folding paths of the first plate <NUM>, the second plate <NUM> and/or of the actuator <NUM>, and/or any other dynamic forces occurring during the folding and/or unfolding processes.

<FIG> is a block diagram of another example flexible substrate testing system <NUM> configured to perform multiple folds on the substrate <NUM>. The example flexible substrate testing system <NUM> of <FIG> includes the first and second plates <NUM>, <NUM>, and further includes a third substrate support structure <NUM>, such as a third plate.

In the example of <FIG>, the axes 126a, 126b are sufficiently offset as to cause multiple folds in the substrate <NUM> (e.g., trifold or more). For example, a third portion <NUM> of the substrate <NUM>, such as a center portion of the substrate <NUM>, is secured to the stationary support structure <NUM>, while the plates <NUM>, <NUM> are actuated to perform folds along multiple axes corresponding to the axes 126a, 126b.

Additionally or alternatively, while single fold axes and dual fold axes are disclosed above, other examples may have three or more folding axes using corresponding substrate support structures (e.g., plates) and corresponding gearing systems to control rotation of the substrate support structures. Furthermore, while the example of <FIG> is configured to fold both sections of the substrate <NUM>, <NUM> toward a same side of the third section <NUM>, in other examples the plates <NUM>, <NUM> and the axes 126a, 126b are configured to fold the sections <NUM>, <NUM> toward opposite sides of the third section <NUM> (e.g., a Z-shaped fold as opposed to a U-shaped fold).

<FIG> is a block diagram of an example implementation of the flexible substrate test system <NUM> of <FIG>. As illustrated in <FIG>, the flexible substrate test system <NUM> includes a test fixture <NUM> and a computing device <NUM>.

The example computing device <NUM> may 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. The computing device <NUM> of <FIG> includes a processor <NUM>, which may be a general-purpose central processing unit (CPU). In some examples, the processor <NUM> may include one or more specialized processing units, such as FPGA, RISC processors with an ARM core, graphic processing units, digital signal processors, and/or system-on-chips (SoC). The processor <NUM> executes machine-readable instructions <NUM> that may be stored locally at the processor (e.g., in an included cache or SoC), in a random access memory <NUM> (or other volatile memory), in a read-only memory <NUM> (or other non-volatile memory such as FLASH memory), and/or in a mass storage device <NUM>. The example mass storage device <NUM> may be a hard drive, a solid-state storage drive, a hybrid drive, a RAID array, and/or any other mass data storage device. A bus <NUM> enables communications between the processor <NUM>, the RAM <NUM>, the ROM <NUM>, the mass storage device <NUM>, a network interface <NUM>, and/or an input/output interface <NUM>.

An example network interface <NUM> includes hardware, firmware, and/or software to connect the computing device <NUM> to a communications network <NUM> such as the Internet. For example, the network interface <NUM> may include IEEE <NUM>. X-compliant wireless and/or wired communications hardware for transmitting and/or receiving communications.

An example I/O interface <NUM> of <FIG> includes hardware, firmware, and/or software to connect one or more input/output devices <NUM> to the processor <NUM> for providing input to the processor <NUM> and/or providing output from the processor <NUM>. For example, the I/O interface <NUM> may include a graphics-processing unit for interfacing with a display device, a universal serial bus port for interfacing with one or more USB-compliant devices, a FireWire, a field bus, and/or any other type of interface. The example extensometer system <NUM> includes a display device <NUM> (e.g., an LCD screen) coupled to the I/O interface <NUM>. Other example I/O device(s) <NUM> may 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.

The computing device <NUM> may access a non-transitory machine-readable medium <NUM> via the I/O interface <NUM> and/or the I/O device(s) <NUM>. Examples of the machine-readable medium <NUM> of <FIG> include optical discs (e.g., compact discs (CDs), digital versatile/video discs (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 media.

The test fixture <NUM> is coupled to the computing device <NUM>. In the example of <FIG>, the test fixture <NUM> is coupled to the computing device via the I/O interface <NUM>, such as via a USB port, a Thunderbolt port, a FireWire (IEEE <NUM>) port, and/or any other type serial or parallel data port. In some examples, the test fixture <NUM> is coupled to the network interface <NUM> and/or to the I/O interface <NUM> via a wired or wireless connection (e.g., Ethernet, Wi-Fi, etc.), either directly or via the network <NUM>.

The test fixture <NUM> includes a frame <NUM>, a load cell <NUM>, material fixtures <NUM>, and a control processor <NUM>. The frame <NUM> provides rigid structural support for the other components of the test fixture <NUM> that perform the test. The load cell <NUM> may implement the load cell <NUM> of <FIG>, and measures force applied to a material under test (e.g., the substrate <NUM>) by an actuator <NUM> via grips <NUM> (e.g., the plates <NUM>, <NUM>).

The actuator <NUM> applies force to the material under test and/or forces displacement of the material under test, while the grips <NUM> grasp or otherwise couple the material under test to the actuator <NUM>.

Example actuators that may be used to provide force and/or motion of a component of the test fixture <NUM> include electric motors, pneumatic actuators, hydraulic actuators, piezoelectric actuators, relays, and/or switches. While the example test fixture <NUM> uses a motor, such as a servo or direct-drive linear motor, other systems may use different types of actuators. For example, hydraulic actuators, pneumatic actuators, and/or any other type of actuator may be used based on the requirements of the system.

The example grips <NUM> include platens, clamps, and/or other types of fixtures, depending on the mechanical property being tested and/or the material under test. The grips <NUM> may be manually configured, controlled via manual input, and/or automatically controlled by the control processor <NUM>.

The test system <NUM> may further include one or more control panels <NUM>, including one or more input devices <NUM>. The input devices <NUM> may include buttons, switches, and/or other input devices located on an operator control panel. For example, the input devices <NUM> may include buttons that control the actuator <NUM> to jog (e.g., position) the grips <NUM> to a desired position, switches (e.g., foot switches) that control the grips <NUM> to close or open (e.g., via another actuator), and/or any other input devices to control operation of the testing test fixture <NUM>.

The example control processor <NUM> communicates with the computing device <NUM> to, for example, receive test parameters from the computing device <NUM> and/or report measurements and/or other results to the computing device <NUM>. For example, the control processor <NUM> may include one or more communication or I/O interfaces to enable communication with the computing device <NUM>. The control processor <NUM> may control the actuator <NUM> to move in a given direction and/or to control the speed of the actuator <NUM>, control the fixture(s) <NUM> to grasp or release a material under test, and/or receive measurements from the displacement transducer <NUM>, the load cell <NUM> and/or other transducers. In some examples, the control processor <NUM> monitors a folding angle by monitoring a motor encoder of the actuator <NUM>, which may be used to establish a folding degree-per-pulse ratio.

The example control processor <NUM> is configured to implement a repetitive motion testing process in which a test specimen (e.g., the substrate <NUM>) is subjected to testing in the test fixture <NUM>. For example, to measure stress on the substrate <NUM> during or after a series of folding and unfolding motions, the control processor <NUM> controls the actuator <NUM> to move the grips <NUM> (e.g., the first and second plates <NUM>, <NUM>) while monitoring the load cell <NUM> to measure stress on the substrate <NUM>.

The example processor <NUM> may determine a static load on the flexible substrate <NUM> based on a load measured by the load cell <NUM> at a completion of the folding or unfolding of the flexible substrate <NUM>. The static load measurement may occur after a relaxation time has been permitted to expire to enable the substrate <NUM> to relax following a folding or unfolding process. Additionally or alternatively, the example processor <NUM> may determine a dynamic load on the flexible substrate <NUM> based on loads measured by the load cell <NUM> during the folding or unfolding of the flexible substrate <NUM>. The example processor <NUM> may perform compensation of measurements from the load cell(s) <NUM>, such as removing the effects of weight of the first plate <NUM>, and/or weight and inertial load of the second plate <NUM>, from the load measurements.

<FIG> is a perspective view of an example implementation of the flexible substrate test system <NUM> of <FIG>, illustrating the first and second plates <NUM>, <NUM> in an open or flat position. <FIG> is a perspective view of the example flexible substrate test system <NUM> of <FIG>, in the open or flat position and omitting the first and second plates. <FIG> is a perspective view of the example flexible substrate test system <NUM> of <FIG>, in an intermediate position (e.g., between the open position and the closed position). <FIG> is another perspective view of the example flexible substrate test system of <FIG>, in the intermediate position. <FIG> is a perspective view of the example flexible substrate test system <NUM> of <FIG>, in a closed or folded position. <FIG> is a side elevation view of the example flexible substrate test system <NUM> of <FIG>, in the closed or folded position.

The example translation linkages 114a, 114b each include a first four-bar linkage 302a, 302b, a second four-bar linkage 304a, 304b, and a frame 306a, 306b. The frame 306a and the load cell 112a are stationary with respect to each other by attachment to a rotational assembly 310a. The frame 306b and the load cell 112b are stationary with respect to each other by attachment to a rotational assembly 310b. The first and second four-bar linkages 302a, 302b, 304a, 304b are each configured to attach the first plate <NUM> or second plate <NUM> via the innermost links. The first and second four-bar linkages 302a, 304a limit movement of the first plate <NUM> in directions parallel to the surface of the first plate <NUM> on which the substrate <NUM> is mounted, while permitting loads from the first plate <NUM> to be transferred to the load cell 112a (e.g., via an extension post 308a coupled to the load cell 112a) in a direction perpendicular to the surface of the first plate <NUM> (illustrated as direction Z in <FIG>).

To avoid overloading of the load cells 112a, 112b, the frames 306a, 306b include stopping points configured to prevent the first and second four-bar linkages <NUM>, <NUM> and/or the first plate <NUM> or second plate <NUM> from traveling toward the load cell 112a, 112b beyond the stopping point. The stopping point may be implemented using, for example, a pin or other rigid fastener configured to contact an underside of the first and/or second four-bar linkages 302a, 302b, 304a, 304b, a top surface of the frame 306a, 306b, a bumper or rigid offset coupled to a top surface of the frame 306a, 306b to provide the stopping point via contact with first plate <NUM> or the second plate <NUM>, and/or any other technique.

The rotational arms 301a, 301b are configured to rotate and translate the first plate <NUM> and the second plate <NUM> to fold and unfold the substrate <NUM>. The rotational arms 301a, 301b are coupled to axes of rotation 312a, 312b (e.g., pivot points). An actuator may rotate both of the rotational arms 301a, 301b simultaneously by driving an input shaft <NUM>. The input shaft <NUM> is coupled to secondary shafts 316a, 316b, which drive respective gearing systems 318a, 318b coupled to the rotational arms 301a, 301b. In some examples, the gear ratios are the same between the input shaft <NUM> and the rotational arms 301a, 301b to cause both plates <NUM>, <NUM> to fold simultaneously and proportionally.

While the example of <FIG> includes the gearing systems 318a, 318b to define the folding path of the substrate <NUM>, in other examples the guide may be different. For example, other guides may include having multiple gears, in which a first gear is free to spin and is aligned with the edge of the first side of the substrate <NUM>, and a second gear is meshed with the first gear and fixed with respect to the second half of the substrate <NUM>. Other example guides may include combinations of two linear actuators arranged perpendicular to each other, with one linear actuator in a combination mounted to the other linear actuator. The first plate <NUM> and the second plate <NUM> are attached to respective ones of the actuator combinations, and could move freely in an x-y plane and trace out the folding path. Multiple linear actuators may enable the guide to implement different types of paths, including folds of different radii and/or non-circular folds. Some other example guides may include a series of linkages defining the folding path.

<FIG> is a partially exploded view of the translation linkage of <FIG>. In particular, the example translation linkage 114a is shown with inner linkages <NUM>, <NUM> of the four-bar linkages <NUM>, <NUM> separated from intermediate linkages <NUM>, <NUM>, <NUM>, <NUM>, respectively. The intermediate linkages <NUM>-<NUM> couple the inner linkages <NUM>, <NUM> to the frame <NUM>, which serves as a portion of the four-bar linkages <NUM>, <NUM>.

<FIG> is a flowchart representative of an example method <NUM> to measure loads on a flexible substrate, which may be performed by the example flexible substrate test systems of FIGS. The example method <NUM> is disclosed below with reference to <FIG> and <FIG>.

At block <NUM>, the processor <NUM> and/or the control processor <NUM> calibrate the load cell(s) <NUM>, <NUM> to compensate for the weight(s) of the first and/or second substrate support structure(s) (e.g., the first plate <NUM>, the second plate <NUM>), the translation linkage <NUM>, and/or any other forces that affect the measurement by the load cell(s) <NUM>, <NUM>.

At block <NUM>, the first substrate support structure (e.g., the first plate <NUM>) holds a first portion of the flexible substrate <NUM> stationary. At block <NUM>, the second substrate support structure (e.g., the second plate <NUM>) holds a second portion of the flexible substrate <NUM>.

At block <NUM>, the processor <NUM> and/or the control processor <NUM> determine whether to fold the flexible substrate <NUM>. For example, the processor <NUM> may determine whether a folding cycle (e.g., folding and unfolding) is to be performed. If the folding is not to be performed (block <NUM>), control iterates to block <NUM> to await folding.

When folding is to be performed (block <NUM>), at block <NUM> the processor <NUM> and/or the control processor <NUM> control the actuator <NUM> to move the first and second substrate support structures (e.g., the first and second plates <NUM>, <NUM>) in a folding direction to fold the flexible substrate <NUM>. In some examples, a gearing system or other guide may be used to control the bend radius and/or folding path of the flexible substrate <NUM> during the folding. At block <NUM>, the load cell(s) 112a, 112b, <NUM> measure dynamic load(s) on the flexible substrate <NUM> during the folding and/or measure static load(s) on the flexible substrate <NUM> after folding.

At block <NUM>, the processor <NUM> and/or the control processor <NUM> determine whether to unfold the flexible substrate <NUM>. If the unfolding is not to be performed (block <NUM>), control iterates to block <NUM> to await unfolding.

When unfolding is to be performed (block <NUM>), at block <NUM> the processor <NUM> and/or the control processor <NUM> control the actuator <NUM> to move the first and second substrate support structures in an unfolding direction to unfold the flexible substrate <NUM>. In some examples, a gearing system or other guide may be used to control the bend radius and/or folding path of the flexible substrate <NUM> during the unfolding. At block <NUM>, the load cell(s) <NUM>, <NUM> measure dynamic load(s) on the flexible substrate <NUM> during the unfolding and/or measure static load(s) on the flexible substrate <NUM> after unfolding.

At block <NUM>, the processor <NUM> and/or the control processor <NUM> determine whether to repeat the folding cycle. For example, the flexible substrate <NUM> may be subject to a testing process involving multiple folding cycles. If the folding cycle is to be repeated (block <NUM>), control returns to block <NUM>. If the folding cycle is not to be repeated (block <NUM>), the example method <NUM> ends.

Claim 1:
A flexible substrate testing system (<NUM>), comprising:
a first substrate support structure (<NUM>) configured to hold a first portion of a flexible substrate (<NUM>) under test;
a second substrate support structure (<NUM>) configured to hold a second portion of the flexible substrate (<NUM>);
one or more actuators (<NUM>) configured to move the first and second substrate support structures (<NUM>, <NUM>) at respective angles to fold the flexible substrate (<NUM>);
a first load cell (112a) configured to measure loads on the first substrate support structure (<NUM>) and a second load cell (112b) configured to measure load on the second substrate support structure (<NUM>) while the actuator (<NUM>) moves the first substrate support structure (<NUM>) and the second substrate support structure (<NUM>), and
a single input shaft (<NUM>);
a first secondary shaft (316a) configured to move the first substrate support structure (<NUM>) and
a second secondary shaft (316b) configured to move the second substrate support structure (<NUM>),
wherein the one or more actuators (<NUM>) are configured to move the first and second substrate support structures (<NUM>, <NUM>) simultaneously by driving the single input shaft (<NUM>),
wherein the input shaft (<NUM>) is coupled to the first secondary shaft (316a) and to the second secondary shaft (316b).