Method and system for controlling flow drill screw based on acceleration

Abstract

The invention provides a method and system for controlling a flow drill screw based on acceleration. A method of installing a flow drill screw (FDS) into a substrate includes: engaging the FDS with an automatic tool; operating the tool at a first setting to drive the FDS into the substrate by causing the substrate to flow to allow the FDS to penetrate the substrate, the first setting configured to rotate the FDS at a first rotational speed and apply a first axial feed force, the first setting configured to cause the substrate to flow to allow the FDS to penetrate the substrate; and switching the automated tool from the first setting to a second setting in response to the controller analyzing the axial acceleration data of the FDS, where the second setting is configured to rotate the FDS at a second rotational speed and apply a second axial feed force, where the second rotational speed is less than the first rotational speed.

Description

Technical Field

[0001] The present disclosure relates to a method and system for installing a flow drill screw. Background Art

[0002] The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.

[0003] A flow drill screw (FDS) is a specific type of screw used to create a threaded joint between multiple substrates (one of which is a lower substrate) without using part preparation such as tapping or drilling holes in the lower substrate. The lower substrate is typically metal, and the total number of substrates is typically two to four, but other numbers can be used. The upper substrate may or may not have a preformed through hole.

[0004] A typical FDS has a distal portion without threads or cutting edges and is configured to penetrate a substrate by locally heating the substrate using heat generated by rotational friction and axial pressure on the FDS. As the FDS penetrates the substrate, it forms threads in the substrate.

[0005] In a typical FDS process, the automatic tool is controlled to rotate the FDS at a high revolutions per minute (RPM) rate while applying a high axial force toward the substrate. The typical FDS automatic tool does not directly control the axial position. This high RPM, high force produces friction that heats the substrate, and is maintained until the automatic tool detects a trigger condition corresponding to the start of penetration from the data measured in real time. Immediately after detecting the trigger condition, the controller of the automatic tool sends a signal to notify the automatic tool to reduce RPM and force. Therefore, the automatic tool reduces RPM and force before the thread forming part of the FDS enters the substrate, so that the thread formation and the tightening of the FDS against the substrate can occur at a lower RPM and force. It should be generally understood in the art that once penetration is achieved, RPM and force should be reduced, but not before penetration. It is generally accepted in the art that if the FDS has not been fully penetrated before the RPM and force drop, it is very likely that the FDS will not penetrate the lower substrate at all in the end. This is because the lower speed and force do not generate enough heat or force to continue to penetrate the metal and deform the metal. Additionally, those skilled in the art generally recognize that it is important to reduce the RPM and force before the thread forming portion enters the bottom substrate so that there is adequate process control (e.g., drive deceleration and final tightening) as the process nears completion and the substrate is allowed to cool slightly before the thread forming portion enters the substrate and bushing area. It is also generally understood that it is critical that the RPM and force are low enough at the typical drop point of the process to have an acceptable ability to stop the process when the target torque value is reached without overshooting and stripping the joint.

[0006] It is important that the torque applied to the FDS during the penetration portion of the installation process does not rise above the rated torque value of the FDS.

[0007] The trigger conditions are typically axial position (ie, depth) or axial velocity (ie, depth gradient) thresholds. While these typical trigger conditions may be suitable for some applications, there is room for improvement.

[0008] The teachings of the present disclosure address these and other problems of installing a FDS into a substrate. Summary of the invention

[0009] This section provides a general summary of the disclosure and is not a comprehensive disclosure of its full scope or all of its features.

[0010] In one form, the present disclosure provides a method of installing a flow drill screw (FDS) into a substrate, the method comprising: engaging the FDS with an automatic tool; operating the automatic tool in a first setting to drive the FDS into the substrate by causing the substrate to flow to allow the FDS to penetrate the substrate, the first setting being configured to rotate the FDS at a first rotational speed and apply a first axial feed force on the FDS, the first setting being configured to cause the substrate to flow to allow the FDS to penetrate the substrate; and switching the automatic tool from the first setting to a second setting in response to a controller analyzing axial acceleration data of the FDS, wherein the second setting is configured to rotate the FDS at a second rotational speed and apply a second axial feed force to the FDS, wherein the second rotational speed is less than the first rotational speed.

[0011] According to a variety of alternative forms (which may be used alone or in any combination with the methods of the above paragraphs), the method further includes detecting position data of the FDS while operating the automatic tool in the first setting, and calculating an axial acceleration of the FDS based on the detected position data; the method further includes applying a smoothing filter to the detected position data to generate a smoothed position data set, wherein the smoothed position data is used to calculate the axial acceleration; the method further includes calculating axial velocity data based on the detected position data, and applying a smoothing filter to the calculated axial velocity data to generate a smoothed axial velocity data set, wherein the smoothed axial velocity data set is used to calculate the axial acceleration; in response to the controller determining that the axial acceleration of the FDS exceeds a predetermined axial acceleration value, switching the automatic tool from the first setting to the second setting is executed, and the predetermined axial acceleration value is between 1,000 and 30,000 mm / s 2; axial acceleration data is measured by an accelerometer; the method further comprises positioning one or more additional substrates adjacent to the substrate so that the FDS clamps the one or more additional substrates to the substrate after completing the method; the first rotational speed is between 1,500 and 12,000 RPM (inclusive), and the first axial feed force is between 0.5 and 4 kN (inclusive), wherein the second rotational speed is between 500 and 4,000 RPM (inclusive), and the second axial feed force is between 0.25 and 1.25 kN (inclusive).

[0012] In a further form, the present disclosure provides a method of installing a flow drill screw (FDS) into a substrate, the method comprising: engaging the FDS with an automatic tool; operating the automatic tool in a first setting to drive the FDS into the substrate by causing the substrate to flow to allow the FDS to penetrate the substrate, the first setting being configured to rotate the FDS at a first rotational speed and apply a first axial feed force on the FDS, the first setting being configured to cause the substrate to flow to allow the FDS to penetrate the substrate; detecting position data of the FDS while operating the automatic tool in the first setting; calculating axial acceleration data based on the detected position data; and switching the automatic tool from the first setting to a second setting based on a maximum axial acceleration value or the axial acceleration data exceeding a predetermined axial acceleration value, wherein the second setting is configured to rotate the FDS at a second rotational speed and apply a second axial feed force to the FDS, wherein the second rotational speed is less than the first rotational speed.

[0013] According to multiple alternative forms (which can be used alone or in any combination with the methods of the above paragraphs), the method also includes applying a smoothing filter to the detected position data to generate a smoothed position data set, wherein the smoothed position data set is used to calculate the axial acceleration data; the method also includes calculating the axial velocity data based on the detected position data, applying the smoothing filter to the calculated axial velocity data to generate a smoothed axial velocity data set, wherein the smoothed axial velocity data set is used to calculate the axial acceleration; switching the automatic tool from the first setting to the second setting is based on the axial acceleration data exceeding the predetermined axial acceleration data, wherein the predetermined axial acceleration value is between 500 and 50,000 mm / mm / s 2 The method further comprises positioning one or more additional substrates adjacent to the substrate so that the FDS clamps the one or more additional substrates to the substrate after completing the method; the first rotational speed is between 1,500 and 12,000 RPM (inclusive), and the first axial feed force is between 0.5 and 4 kN (inclusive), wherein the second rotational speed is between 500 and 4,000 RPM (inclusive), and the second axial feed force is between 0.25 and 1.25 kN (inclusive).

[0014] In yet another form, the present disclosure provides a system for installing a flow drill screw (FDS), the system comprising: a drive unit configured to rotate the FDS about an axis at a certain rotational speed while applying an axial feed force on the FDS to drive the FDS through at least one substrate; and a controller configured to change the rotational speed and the axial feed force in response to a measured or calculated axial acceleration of the FDS exceeding a predetermined axial acceleration value.

[0015] According to a number of alternative forms (which may be used alone or in any combination with the methods of the above paragraphs), the system further comprises a sensor configured to detect position data of the FDS, wherein the controller is configured to calculate an axial acceleration of the FDS based on the detected position data of the FDS; the controller is configured to apply a smoothing filter to the position data to generate a smoothed position data set, wherein the axial acceleration is calculated using the smoothed position data set; the controller is configured to reduce the rotational speed and the axial feed force from a first rotational speed and a first axial feed force to a second rotational speed and a second axial feed force in response to the axial acceleration of the FDS exceeding a predetermined axial acceleration value; the first rotational speed is between 1,500 and 12,000 RPM (inclusive) and the first axial feed force is between 0.5 and 4 kN (inclusive), wherein the second rotational speed is between 500 and 4,000 RPM (inclusive) and the second axial feed force is between 0.25 and 1.25 kN (inclusive); the predetermined axial acceleration value is between 500 and 3,000 mm / s 2 between.

[0016] Further areas of applicability will become apparent from the description provided herein.It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order that the present disclosure may be better understood, various forms of the present disclosure will now be described by way of example with reference to the accompanying drawings, in which:

[0018] FIG1 is a side view of an example flow drill screw (FDS);

[0019] Figure 2 is a series of sequential stages of the FDS of FIG. 1 during an installation process according to the teachings of the present disclosure;

[0020] Figure 3 is a graph showing torque and screw position for an installation process for a flow drill screw in accordance with the teachings of the present disclosure;

[0021] Figure 4is a graph showing axial velocity, screw position, and erroneous screw position measurements for a flow drill screw installation process in accordance with the teachings of the present disclosure;

[0022] Figure 5 yes Figure 4 Detailed view of a portion of a graph showing how axial velocity control can correct erroneous screw position measurements;

[0023] Figure 6 is a graph showing a screw velocity diagram of a flow drill screw installation process according to the teachings of the present disclosure, showing the magnitude of the error between the velocity calculated by taking a real-time derivative of a screw position measurement and the smoothed velocity data generated by smoothing the calculated real-time derivative;

[0024] Figure 7 is similar to Figure 6 , but the graph also shows the acceleration of the screw calculated by taking the derivative of the smoothed velocity data in accordance with the teachings of the present disclosure; and

[0025] Figure 8 is a flow chart illustrating a method of installing a flow drill screw according to the teachings of the present disclosure.

[0026] The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. DETAILED DESCRIPTION

[0027] The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate the same or corresponding parts and features.

[0028] Referring to FIG. 1 , a typical FDS 10 is shown, and the FDS has a head 14 and a shank 18 disposed about a rotation axis 22. The head 14 includes a clamping portion 26 and a tool engagement portion 30. The clamping portion 26 extends radially outward from the shank 18. The tool engagement portion 30 is configured to be clamped by an automatic tool to rotate the FDS about its rotation axis 22. The shank 18 extends in an axial direction from the clamping portion 26 to a tip 34. Between the tip 34 and the clamping portion 26 are a threaded portion 38, a thread forming portion 42, a cylindrical portion 46, and an end portion 50. As shown, the tip 34 is generally round, relatively smooth, and relatively blunt, but some typical FDSs may have a more pointed tip. The end portion 50 includes the tip 34 and tapers radially outward toward the cylindrical portion 46. The end portion 50 and the cylindrical portion 46 are not threaded. In some forms, the cylindrical portion 46 has a constant diameter. In other forms, the cylindrical portion 46 has a diameter that increases more gradually than the end portion 50. The threaded portion 38 has at least one full thread profile 54 disposed about the axis 22. The thread forming portion 42 is axially located between the cylindrical portion 46 and the threaded portion 38 and has at least one partial thread profile 58 that coincides with the at least one full thread profile 54 but tapers radially inwardly from the full thread profile 54 toward the cylindrical portion 46. In other words, the thread forming portion 42 has a partial depth thread profile that has a diameter (i.e., a major thread diameter) that narrows as the distance from the threaded portion 38 increases. In some forms not shown, a typical FDS may have a second cylindrical portion between the clamping portion 26 and the threaded portion 38.

[0029] Refer to Figure 1 and Figure 2 , sequential stages or states (labeled 1 to 6) of the FDS 10 during an installation process performed by an installation tool 110 are shown. The tool 110 is an automated tool that includes a driver 114, one or more sensors 118 (shown only in stage 1 for ease of illustration), and a controller 122 (shown only in stage 1 for ease of illustration). The driver 114 is configured to engage the tool engagement portion 30 of the FDS 10 to rotate the FDS 10 about its rotational axis 22 while applying an axial force toward a first substrate 210. The controller 122 is in communication with the driver 114 and the sensor 118, and is configured to control the operation of the driver 114 and receive input from the sensor 118.

[0030] The first substrate 210 may be any suitable material formed using any suitable process. In one form, the first substrate 210 is aluminum or an aluminum alloy. In another form, the first substrate 210 is magnesium or a magnesium alloy. In yet another form, the first substrate 210 is steel or a steel alloy. In yet another form, the first substrate 210 is a composite material. In some forms, the first substrate 210 may be a stamped sheet of material. In other forms, the first substrate 210 may be a casting. In other forms, the first substrate 210 may be an extrusion. In yet other forms, the first substrate may be forged.

[0031] Although not specifically shown, the drive 114 includes a motor (e.g., an electric motor, a hydraulic motor, or a pneumatic motor) configured to provide rotation and controlled by the controller 122. Although not specifically shown, the drive 114 also includes an actuator that can be actuated by any suitable power source (e.g., electric, hydraulic, or pneumatic power) to apply an axial force. The actuator is controlled by the controller 122. In one form, the actuator is a pneumatic actuator (e.g., a pneumatic cylinder) for applying an axial force. In one form, the drive 114 can be optionally disposed on a robot arm (not shown) or a base (not shown), and the controller 122 can be configured to control the movement of the robot arm.

[0032] In the first stage, the FDS 10 is rotated while an axial force is applied on the FDS 10 in an axial direction towards the first substrate 210. In this first or initial stage, the first substrate 210 does not have any through holes at the location where the FDS 10 is to be mounted.

[0033] In the example provided, the first substrate 210 is a lower substrate and the second substrate 214 is an upper substrate that is disposed on top of the first substrate 210 and is configured to be clamped to the first substrate 210 by the clamping portion 26 of the FDS10. In the example provided, the second substrate 214 defines a pre-formed hole 218 having a diameter that is larger than the handle 18 but smaller than the clamping portion 26, so that the clamping portion 26 can clamp the second substrate 214 against the first substrate 210. Although only one second substrate 214 is shown, additional substrates may be used. For example, in some configurations not specifically shown, in addition to the second substrate 214, the FDS10 may clamp one, two, three, four, or more additional substrates to the first substrate 210. These additional substrates may optionally have pre-formed through holes, or the FDS may form holes therethrough. In Figure 2 In the example shown, the FDS 10 completely penetrates the first substrate 210 in the final stage 6 .

[0034] Although the first substrate 210 is Figure 2The first substrate 210 is shown as being thinner than the second substrate 214 , but in another form not specifically shown, the first substrate 210 may be thicker than the second substrate 214 .

[0035] In another alternative configuration not specifically shown, the first substrate 210 may be a top substrate and the second substrate may be a bottom substrate, but without the preformed holes 218 ( Figure 2 ). In this alternative configuration, the FDS 10 may drill through the first substrate 210 and drill through the second substrate to clamp the first substrate 210 to the second substrate.

[0036] In yet another alternative configuration, not specifically shown, the second substrate may be omitted entirely, and the FDS 10 may be connected only to the first substrate 210. In some such forms, the FDS 10 may include connection features (not shown, e.g., hooks, eyes, magnets, surfaces for receiving adhesive, etc.) such that mating features on another component may be coupled to the FDS 10 after the FDS 10 is attached to the first substrate 210.

[0037] Return to Figure 1 and Figure 2 In the first stage 1 (also referred to as the heating stage), the rotational speed and axial force of the tool 110 are configured to generate friction at the tip 34 to locally heat the substrate to a sufficient degree to melt or soften the substrate to a flowable state. Typically, the tool 110 continues to rotate the FDS 10 and apply axial pressure thereto until the FDS 10 is fully tightened in the final (e.g., sixth) stage 6 (also referred to as the tightening stage).

[0038] In stage 2 (also referred to as the penetration stage), the end portion 50 of the FDS 10 begins to penetrate into the first substrate 210, but the cylindrical portion 46 has not yet entered the first substrate 210. In stage 3, the cylindrical portion begins to enter the first substrate 210, but the thread forming portion 42 has not yet entered the first substrate 210. Stage 3 is also referred to as the hole forming stage because this is the stage where a small diameter hole is formed in the first substrate 210. It should be understood that although stage 3 is shown as the tip 34 completely penetrating the first substrate 210, depending on the thickness of the first substrate 210, the tip 34 may still be within the first substrate 210. In stage 4, the thread forming portion 42 begins to penetrate into the first substrate 210, but the threaded portion 38 has not yet entered the first substrate 210. Stage 4 is also referred to as the thread forming stage because the thread forming portion 42 forms threads at this stage. In stage 5, the threaded portion 38 begins to penetrate the first substrate 210. During stage 5, also referred to as the drive deceleration stage, the threaded portion 38 is screwed into the threads formed by the thread forming portion 42, and the advancement of the FDS 10 is advanced axially into the first substrate 210 until the clamping portion 26 engages the second substrate 214 (or the clamping portion 26 engages the first substrate 210 in a form where the second substrate is located below the first substrate 210) to begin the final stage 6. In stage 6, also referred to as the tightening stage or the final tightening stage, the FDS 10 is tightened until fully tightened.

[0039] In some forms, the sensor 118 may detect a predetermined end trigger condition, and the controller 122 controls the driver 114 to tighten the FDS 10 until the predetermined end trigger condition. In one form, the sensor 118 may include a torque sensor, and the end trigger condition may be a predetermined final torque value. The predetermined final torque value is less than the torsional strength rating of the FDS 10. In another form, the sensor 118 may include a depth or position sensor to detect position data, and the predetermined end trigger condition may be the depth or position of the FDS 10 and / or a predetermined torque value.

[0040] refer to Figure 3 , shows torque and screw axial position (i.e., depth) over time during the installation process of the FDS 10. In the graph, the maximum screw position (i.e., at line 410) refers to the position where the tip 34 of the FDS 10 initially contacts the first substrate 210, and the screw position of 0 mm (zero millimeters) refers to the final position, where the clamping portion 26 clamps the second substrate 214 against the first substrate 210 (or in a form where the second substrate is below the first substrate 210, the clamping portion 26 engages the first substrate 210).

[0041] refer to Figure 2 and Figure 3, Phase 1 (ie, the heating phase) begins at line 410 and proceeds to line 414. During this phase, the torque rises, but the axial position of the FDS 10 remains stationary as heat accumulates.

[0042] Phase 2 (i.e., the penetration phase) begins at line 414. During this phase, as the tip 34 begins to penetrate the first substrate 210, the torque continues to rise to a first peak 418, and the axial position of the FDS 10 slowly advances downward (i.e., toward zero millimeters). As shown, as the first substrate 210 continues to soften due to the accumulation of heat, the axial position of the FDS 10 may begin to slowly move downward while the tip 34 continues to penetrate the first substrate 210.

[0043] Stage 3 (ie, the hole formation stage) begins at line 422. During this stage, as the cylindrical portion 46 enters the first substrate 210, the torque drops and the axial position of the FDS 10 moves rapidly downward.

[0044] Stage 4 (i.e., the thread forming stage) begins at line 426. During this stage, as the thread forming portion 42 enters and forms threads in the first substrate 210, the torque quickly rises to a second peak 430, and the axial position of the FDS 10 continues downward, albeit at a slower rate than during Stage 3.

[0045] Phase 5 (i.e., the drive deceleration phase) begins at line 434. During this phase, the torque decreases to a substantially steady state as the axial position of the FDS 10 continues downward via the mating action of the threaded portion 38 and the threads formed in the first substrate 210 by the thread forming portion 42 during Phase 4.

[0046] Phase 6 (ie, the final tightening phase) begins at line 438. During this phase, the torque rises sharply while the axial position of the FDS 10 is maintained substantially at zero millimeters of torque rise until the end trigger condition is met and the controller 122 stops the rotation of the driver 114.

[0047] At the beginning of stage 1 (line 410), tool 110 is controlled to operate at a first setting, under which tool 110 is controlled to operate at a first rotational speed and a first axial feed force. At a point between the beginning of stage 3 (line 422) and the beginning of stage 6 (line 438), tool 110 is controlled to switch from the first setting to a second setting, wherein tool 110 is controlled to operate at a second RPM and a second axial feed force (which may optionally be the same or different from the first axial feed force). The first rotational speed is also referred to herein as a high rotational speed, and may be in the range of 1,500 to 11,000 RPM (including end values). In one form, the first rotational speed is more specifically in the range of 2,000 to 8,000 RPM (including end values). In another form, the first rotational speed is more specifically in the range of 6,000 to 11,000 RPM (including end values). The first axial feed force is also referred to as a high axial feed force in this article, and is in the range of 0.5 to 2.5 kilonewtons (kN) (including end values). In one form, the first axial feed force can be in the range of 1 to 2kN. The second rotational speed is also referred to as a low rotational speed in this article, and is in the range of 500 to 4,000RPM (including end values). In one form, the second rotational speed can be within this range but less than the first rotational speed, but other configurations can be used. The second axial feed force is also referred to as a low axial feed force in this article, and is in the range of 0.25 to 1.25kN (including end values). In one form, the second axial feed force can be within this range but less than the first axial feed force, but other configurations can be used. For example, in another form, the second axial feed force can be equal to or greater than the first axial feed force.

[0048] refer to Figure 4 , two data sets of screw axial position (i.e., depth) of the same screw over time during the installation process of the FDS 10 are shown. A first position curve 510 is formed from a first screw position data set measured by the sensor 118. A second position curve 514 is formed from a second screw position data set measured by the sensor 118. The difference 518 in the measured screw position data may be due to any number of factors (e.g., calibration errors between the two position sensors 118).

[0049] Figure 4 Also shown is the axial velocity 522 of the FDS 10 as a function of time during the installation process. Figure 4As shown, the axial velocity 522 is the same for both position curves 510, 514. It has been found that even when the same sensor 118 is used but two position curves are produced for the same general process with subsequent screws, the axial velocity is actually the same or has a small difference (e.g., where the difference 518 in the measured position data is due to other factors such as dimensional tolerances in the FDS 10, tolerances in the first substrate 210, and / or tolerances in the second substrate 214).

[0050] refer to Figure 5 , when a specific axial position (e.g., depth) value is used as a trigger point (e.g., threshold 610) to switch from a first setting (e.g., high rotational speed and high axial feed force) to a second setting (e.g., low rotational speed and low axial feed force), an error may result (illustrated by the distance 614 between the time when the first position data 510 intersects the value 610 and the time when the second position data 514 intersects the value 610). However, if the threshold 610 is a specific axial speed value rather than an axial position value, it has been found that this error is eliminated (as in the example shown) or greatly reduced while ensuring that the process can function as intended.

[0051] However, it has been found that due to many factors (e.g., signal propagation time, signal processing time, sampling speed, rotational momentum in the system), these typical trigger conditions (e.g., position thresholds or axial velocity thresholds) may ultimately be lagging indicators of the true position of the FDS 10. In other words, by the time the actual rotation and axial force of the FDS 10 are reduced (compared to the time when the controller sends a signal to reduce the rotation and axial force), the FDS 10 may have already exceeded the most desired axial position relative to the substrate.

[0052] refer to Figure 6, shows real-time velocity (i.e., depth gradient) data 710 and real-time smoothed axial velocity data 714 of the FDS10 over time during the installation process. As used herein, "velocity" refers to "axial velocity". The velocity data 710 is calculated in real time by the controller 122 by obtaining the first derivative of the axial position data (e.g., axial position curve 510 or 514) detected by the sensor 118. The controller 122 can calculate the velocity data 710 using the measured axial position data in raw form or smoothed form (i.e., after applying a smoothing filter to the measured axial position data; any suitable smoothing filter, such as those discussed below, can be used). As can be seen from the relatively jagged (i.e., noisy) graph of the velocity data 710, the sensitivity, sampling rate, and tolerance of the position sensor 118 and other noise that causes interference may cause a lot of variability between values ​​adjacent in time in the data set. This variability may also make it difficult to set an axial velocity threshold trigger value that will repeatedly trigger the FDS10 at the same actual position relative to the substrate 210, 214.

[0053] Smoothed speed data 714 is calculated in real time by the controller 122 by passing the speed data 710 through a smoothing filter. The smoothing filter can be any suitable smoothing filter. Some non-limiting examples of smoothing filters are moving average smoothing filters, local regression smoothing filters, exponential smoothing smoothing filters, Kalmann smoothing filters, and Savitzky-Golay smoothing filters.

[0054] like Figure 6 As can be seen in the figure, the smoothed velocity data 714 ends up being offset in magnitude and phase / time relative to the velocity data 710. Some of this offset may also be due to processing time in calculating these values ​​in real time. In addition, when the rate of change of the velocity data 710 is rapid, as is the case with an FDS installation, the time error 718 and magnitude error 722 between the velocity data 710 and the smoothed velocity data 714 may be significant. The time error also causes the velocity threshold to be an even more lagging indicator of the actual characteristic of the FDS 10 (e.g., actual axial position).

[0055] refer to Figure 7, the controller 122 is configured to calculate the axial acceleration data set 810 in real time by obtaining the derivative of the smoothed velocity data 714. In other words, the acceleration data 810 is based on the second-order derivative of the position data detected by the sensor 118. In another form, the controller 122 can directly calculate the second-order derivative of the measured position data without first applying a smoothing filter to the velocity data 710 and / or the position data, and can optionally apply the smoothing filter to the calculated second-order derivative data set to obtain the acceleration data set used to determine the trigger condition.

[0056] In yet another form, the sensor 118 may be an accelerometer and the measured data may be acceleration directly, which may optionally be passed through a smoothing filter.

[0057] Surprisingly, it has been discovered that using screw axial acceleration data (e.g., acceleration data set 810) and checking when it reaches a threshold acceleration value (e.g., trigger value 814) can be more accurate and more repeatable than using a threshold axial position or axial velocity value, while also providing a leading indicator. In other words, the screw acceleration data 810 provides a curve that can repeatably produce an identifiable threshold trigger that occurs early enough in the installation process that the controller 122 can act on the threshold so that delays in data processing, signal propagation, and physical momentum of the components can be compensated. In other words, setting the trigger to the screw acceleration threshold results in triggering the controller 122 to send a control signal earlier so that the FDS 10 actually physically achieves the second rotational speed and the second axial feed force faster than would normally be possible at the axial position or axial velocity value thresholds. The value of the trigger value at line 814 is between 0.01 and 0.08. Figure 7 The values ​​of the acceleration values ​​shown in the figures are shown for illustration purposes and may be selected at other acceleration values ​​than those shown. Actual acceleration thresholds may also differ due to the data collection and smoothing processes implemented. For example, different data collection and / or smoothing processes may change the values ​​of the data set being used, and the thresholds may be selected accordingly. Likewise, the values ​​of the data graphs or curves shown in the graphs of the accompanying drawings are also shown for illustration purposes and may differ depending on the data collection and / or smoothing processes used.

[0058] In one form, the screw acceleration threshold 814 may be between 50 and 300 mm / s. 2 , but other ranges (e.g., such as 1,000 to 30,000 mm / s) may be used. 2 (inclusive of end values), or 500 to 50,000 mm / s 2 (inclusive of end values), or 500 to 30,000 mm / s 2(including end values)), depending on the data collection and / or smoothing process used. In one configuration of this form, the controller 122 immediately sends a control signal to switch to the second setting when it is determined that the screw axial acceleration data 810 has reached or exceeded the screw acceleration threshold value 814. In another configuration of this form, the controller 122 immediately starts a predetermined time delay when it is determined that the screw axial acceleration data 810 has reached or exceeded the screw acceleration threshold value 814 and then immediately sends a control signal to switch to the second setting at the end of the time delay. In some forms, the time delay can be between 1 and 30ms, including the end values. In another configuration of this form, the controller 122 does not use a predetermined time delay, but instead uses a predetermined axial position delay. In other words, the controller 122 immediately starts analyzing the measured axial position data when it is determined that the screw axial acceleration data 810 has reached or exceeded the screw acceleration threshold value 814 and then immediately sends a control signal to switch to the second setting when the axial position data indicates that the FDS10 has moved a predetermined axial distance after the threshold value 814. In some forms, the predetermined axial distance may be between 0.5 and 10 mm, inclusive.

[0059] In another form not specifically shown, the screw acceleration threshold 814 may be set (e.g., Figure 7 The maximum axial acceleration achieved (at point 818 of the controller 122) may be set based on the determination of the maximum axial acceleration. In other words, the controller 122 may be configured to switch to the second setting when it is determined that the maximum axial acceleration has been achieved. In one configuration of this form, the controller 122 may switch immediately when it is determined that the maximum axial acceleration has been achieved. In another configuration, the controller 122 may be configured to switch immediately after a predetermined time delay after determining the maximum value. In another configuration, the controller 122 may be configured to switch immediately after a predetermined axial position delay after determining the maximum value. The controller 122 may determine the maximum axial acceleration in any suitable manner, including but not limited to any one of the following examples (alone or in any suitable combination thereof). In the example, the controller 122 compares each acceleration value with a subsequent acceleration value, and determines that the maximum value is a value having at least two subsequent acceleration values ​​lower than it. In another example, the controller 122 obtains the derivative of the acceleration data value in real time, and determines that the maximum axial acceleration is the value when the derivative (i.e., slope) of the acceleration curve 810 begins to become negative. In another example, the controller 122 can fit a mathematical model (e.g., a moving average) to the acceleration data and predict when the acceleration will reach a maximum value. In the example where the controller 122 predicts the maximum acceleration, the controller 122 can switch to the second setting at a predetermined time before the maximum value so that delays in signal processing, momentum, etc. are compensated.

[0060] In yet another form, not specifically shown, the screw acceleration threshold 814 may be set based on when the axial acceleration reaches zero (i.e., where the axial acceleration begins to be negative so that the axial velocity slows down). In this form, the controller 122 may determine that the axial acceleration value has reached or exceeded zero and become negative, and immediately switch to the second setting thereafter. In another example of this form, the controller 122 may fit a mathematical model (e.g., a moving average) to the acceleration data and predict when the acceleration will reach zero. In an example where the controller 122 predicts zero acceleration, the controller 122 may switch to the second setting at a predetermined time before the zero value so that delays in signal processing, momentum, etc. are compensated.

[0061] refer to Figure 8 , an installation process or method 910 is shown. The installation method 910 includes step 914. At step 914, one or more substrates (eg, first substrate 210 and second substrate 214) are positioned. The method 910 then proceeds to step 918.

[0062] At step 918 , the controller 122 positions the driver 114 to engage the FDS 10 and cause the tip 34 of the FDS 10 to contact the first substrate 210 at a predetermined location on the first substrate 210 . The method 910 then proceeds to step 922 .

[0063] The start of step 922 corresponds to line 410 ( Figure 4 ). At step 422, the controller 122 operates the automatic tool 110 in a first setting. For the first setting, the controller 122 controls the driver 114 to rotate at a first rotational speed and apply a first axial force on the FDS 10. In other words, the controller 122 sends a signal to the driver 114 to cause the driver 114 to rotate the FDS 10 at the first rotational speed while pressing the FDS 10 against the first substrate 210 using the first axial feed force.

[0064] Although minor fluctuations may occur, the control signals from the controller 122 for the first setting are configured to operate the drive at a constant rotational speed and axial feed force during step 922 .

[0065] As indicated by step 916, while the driver 114 is applying the first rotational speed and the first axial feed force, the sensor 118 detects the depth or position of the FDS 10. The controller 122 receives a signal from the sensor 118.

[0066] At step 920, the controller 122 calculates acceleration data (e.g., acceleration data 810), as discussed above. In an alternative form not specifically shown, step 916 may include directly detecting the acceleration of the FDS 10 via an accelerometer-type sensor, and step 920 may involve the controller receiving this data and optionally applying a smoothing filter to the directly detected acceleration data.

[0067] Returning to the example provided, at step 926, the controller 122 determines whether a predetermined first trigger condition is met based on the acceleration data from step 920. The first trigger condition of method 910 is a threshold acceleration value of the FDS 10, such as threshold 814 ( Figure 7 ) and / or those thresholds discussed otherwise above.

[0068] The controller 122 continues to operate the drive 114 at the first rotational speed and the first axial feed force until the first trigger condition is met. Detection of the first trigger condition is configured to cause the FDS 10 to trigger on line 422 ( Figure 3 ) to achieve the start of phase 3, and compensate for delays in data processing, signal propagation, and physical momentum of components, as discussed above. When the first trigger condition is met, method 910 immediately and directly proceeds to step 930.

[0069] At step 930, the controller 122 operates the automatic tool 110 in the second setting. In the second setting, the controller 122 sends a signal to the driver 114 to immediately begin operating the driver 114 at the second rotational speed and the second axial feed force.

[0070] Although minor fluctuations may occur, the control signals from the controller 122 for the second setting are configured to operate the drive at a constant rotational speed and axial feed force during step 930 .

[0071] While the driver 114 is applying the second rotational speed and the second axial feed force, the sensor 118 can continue to detect the depth (ie, position) of the FDS 10 . The sensor 118 can also detect the torque value. The controller 122 continues to receive signals from the sensor 118 .

[0072] At step 934, the controller 122 determines whether a predetermined end trigger condition is met based on the signal from the sensor 118. The end trigger condition can be a final torque value. The controller 122 continues to operate the driver 114 at a second rotational speed and a second axial force until the end trigger condition is met. Once the end trigger condition is met, the controller 122 stops the rotation and axial force of the driver 114 to end the method, as indicated by step 938. It should be understood that additional steps can be taken when reaching step 938, and the end of the specific method discussed does not require that the driver 114 and / or the controller 122 must stop operating in all capacities at this time. For example, an industry standard process for torque control can be used to tighten the joint.

[0073] In another form, the devices and methods described herein may also be combined with the teachings of U.S. Application No. 18 / 365,660, filed on August 4, 2023, the entire disclosure of which is incorporated herein by reference. For example, the screw acceleration threshold of the present disclosure may be used as the first trigger condition described in U.S. Application No. 18 / 365,660, rather than the axial velocity (i.e., depth gradient) described therein.

[0074] Thus, the methods and systems described herein compensate for variations in sensors, screw geometry, substrate geometry, and other manufacturing factors such as clearances from part assembly and compliance in assemblies and fixtures.

[0075] Unless otherwise expressly indicated herein, all numerical values ​​indicating mechanical / thermal properties, composition percentages, dimensions and / or tolerances or other characteristics when describing the scope of the present disclosure should be understood to be modified by the word "about" or "approximately". Such modifications are desirable for a variety of reasons, including: industrial practice; material, manufacturing and assembly tolerances; and testing capabilities.

[0076] As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A or B or C), using a non-exclusive logical "or", and should not be construed to mean "at least one of A, at least one of B, and at least one of C."

[0077] In this application, the terms "controller" and / or "module" may refer to, be part of, or include: an application-specific integrated circuit (ASIC); a digital, analog, or mixed analog / digital discrete circuit; a digital, analog, or mixed analog / digital integrated circuit; a combinatorial logic circuit; a field programmable gate array (FPGA); a processor circuit (shared, dedicated, or group) that executes code; a memory circuit (shared, dedicated, or group) that stores code executed by the processor circuit; other suitable hardware components that provide the described functionality (e.g., an operational amplifier circuit integrator as part of a heat flux data module); or a combination of some or all of the above, such as in a system on a chip.

[0078] The term memory is a subset of the term computer-readable medium. The term computer-readable medium as used herein does not encompass transient electrical or electromagnetic signals propagated through a medium (such as on a carrier wave); therefore, the term computer-readable medium may be considered to be tangible and non-transitory. Non-limiting examples of non-transitory tangible computer-readable media are non-volatile memory circuits (such as flash memory circuits, erasable programmable read-only memory circuits, or mask read-only circuits), volatile memory circuits (such as static random access memory circuits or dynamic random access memory circuits), magnetic storage media (such as analog or digital tape or hard drives), and optical storage media (such as CDs, DVDs, or Blu-ray discs).

[0079] The apparatus and methods described in this application may be implemented partially or completely by a special-purpose computer, which is created by configuring a general-purpose computer to perform one or more specific functions embodied in a computer program. The functional blocks, flow chart components, and other elements described above are used as software specifications, which can be translated into a computer program by routine work of a technician or programmer.

[0080] The description of the present disclosure is merely exemplary in nature, and thus, variations that do not depart from the essence of the present disclosure are intended to be within the scope of the present disclosure. Such variations should not be regarded as a departure from the spirit and scope of the present disclosure.

[0081] According to the present invention, a method for installing a flow drill screw (FDS) into a substrate includes: engaging the FDS with an automatic tool; operating the automatic tool with a first setting to drive the FDS into the substrate by causing the substrate to flow to allow the FDS to penetrate the substrate, the first setting being configured to rotate the FDS at a first rotational speed and apply a first axial feed force on the FDS, the first setting being configured to cause the substrate to flow to allow the FDS to penetrate the substrate; detecting position data of the FDS while operating the automatic tool with the first setting; calculating axial acceleration data of the FDS based on the detected position data; and switching the automatic tool from the first setting to a second setting based on a maximum axial acceleration value or the axial acceleration data exceeding a predetermined axial acceleration value, wherein the second setting is configured to rotate the FDS at a second rotational speed and apply a second axial feed force to the FDS, wherein the second rotational speed is less than the first rotational speed.

[0082] According to one embodiment, the above invention is further characterized by applying a smoothing filter to the detected position data to generate a smoothed position data set, wherein the smoothed position data set is used to calculate the axial acceleration data.

[0083] According to one embodiment, the above invention is further characterized by: calculating axial velocity data based on the detected position data; applying a smoothing filter to the calculated axial velocity data to generate a smoothed axial velocity data set, wherein the smoothed axial velocity data set is used to calculate the axial acceleration.

[0084] According to one embodiment, switching the automatic tool from the first setting to the second setting is based on the axial acceleration data exceeding a predetermined axial acceleration value, wherein the predetermined axial acceleration value is between 500 and 50,000 mm / s 2 between.

[0085] According to one embodiment, the above invention is further characterized by positioning one or more additional substrates adjacent to the substrate such that the FDS clamps the one or more additional substrates to the substrate after completing the method.

[0086] According to one embodiment, the first rotational speed is between 1,500 and 12,000 RPM, inclusive; and the first axial feed force is between 0.5 and 4 kN, inclusive; wherein the second rotational speed is between 500 and 4,000 RPM, inclusive; and the second axial feed force is between 0.25 and 1.25 kN, inclusive.

Claims

1. A method of installing a flow drill screw (FDS) into a substrate, the method comprising: engaging the FDS with an automated tool; operating the automatic tool in a first setting configured to rotate the FDS at a first rotational speed and exert a first axial feed force on the FDS to drive the FDS into the substrate by causing the substrate to flow to allow the FDS to penetrate the substrate, the first setting configured to cause the substrate to flow to allow the FDS to penetrate the substrate; as well as The automatic tool is switched from the first setting to a second setting in response to a controller analyzing axial acceleration data of the FDS, wherein the second setting is configured to rotate the FDS at a second rotational speed and apply a second axial feed force to the FDS, wherein the second rotational speed is less than the first rotational speed.

2. The method according to claim 1, further comprising: detecting position data of the FDS while operating the automatic tool in the first setting; as well as The axial acceleration of the FDS is calculated based on the detected position data.

3. The method according to claim 2, further comprising: A smoothing filter is applied to the detected position data to generate a smoothed position data set, wherein the smoothed position data set is used to calculate the axial acceleration.

4. The method according to claim 2, further comprising: Calculate axial velocity data based on the detected position data; A smoothing filter is applied to the calculated axial velocity data to generate a smoothed axial velocity data set, wherein the axial acceleration is calculated using the smoothed axial velocity data set.

5. The method of claim 1 , wherein switching the automatic tool from the first setting to the second setting is performed in response to the controller determining that the axial acceleration of the FDS exceeds a predetermined axial acceleration value, the predetermined axial acceleration value being between 1,000 and 30,000 mm / s 2 between. The method of claim 1 , wherein the axial acceleration data is measured by an accelerometer.

7. The method of claim 1, further comprising positioning one or more additional substrates adjacent to the substrate such that the FDS clamps the one or more additional substrates to the substrate after completion of the method.

8. The method of claim 1, wherein the first rotational speed is between 1,500 and 12,000 RPM, inclusive; and the first axial feed force is between 0.5 and 4 kN, inclusive; wherein the second rotational speed is between 500 and 4,000 RPM, inclusive; and the second axial feed force is between 0.25 and 1.25 kN, inclusive.

9. A system for installing a flow drill screw (FDS), comprising: a driving unit configured to rotate the FDS about an axis at a certain rotational speed while applying an axial feed force on the FDS to drive the FDS through at least one substrate; as well as A controller is configured to change the rotational speed and the axial feed force in response to a measured or calculated axial acceleration of the FDS exceeding a predetermined axial acceleration value.

10. The system of claim 9, further comprising a sensor configured to detect position data of the FDS, Wherein the controller is configured to calculate the axial acceleration of the FDS based on the detected position data of the FDS.

11. The system of claim 10, wherein the controller is configured to apply a smoothing filter to the position data to generate a smoothed position data set, wherein the axial acceleration is calculated using the smoothed position data set.

12. The system of claim 9, wherein the controller is configured to reduce the rotational speed and the axial feed force from a first rotational speed and axial feed force to a second rotational speed and second axial feed force in response to the axial acceleration of the FDS exceeding the predetermined axial acceleration value.

13. The system of claim 12, wherein the first rotational speed is between 1,500 and 12,000 RPM, inclusive; and the first axial feed force is between 0.5 and 4 kN, inclusive; wherein the second rotational speed is between 500 and 4,000 RPM, inclusive; and the second axial feed force is between 0.25 and 1.25 kN, inclusive.

14. The system of claim 9, wherein the predetermined axial acceleration value is between 500 and 3,000 mm / s 2 between.

15. The system of claim 9, further comprising an accelerometer coupled to the drive unit and configured to measure an axial acceleration of the FDS.

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