Head height and material measurement

Abstract

A computer-implemented method of determining attributes of a fastener. The method includes receiving a stored offset factor that correlates an offset of the fastener mounting tool with a peak force applied to the mold by the fastener. The method further includes receiving a determined peak force, the determined peak force corresponding to a peak force applied to the fastener by a punch of the fastener installation tool. The method further includes receiving a determined thickness of the workpiece, receiving a determined location of a top surface of the fastener; and determining a head height of the fastener.

Description

Technical Field

[0001] The present invention relates to a computer-implemented method of determining a property of a fastener and a computer-implemented method of determining a property of a workpiece and / or a fastener installation tool. Background Art

[0002] Fasteners, such as self-piercing rivets, may be inserted into a workpiece to mechanically secure panels of the workpiece together. Self-piercing rivets may also be referred to as self-inserting rivets. The workpiece may include two or more panels. The workpiece may further include an interlayer material, such as an adhesive, a sealant, and / or a foil, disposed between two adjacent panels. As an example, the workpiece may include an aluminum sheet that may form part of an automobile or other vehicle.

[0003] The fastener may be inserted using a fastener installation tool. The fastener installation tool typically punches the fastener into the workpiece while the workpiece is supported by a die. In the example of a self-piercing rivet, the self-piercing rivet may flare in a radially outward manner to enable panels of the workpiece to be secured together. The surface of the die supporting the workpiece may be provided with a shape that facilitates the flaring of the self-piercing rivet.

[0004] Similar workpieces may not be identical. For example, workpieces from a single batch corresponding to a portion of a product may each differ from the nominal workpiece by a different amount. In other words, while the thickness of the nominal workpiece may be known, the thickness of each workpiece may not be known without measuring each workpiece separately. Other properties of the workpiece (e.g., strength or ductility) may also be unknown without measuring each workpiece separately. Measuring each component of each workpiece (i.e., each panel and, optionally, each interlayer material) or measuring each workpiece separately may add additional steps to the build process and, therefore, may slow down the build process.

[0005] A fastener may be inserted into a workpiece at a predetermined speed and force to achieve a desired insertion depth (of the fastener). After insertion into the surface of the workpiece, the head height of the fastener (i.e., the position of the top surface of the fastener relative to the top surface of the workpiece in an area proximate to the fastener) may be indicative of a property of the joint made by the fastener. Without destructive testing, head height may be the only indication of joint strength. Measuring head height in a conventional manner may add one or more additional steps to the build process and may therefore slow down the build process.

[0006] When using an inertia fastener installation tool, the amount of energy available to be provided to the fastener has contributions from the inertia of the flywheel, the linear momentum of the tool, and the torque provided by the motor. The amount of energy available to be provided to the fastener may be reduced due to frictional losses within the tool. The frictional losses may vary depending on the condition of the tool. The condition may include, for example, temperature, life, fastener characteristics, workpiece characteristics, previous use of the tool, lubrication characteristics (such as lubricant amount, lubrication temperature), etc.

[0007] The tool can be in a "cold" state. The tool can be cold when at a temperature below the desired operating temperature. The tool can be cold when no insertion cycles have recently been performed. Being in the cold state may cause the tool to have increased internal friction, for example due to the lubrication being at a sub-optimal temperature (i.e., cold) and / or due to other factors, such as the tool being used with new, worn, or damaged parts / components.

[0008] Alternatively, the tool can be in a "hot" state. The tool can be hot when at the desired operating temperature. The tool can be hot when a sufficient number of insertion cycles have recently (e.g., within the past 15 minutes) been performed. Being in the hot state can cause the tool to have reduced internal friction, for example due to the lubrication being at an optimal temperature (i.e., hot) and / or due to other factors, such as the tool being used with parts / components that are not new, worn, or damaged.

[0009] Alternatively, the tool can be "warming up". A tool that is warming up can be between the "cold" state and the "hot" state, and the operating temperature can increase.

[0010] Compared to a hot tool, a cold tool and / or a tool that is warming up may experience greater internal friction. The increased internal friction may be due to changes in the viscosity of the lubricant and / or the movement and position of the lubricant within the tool, as well as changes in the condition of the internal components. As such, it is beneficial to operate a hot tool as it requires less driving force compared to a cold tool or a tool that is warming up. However, it may be necessary to use a cold or warming up tool, for example because the tool will be cold during initial use. In such cases, compensating for the frictional losses can be beneficial.

[0011] When a tool first rivets a workpiece (or a class of workpieces), the parameters (such as force) used by the tool are typically selected by the engineer operating the tool. For example, the parameters can be selected based on the engineer's experience. The parameters can be input into the tool by using a human-machine interface (HMI). The parameter may not be optimal. For example, some workpieces may require a greater or smaller force (than the force selected by the engineer) to achieve a joint with the desired characteristics. Although an excessive force is used, the joint formed by the tool at the workpiece may still look satisfactory. That is, the die can maintain the expected workpiece volume, the panel gap can be closed, and the fastener head can be flush. However, such a joint may have been formed by using a greater force than necessary. Using an excessive force in this way may reduce the life of the tool and its components. For example, the punch and / or the blank holder may undergo excessive wear due to the use of an excessive force.

[0012] The use of an excessive force is unlikely to be detected by the engineer operating the tool. This may be the case regardless of the installer technology or the method used to apply the force (i.e., whether a hydraulic, electric, or electro-hydraulic system is used). This is because once the die is filled and the fastener head height is flush, a greater force can be applied without changing the final head height. In other words, the head height of the fastener after the tool has applied the optimal amount of force can be the same as the head height of the fastener after the tool has applied an excessive amount of force. Although force has been discussed as an example of a parameter, similar considerations apply to other examples, such as the energy applied by the tool or the speed at which the tool operates.

[0013] An object of the present invention is to overcome or mitigate one or more of these problems. Summary of the Invention

[0014] In a first example described herein, there is a computer-implemented method for determining an attribute of a fastener, the method comprising: receiving a stored deflection factor that correlates the deflection of a fastener installation tool with the peak force applied by the fastener to a die; receiving a determined peak force that corresponds to the peak force applied by a punch of the fastener installation tool to the fastener; receiving a determined thickness of the workpiece; receiving a determined position of the top surface of the fastener; and determining the head height of the fastener, i.e., HH, as:

[0015] HH = (DF × PF) - MT + ED

[0016] where: DF is the stored deflection factor; PF is the determined peak force; MT is the determined thickness of the workpiece; and ED is the determined position of the top surface of the fastener.

[0017] Advantageously, the method can allow determination of the head height of a fastener without measuring the head height itself. The head height of the fastener can represent an attribute of the workpiece. The head height can also be referred to as the position of the top surface of the head of the fastener relative to the top surface of the workpiece in the region near the fastener. The region near the fastener can be the region immediately surrounding the fastener, or can be a region beyond the region deformed due to the insertion of the fastener.

[0018] As an alternative to (or in addition to) a destructive test, the determined head height of the fastener can provide an indication of the strength (or another attribute) of the joint (i.e., the joint made by the fastener). For example, the head height of a first joint in a first workpiece can be determined, and a destructive test can be used to determine the strength of the first joint. The head height of a second joint in a second workpiece can be determined, and its strength can be inferred based on the head height and strength of the first joint.

[0019] The fastener can be a rivet (e.g., a self-piercing rivet). The blank holder can also be referred to as a workpiece holder or a nose. The die can be configured to prevent the workpiece from moving under the force applied to the workpiece. The die can also be referred to as an anvil.

[0020] The position of the top surface of the fastener can be measured using a first sensor, measured using a second sensor, or determined using an encoder. For example, the velocity of the punch as a function of time can be recorded and used to determine the maximum displacement of the punch, and the determined maximum displacement of the punch can be used to determine the position of the top surface of the fastener.

[0021] Determining the peak force applied by the punch to the fastener can include using a force sensor, such as a force sensor disposed on the punch. Alternatively, the force can be determined by measuring the motor torque applied to the punch using an encoder.

[0022] The top surface of the fastener can be the surface of the fastener that is opposite to and / or in contact with the punch. When the blank holder is in the retracted position, the top surface of the fastener can be the face of the fastener closest to the blank holder.

[0023] The offset of the fastener installation tool can be the die being offset from a first position to a second position due to the force applied by the fastener installation tool. The offset factor can be related to the position of the fastener at the workpiece and / or similar workpieces. In other words, if the fastener is inserted at different positions of the workpiece, different offset factors can be received. If the fastener is inserted at similar positions of similar workpieces, the same offset factor can be received. Alternatively, the offset factor can be consistent at the workpiece and / or similar workpieces.

[0024] The determined thickness of the received workpiece may further include: advancing the blank holder of the fastener installation tool such that the blank holder moves to a calibration position; using a first sensor configured to measure the displacement of the blank holder to measure the position of the calibration position along the axis traveled by the blank holder; advancing the blank holder such that the blank holder contacts the surface of the workpiece and clamps the workpiece against the mold; using the first sensor to measure the position of the surface of the workpiece along the axis traveled by the blank holder; and using the measured position of the calibration position and the measured position of the surface of the workpiece to determine the thickness of the workpiece.

[0025] Advantageously, using the calibration position can improve the accuracy of the measurement.

[0026] The calibration position may be the position of the blank holder when the blank holder has contacted the surface of the mold. In other words, the calibration position may be the first position of the mold and / or the measured position of the calibration position may be the first measured position of the surface of the mold. Alternatively, the calibration position may be the position of the blank holder when the blank holder has contacted the surface of a calibration member placed on the mold. For example, the calibration member may be a nominal workpiece and / or have the same width as the expected width of the workpiece.

[0027] The method may further include retracting the blank holder such that the workpiece can be inserted between the blank holder and the mold.

[0028] Once the blank holder has contacted the surface of the workpiece, the blank holder can clamp the workpiece against the mold.

[0029] The measured position of the calibration position may be expressed as the distance traveled by the blank holder to move the blank holder to the calibration position. Similarly, the measured position of the workpiece surface may be expressed as the distance traveled by the blank holder to cause the blank holder to contact the workpiece surface.

[0030] The determined thickness of the workpiece may be determined relative to the calibration position. In an example where the calibration position is the first position of the mold, the determined thickness of the workpiece may be the thickness of the workpiece (i.e., the absolute thickness). For example, the workpiece may be determined to be 5.6 mm thick. In an example where the calibration position is the position of the blank holder when the blank holder contacts the surface of the calibration member, the determined thickness of the workpiece may be determined relative to the thickness of the calibration member (i.e., the relative thickness). For example, the determined thickness may be 1 mm thicker than the thickness of the calibration member.

[0031] The determined position of the top surface of the fastener may be determined relative to the calibration position. In an example where the calibration position is the surface of the mold, the determined position of the top surface of the fastener may be determined relative to the measured position of the surface of the mold.

[0032] The method may further include receiving the thickness of the calibration member and determining the absolute thickness of the workpiece based on the determined thickness of the workpiece relative to the thickness of the calibration member. In other words, the absolute thickness may be determined based on the relative thickness. For example, the determined thickness relative to the calibration member may be 1 mm thick (i.e., 1 mm thicker than the calibration member), and the thickness of the calibration member of 4.6 mm may be received, and the absolute thickness of the workpiece may be determined to be 5.6 mm.

[0033] The method may further include applying a threshold test to the determined head height.

[0034] A binary result may be provided from the threshold test. For example, the threshold test may be 5 mm (or less), the determined head height may be 5.6 mm, and the threshold test may provide a result of 0 to indicate that the threshold test has failed. Alternatively, for a determined head height of 4.6 mm, the same threshold test may provide a result of 1 to indicate that the threshold test has passed. As an alternative, the threshold test may test whether the determined head height is greater than, greater than or equal to, or less than or equal to the threshold. The result of the threshold test may be represented as a warning indicator and / or a fault indicator.

[0035] The method may include applying one threshold test or multiple threshold tests to the determined head height. In other words, the threshold test may be one of multiple threshold tests. Each test may correspond to a respective condition.

[0036] In a second example described herein, there is a method of determining properties of a workpiece and / or a fastener installation tool implemented by a computer, the method including: advancing a blank holder of the fastener installation tool such that the blank holder moves to a calibration position; measuring the position of the calibration position along an axis traveled by the blank holder using a first sensor configured to measure displacement of the blank holder; advancing the blank holder such that the blank holder contacts a surface of the workpiece and clamps the workpiece against a die; measuring the position of the surface of the workpiece using the first sensor; and determining the thickness of the workpiece using the measured position of the calibration position and the measured position of the surface of the workpiece.

[0037] The properties of the workpiece may include properties of a joint made at the workpiece.

[0038] Similar to the first example, the method may further include applying a threshold test to the determined thickness of the workpiece. The method may further include determining that the fastener installation tool needs maintenance based on the result of the threshold test; determining that the workpiece should be inspected and / or replaced based on the result of the threshold test; and / or determining that a parameter associated with the fastener installation tool should be adjusted based on the result of the threshold test.

[0039] The method may further include retracting the blank holder so that the workpiece can be inserted between the blank holder and the die.

[0040] The method may further include: receiving the determined position of the top surface of the fastener; receiving the measured head height of the fastener; determining a tool offset TD (which corresponds to the change in the end position of a component of the tool relative to the starting position due to the insertion of the fastener) as:

[0041] TD = HH + MT - ED

[0042] where: HH is the measured head height of the fastener; MT is the determined thickness of the workpiece; and ED is the determined position of the top surface of the fastener.

[0043] The measured head height can be manually measured, for example, by an operator of the fastener installation tool using a dial test indicator. The fastener can be a fastener inserted into the workpiece.

[0044] The method may further include storing the determined tool offset. For example, the tool offset can be stored in a computer-readable memory.

[0045] The method may further include: determining the peak force applied by the punch to the fastener; and determining an offset factor, i.e., DF (which corresponds to the offset of the fastener installation tool relative to the peak force applied by the punch to the fastener) as:

[0046] DF = TD ÷ PF

[0047] where PF is the determined peak force.

[0048] Advantageously, the offset factor can allow the determination of the head height of the fastener without measuring the head height itself.

[0049] The offset factor and / or the tool offset can depend on the position of the joint (i.e., the joint made by the fastener at the workpiece). In other words, the offset factor and / or the tool offset can be determined for the position of the joint. If the properties of the joint change (e.g., the position, the workpiece, or the fastener changes), then a new offset factor and / or tool offset can be determined. The position of the joint can be applied to a single workpiece or multiple workpieces having joints at corresponding positions.

[0050] The method may further include storing the offset factor. For example, the offset factor can be stored in a computer-readable memory.

[0051] The method may further include applying a threshold test to the determined property. For example, the threshold test can be applied to the offset factor, the tool offset, and the workpiece thickness.

[0052] In a third example described herein, there is a computer-implemented method for determining a property of a workpiece or a joint made at the workpiece, the method comprising: contacting a blank holder of a fastener installation tool with a surface of the workpiece; applying a force along an axis of the blank holder towards the workpiece to the blank holder; detecting movement of the workpiece by measuring displacement of the blank holder; and determining a property of the workpiece or a joint made at the workpiece based on the detected movement.

[0053] The method may further comprise determining that a predetermined feature is present in the detected movement. The predetermined feature may include, for example, a consistent movement of a panel of the workpiece in a single direction. In other words, two or more panels of the workpiece may gradually move together under the force applied by the blank holder, i.e., two or more panels may be squeezed together. The predetermined feature may include, for example, oscillation of one or more panels. In other words, one or more panels may move back and forth in response to a perturbation provided by the force applied through the blank holder.

[0054] Movement of the workpiece may be in response to the force applied by the blank holder. Additionally or alternatively, movement of the workpiece may be in response to a fastener inserted through a punch of the fastener installation tool.

[0055] Detection that two or more panels are squeezed together may indicate that a panel gap existed in the workpiece prior to being squeezed together. Additionally or alternatively, detection that two or more panels are squeezed together may indicate the presence and / or amount of adhesive present.

[0056] Detection of oscillation may indicate brittleness of a panel of the workpiece.

[0057] The property of the workpiece may be a property of a panel of the workpiece (e.g., the topmost panel). In other words, the property may be a property of the panel closest to the blank holder.

[0058] The method may further comprise applying a threshold test to the determined property.

[0059] Any method may further comprise inserting a fastener into the workpiece by a punch of the fastener installation tool. In other words, the fastener may form a joint at the workpiece. The fastener may be a first fastener. It should be understood that the insertion may be successful or unsuccessful. Further, the fastener may be fully inserted or partially inserted after insertion.

[0060] The property may be deformation of the workpiece (or a panel at the workpiece).

[0061] Any method may further comprise determining that the fastener installation tool needs maintenance based on the result of the threshold test.

[0062] Any method may further include indicating to the user that maintenance is required and / or the method may further include performing maintenance. The method may further include determining, based on the results of a threshold test, that the fastener installation tool does not require maintenance.

[0063] In an example where the method includes multiple threshold tests, determining that the fastener installation tool requires maintenance and / or determining that the fastener installation tool does not require maintenance may be based on the results of one or more of the multiple threshold tests. The method may further include providing an indication that maintenance is required, scheduling maintenance, and / or causing maintenance to be performed.

[0064] Any method may further include determining, based on the results of a threshold test, that a workpiece should be replaced.

[0065] In other words, the method may identify that the workpiece is not suitable for use in a process and / or product. For example, for the intended use of the workpiece, the workpiece may be too brittle, too ductile, too thick, too thin, and / or too hard. The method may further include providing an indication that the workpiece should be replaced and / or replacing the workpiece.

[0066] Any method may further include determining, based on the results of a threshold test, that a parameter associated with the fastener installation tool should be adjusted.

[0067] In other words, the method may identify that the joint (i.e., the joint made by the fastener in the workpiece) can be improved by changing a parameter associated with the fastener installation tool. For example, the force applied by the punch to the fastener and / or the speed of the punch may be adjusted. The method may further include providing an indication that the parameter should be adjusted and / or causing the parameter to be adjusted. The parameter may be adjusted such that the fastener installation tool inserts the fastener using the adjusted parameter (i.e., continues / completes the insertion of the fastener). Additionally or alternatively, the parameter may be adjusted such that the fastener installation tool inserts subsequent fasteners into the same workpiece and / or subsequent workpieces using the adjusted parameter. As an example of a parameter that may be adjusted, the type of rivet inserted may be changed.

[0068] Measuring the displacement of the blank holder can include measuring the displacement of a member of the fastener installation tool that is fixed relative to the blank holder. Such a method allows for measuring the displacement of the blank holder without directly measuring the position of the blank holder. Accordingly, sensors do not need to be provided in an area close to the blank holder. Advantageously, measuring the position of the blank holder relative to a calibration position can reduce the length of the member required to measure the displacement of the blank holder. Beneficially, this can also reduce the space occupied by the blank holder, thereby improving access to the workpiece in an industrial production installation. Beneficially, by not requiring sensors to be provided in an area close to the blank holder, the sensors can be located further away from areas more exposed to debris, dust, and / or damage, and thus the potential lifespan of the sensors is increased and the need for repairs is reduced. For example, measuring the position of the calibration position can include measuring a first position of the member (i.e., the position of the member when the blank holder is in the calibration position). As another example, measuring the position of the surface of the workpiece can include measuring a second position of the member (i.e., the position of the member when the blank holder contacts the surface of the workpiece).

[0069] The method according to any of the foregoing examples can further include comparing a determined attribute with a predetermined attribute, wherein the difference between the determined attribute and the predetermined attribute represents the condition of the fastener installation tool or the workpiece; calculating an adjustment based on the comparison to compensate for the condition of the fastener installation tool or the workpiece; and applying the adjustment to the fastener installation tool and / or the workpiece.

[0070] The performance of the fastener installation tool can vary depending on the condition of the tool, such as whether the tool is cold, warming up, or hot. By employing this method, the varying performance of the tool can be compensated for. In particular, the effect of frictional losses can be indirectly determined by measuring a first parameter and comparing it with a predetermined parameter. Accordingly, calculating and applying an adjustment thereto provides a method of compensation. Such a method of compensation can beneficially improve the performance of the tool.

[0071] The energy consumption and / or wear rate of the fastener installation tool can vary depending on the condition of the tool, e.g., depending on target parameters set for the tool. Exemplary target parameters can include force and / or energy. As described above, once sufficient force is applied to the tool such that the die is filled, applying additional (i.e., excessive) force may not change the head height. By using this method, the optimal head height can be achieved with minimum force and / or minimum energy consumption. Such a method of compensation can beneficially save energy and increase the lifespan of the tool and its components.

[0072] The determined attribute can be, for example, the determined head height of a first fastener. As an alternative example, the attribute can be an offset factor.

[0073] Predetermined attributes can be determined at any earlier point in time. For example, the predetermined attributes can be loaded from a database. As an alternative example, the predetermined attributes can be determined based on the insertion of a previous fastener.

[0074] The condition of the fastener installation tool can be or include temperature, life, previous use of the tool, lubrication characteristics (such as lubrication amount, temperature of lubrication), etc. The condition of the workpiece can be or include the strength, ductility, or properties of the fastener.

[0075] Method 800 can be iteratively executed to form a feedback loop. For the same or consecutive fasteners, the steps of comparing, calculating, and applying adjustments can be repeated any number of times. In this way, the method can converge to parameters for inserting the fastener to help minimize tool wear while ensuring that the fastener is inserted according to the predetermined attributes.

[0076] In some examples, the adjustment can be automatically applied. That is, the fastener installation tool can apply the adjustment without any further input. In other examples, the method can further include outputting an indication of the adjustment at an output device of the fastener installation tool. The method can further include receiving a user input at an input of the fastener installation tool indicating that the fastener installation tool applies the adjustment, and applying the adjustment in response to the user input.

[0077] Determining the attribute can be based on multiple measurements. For example, determining the attribute can be the average of the determined head heights, each determined head height corresponding to a different fastener.

[0078] Comparing the determined attribute with the predetermined attribute, calculating the adjustment based on the comparison, and applying the adjustment can be performed respectively after the punch has inserted the first fastener into the workpiece. The method can further include, after applying the adjustment, inserting a second fastener into the workpiece with the punch. In other words, the fastener installation tool can insert a first fastener with a first set of parameters, and based on the comparison, can insert a second fastener with a second set of parameters. Additionally or alternatively, the method can further include, after applying the adjustment, further inserting the first fastener into the workpiece with the punch. In other words, the fastener installation tool can insert a first fastener with a first set of parameters, and based on the comparison, can further insert the first fastener with a second set of parameters. In other words, the adjustment can be applied when inserting the first fastener.

[0079] The adjustment can be an adjustment to the torque and / or force applied by the fastener installation tool. For example, the head height of the first fastener can be greater than the required head height. In response, when further inserting the first fastener and / or inserting the second fastener, the fastener installation tool can apply a greater torque and / or force. Alternatively, the head height of the first fastener can be less than the required head height. In response, when inserting the second fastener, the fastener installation tool can apply a smaller torque and / or force. The torque of the motor can correspond to the motor speed or the electrical stimulation provided to the motor.

[0080] The adjustment can be an adjustment to the speed of the fastener installation tool. For example, the speed can be the target speed of the punch operation of the fastener installation tool. Thus, the fastener insertion tool can insert the fastener at an optimal speed. The optimal rate can be the fastest rate that results in the fastener being correctly inserted (i.e., without any over-insertion). Advantageously, such an adjustment can allow for an acceleration of the manufacturing process.

[0081] In some examples, the punch of the fastener installation tool can be configured to operate at a first rate when in a first region and at a second rate when in a second region. In particular, the punch can operate at a higher rate when in the first region that is further away from the fastener to be inserted and at a lower rate when in the second region that is closer to the fastener. In other words, the punch can operate at a flying-through-space rate. In such examples, the adjustment can be directed at the first rate and / or the second rate.

[0082] The method according to any one of the preceding examples can further include comparing a determined property with a predetermined property, wherein the difference between the determined property and the predetermined property can indicate the condition of the fastener installation tool and / or the workpiece; and determining, based on the comparison, that no adjustment to the fastener installation tool and / or the workpiece is required.

[0083] The determined property can be the determined head height of the first fastener; and the predetermined property can be the predetermined head height.

[0084] The determined property can be the determined thickness of the workpiece; and the predetermined property can be the predetermined thickness.

[0085] The determined property can be the determined tool offset; and the predetermined property can be the predetermined tool offset.

[0086] The determined property can be the determined offset factor; and the predetermined property is the predetermined offset factor.

[0087] In a fourth example described herein, there is a computer-implemented method for determining a force for inserting a fastener into a workpiece using a fastener installation tool, the method comprising: receiving a desired head height of the fastener; receiving a thickness of the workpiece; receiving an offset factor; receiving a desired position of a top surface of the fastener; and determining a force PF applied to the fastener by a punch of the fastener installation tool as:

[0088]

[0089] where: HH is the desired head height of the fastener; DF is the offset factor; MT is the thickness of the workpiece; and ED is the position of the top surface of the fastener.

[0090] The method may further comprise using the fastener installation tool to insert the fastener into the workpiece with the determined force.

[0091] In a fifth example described herein, there is a fastener installation tool configured for use in the method according to any one of the preceding examples.

[0092] In a sixth example described herein, there is a controller for a fastener installation tool, wherein the controller is configured to perform the method according to any one of the first to fifth examples.

[0093] In a seventh example described herein, there is a fastener installation tool comprising a first sensor configured to measure a displacement of a blank holder.

[0094] The fastener installation tool may further comprise a member fixed relative to the blank holder. The first sensor may be configured to measure a displacement of the member.

[0095] The first sensor may be a contact displacement sensor.

[0096] It should be understood that a reference to any of the following: receiving a quantity; determining a quantity; and measuring a quantity may be interpreted similarly. For example, receiving a determined position of the top surface of the fastener may include determining and / or measuring the position of the top surface of the fastener.

[0097] It should also be understood that the steps of any method may be carried out in any suitable order. For example, in the method of the first example, the position of the surface of the workpiece may be received before receiving the position of the calibration position. BRIEF DESCRIPTION OF THE DRAWINGS

[0098] Embodiments of the present invention will now be described, by way of example only, with reference to the following drawings, in which:

[0099] Figure 1 is a side view of an exemplary rivet installation tool;

[0100] Figure 2 is a flowchart depicting a method for determining the thickness of a workpiece;

[0101] Figure 3A - Figure 3F schematically shows a system including a rivet installation tool during a method for determining the thickness of a workpiece;

[0102] Figure 4 is a flowchart depicting a method for determining tool offset;

[0103] Figure 5 is a flowchart depicting a method for determining the head height of a fastener;

[0104] Figure 6 is a flowchart depicting a method for determining the force for inserting a fastener;

[0105] Figure 7 is a flowchart depicting a method for determining the properties of a workpiece or a joint made in a workpiece;

[0106] Figure 8 is a flowchart depicting a method for calculating an adjustment and applying the adjustment to a fastener installation tool and / or a workpiece;

[0107] Figure 9 is a flowchart depicting a method for determining that no adjustment to a fastener installation tool and / or a workpiece is required;

[0108] Figure 10 is a flowchart depicting an iterative method for calculating an adjustment and applying the adjustment to a fastener installation tool and / or a workpiece; and

[0109] Figure 11 depicts an exemplary computer system that can be used to perform the methods described herein. Detailed Description

[0110] Figure 1The rivet insertion tool 2 is depicted in a side view. The rivet insertion tool 2 (which may also be referred to as a fastener installation tool or a rivet installation tool) is mounted on the upper arm of a conventional C-frame 4. A die 6 is mounted on the lower arm of the C-frame 4 using associated mounting components (such as a die holder). The die 6 may also be referred to as an anvil. The workpiece W into which the self-piercing rivet is to be inserted is positioned between the blank holder 14 and the die 6. The rivet installation tool 2 includes an electric motor 8 which is connected via a transmission 10 to an actuator 12 (both of which are located in respective housings). The rivet installation tool 2 further includes a blank holder 14 fixed to the end of the actuator 12. The blank holder 14 may also be referred to as a nose. A portion of the blank holder 14 is a hollow cylinder which allows a punch (not depicted) to extend out of the blank holder 14 to insert the self-piercing rivet into the workpiece W. The self-piercing rivets may be provided on a self-piercing rivet strip which is fed into a portion of the rivet installation tool 2. Alternative devices for providing the self-piercing rivets may be provided. For example, a single rivet feeding system may use a pneumatic system to convey the self-piercing rivets from a hopper.

[0111] The workpiece W may include a plurality of panels. The panels may be, for example, aluminum (such as cast aluminum or extruded aluminum), steel (such as high-strength steel), or magnesium. The devices (such as the rivet insertion tool 2) and methods described herein may be particularly beneficial for use with materials having poor tolerances, such as cast aluminum or extruded aluminum. The panels may form part of an automobile or another vehicle.

[0112] The workpiece W may optionally further include an interlayer material (such as an adhesive, a sealant, and / or a foil). For example, an adhesive layer may be provided between two adjacent panels to provide an additional means of fixing the two adjacent panels together.

[0113] The rivet insertion tool 2 may be provided with a blank holder displacement sensor. The blank holder displacement sensor may also be referred to as a device for measuring the displacement of the blank holder 14. For example, the blank holder displacement sensor may be a sensor for measuring the distance traveled by the blank holder 14. The displacement of the blank holder 14 may be measured relative to a point on the rivet insertion tool 2 that is expected not to move when the rivet is inserted (i.e., a fixed point). The fixed point may be, for example, a point on the actuator 12 or a point on the C-frame 4. The blank holder displacement sensor may be any suitable sensor for measuring the displacement of the blank holder 14. The blank holder displacement sensor may include, for example, a contact displacement sensor 20 (as Figure 1 shown). The blank holder displacement sensor may include a light source and a light sensor, an accelerometer, an inductive sensor, an optical sensor, and / or any other sensor known in the art.

[0114] In an example where the blank holder displacement sensor includes the contact displacement sensor 20, the contact displacement sensor 20 may include a plunger 22 and a sensor body 24. The plunger 22 may be rigid. In the initial position, the plunger 22 may protrude from the sensor body 24. Alternatively, the plunger 22 may be disposed within the sensor body 24 while the surface of the end of the plunger 22 is flush with the surface of the sensor body 24. The plunger 22 may be integral with the dust cover of the contact displacement sensor 20. The contact displacement sensor 20 may be provided with a biasing member to return the plunger 22 to the initial position after the plunger 22 has been displaced. The sensor body 24 may include one or more sensors to determine the displacement of the plunger 22 from the initial position. For example, the plunger 22 may be pushed inward (i.e., more of the plunger 22 is within the sensor body 24 and / or the surface of the end of the plunger 22 is within the sensor body 24 compared to when in the initial position), and the displacement of the plunger 22 may be measured by one or more sensors. When the plunger 22 is no longer being pushed inward, the biasing member may return the plunger 22 to the initial position. The sensor body 24 of the contact displacement sensor 20 may be fixed relative to the blank holder 14. The surface of the plunger 22 configured to contact the object measured by the contact displacement sensor 20 may be referred to as the contact surface. The plunger 22 may be axially aligned with the movement of the blank holder 14. Additional components may be provided to fix the sensor body 24 relative to the blank holder 14 such that the sensor body 24 is not directly fixed to the blank holder 14 (but the sensor body 24 and the blank holder 14 are fixed relative to each other). The rivet insertion tool 2 may be provided with a member 30 fixed relative to a fixed point. The member 30 may be rigid and have a collision surface. For example, the member 30 may be a rod. The member 30 may be rigid. For example, the member 30 may be fixed relative to the actuator 12. The member 30 may be axially aligned with the movement of the blank holder 14 and positioned to contact the end of the plunger 22 (i.e., the contact surface of the contact displacement sensor). In other words, the end face of the plunger 22 may contact the collision surface of the member 30, thereby allowing the contact displacement sensor 20 to measure the displacement of the member 30.

[0115] The contact displacement sensor 20 and the member 30 may allow for an indirect measurement of the position of the blank holder 14. In other words, by measuring the displacement of the contact displacement sensor 20 relative to the member 30, the displacement of the blank holder 14 can be inferred. For example, by measuring the first position of the contact displacement sensor 20 relative to the member 30 when the blank holder 14 is in the first position and the second position of the contact displacement sensor 20 relative to the member 30 when the blank holder 14 is in the second position, the distance between the first position and the second position of the blank holder 14 can be determined.

[0116] Although the sensor body 24 has been described as being fixed relative to the blank holder 14 and the member 30 has been described as being fixed to the actuator 12, the rivet insertion tool 2 (and its components) can be arranged in any suitable manner. For example, in an alternative arrangement, the contact displacement sensor 20 can be fixed to the actuator 12 and the member 30 can be fixed relative to the blank holder 14. Other arrangements capable of measuring the position of the blank holder 14 will be apparent to those skilled in the art.

[0117] As described above, the blank holder displacement sensor can include an inductive sensor. For example, the plunger 22 can include a magnet. The sensor body 24 can include a sensing coil and a generating coil. The coils can be arranged coaxially and one within the other. The sensing coil can measure the magnetic field generated by the flow of charge through the generating coil. The presence of the magnet within the sensing coil and / or generating coil can change the impedance and thus the measured magnetic field. Accordingly, by measuring the magnetic field, the displacement of the magnet can be measured by the blank holder displacement sensor.

[0118] Also as described above, the blank holder displacement sensor can include an optical sensor. For example, the plunger 22 can include a scale. The sensor body 24 can include an optical sensor. The optical sensor can be a CMOS sensor. The blank holder displacement sensor can be configured to determine the displacement of the plunger based on data from the optical sensor. The scale can be linear. Alternatively, the scale can be non-linear. For example, the scale can include a complex pattern that allows for a more accurate measurement of the displacement of the plunger. A portion of the scale can be at least partially translucent. For example, the indication of the scale can be provided on a glass portion. A light source can also be provided within the blank holder displacement sensor. For example, when used in conjunction with at least a partially transparent scale, the light source can be provided on the side of the scale opposite the optical sensor. In this way, the portion of the scale facing the optical sensor can be determined by the contact displacement sensor 20, thereby allowing the displacement of the plunger 22 to be measured.

[0119] As described above, the blank holder displacement sensor may include a light source and a light sensor. The light source may be, for example, a laser. The light source may be fixed at a fixed point, and the blank holder 14 may be provided with the light source. Alternatively, the light source and the light sensor may be fixed at a fixed point, and the blank holder 14 may be provided with a portion for reflecting light. In other words, a portion of the blank holder 14 may be provided with one or more reflecting surfaces (e.g., mirrors and / or prisms). The light sensor or the reflecting surface may be provided on a protrusion extending from the blank holder 14. For example, the light sensor or the reflecting surface may be fixed relative to the blank holder 14 such that the light sensor or the reflecting surface moves as the blank holder 14 moves. The light source, the light sensor, and the reflecting surface may be arranged such that light (emitted by the light source) is detected by the light sensor regardless of the position of the blank holder 14. For example, the light source may emit laser light in a direction parallel to the movement axis of the blank holder. In an example where the blank holder 14 is provided with a light sensor, the light sensor may detect the laser light regardless of the position of the blank holder 14. In an example where the blank holder is provided with a reflecting surface, two reflecting surfaces may reflect the laser light such that the laser light advances toward the light sensor in a direction parallel to the movement axis of the blank holder 14 (regardless of the position of the blank holder 14). By using, for example, timing measurements (timing the time difference between the laser pulse emitted by the light source and the laser pulse detected by the light sensor), the displacement of the blank holder 14 can be inferred. In an example including a reflecting surface, inferring the displacement of the blank holder 14 may require knowledge of the arrangement (e.g., the distance between the two reflecting surfaces and / or the speed of light in the prism).

[0120] Also as described above, the blank holder displacement sensor may include an accelerometer. For example, the accelerometer may measure the acceleration of the blank holder 14, and the measured acceleration may be used to determine the displacement of the blank holder 14.

[0121] Although many exemplary embodiments have been provided above, it should be understood that the measurement of the displacement of the blank holder 14 can be accomplished in any manner.

[0122] The rivet insertion tool 2 can be provided with a punch displacement sensor. The punch displacement sensor can also be referred to as a device for measuring the displacement of the punch. The punch displacement sensor can be, for example, a position sensor, an accelerometer, and / or an encoder. For example, the encoder can allow the measurement of the motor 8 and / or the actuator 12 to determine the displacement of the punch. As an example, the encoder can measure the change in the speed of the motor 8 and / or the actuator 12 over time to allow the determination of the displacement of the punch. As an alternative example, the torque provided by the motor 8 and / or the actuator 12 can be measured, and the measured torque can be used to determine the displacement of the punch. As a further example of the punch displacement sensor, a portion of the blank holder 14 can be a notch. In other words, the slit can extend axially along the blank holder 14. The punch can be provided with a protrusion that extends from the notch of the blank holder 14. The protrusion can allow the displacement of the punch to be measured in a similar manner as described above by using a contact displacement sensor (and optional components such as a rod) or a light source and a light sensor. In other words, the contact displacement sensor (for measuring the displacement of the punch) can contact the protrusion (or a component fixed relative to the protrusion), and can allow the measurement of the displacement of the punch relative to a fixed position (i.e., the position of the contact displacement sensor). Alternatively, the light source can be provided at a fixed position, and the protrusion can be provided with a light sensor. The light sensor can allow the measurement of the displacement of the punch relative to a fixed position.

[0123] The rivet insertion tool 2 can be provided with a force sensor (referred to as a force sensor) for measuring the force applied by the punch to the fastener. The force sensor can also be referred to as a device for measuring the force applied by the punch to the fastener. The force sensor can, for example, be provided together with the punch, and can include, for example, a load sensor and / or a calibrated strain gauge. As an alternative example, the force sensor can include an encoder that can allow the measurement of the position of the motor 8 and / or the actuator 12, which can be correlated with time to determine the acceleration of the tool. The position measurement and mass of the rivet insertion tool 2 can be used to calculate the force applied by the punch to the fastener. As an alternative example, a value can be calculated based on a model of the rivet insertion tool 2. The model can measure the current applied to the motor to determine the torque of the motor 8, the inertia of the actuator 12, and / or the deceleration. The model can be calibrated to correct for effects caused by, for example, temperature changes.

[0124] Although various components of the rivet insertion tool 2 have been described above, it should be understood that the rivet insertion tool 2 is merely an example, and any suitable rivet insertion tool can be used. In other words, the methods disclosed herein can be performed with other rivet insertion tools. For example, various delivery systems (such as a blow-feed system) can be used to deliver the fastener to the rivet insertion tool.

[0125] Figure 2Is a flowchart depicting a method 200 for determining the thickness of a workpiece. In step 201, the blank holder of the fastener installation tool advances to a calibration position. In step 202, the position of the calibration position is measured. In step 203, the blank holder advances to contact the surface of the workpiece. In step 204, the position of the surface of the workpiece is measured. In step 205, the thickness of the workpiece is determined. In optional step 206, a fastener is inserted into the workpiece. In optional step 207, the blank holder 314 and / or the punch 312 may be retracted.

[0126] Figure 3A - Figure 3F (i.e., Figure 3A , Figure 3B , Figure 3C , Figure 3D , Figure 3E and Figure 3F collectively) schematically shows a system 300 including a fastener installation tool 310 during the method 200 for determining the thickness of a workpiece. Figure 3A - Figure 3F Will be used to describe in more detail the actions caused by method 200 (and other methods described below, such as method 400 and method 500). Although different reference numerals are used in Figure 3A - Figure 3F than in Figure 1 , it should be understood that method 200 can be performed on the fastener installation tool 2 shown in Figure 2 .

[0127] Figure 3A Depicts a system 300 including a fastener installation tool 310. The fastener installation tool 310 includes a blank holder 314 and a punch 312 (the punch 312 is not shown in Figure 2 ). At a position below the punch 312, the fastener 320 is held within the blank holder 314. Although the fastener 320 (in Figure 3A ) is depicted as being in a position inside the blank holder 314 and below the punch 312, this is not necessary and the fastener 320 can be moved to such a position later. The fastener 320 can be a rivet (e.g., a self-piercing rivet). The system 300 further includes a die 306. The initial position of the upper surface of the die 306 is represented by a reference line 340. The blank holder 314 and the punch 312 are in a retracted position. In other words, there is a space between the end of the blank holder 314 configured to contact the workpiece and the die 306. The fastener installation tool 310 includes a blank holder displacement sensor. The blank holder displacement sensor is not depicted and can be, for example, any of the examples above (i.e., the blank holder displacement sensor can include a contact displacement sensor, a light source and a light source sensor, and / or an accelerometer). The fastener installation tool 310 can further include a punch displacement sensor and / or a force sensor (for measuring the force applied by the punch 312 to the fastener 320).

[0128] Referring again to Figure 2 , in step 201, the blank holder 314 advances to a calibration position. The calibration position can be the position of the blank holder 314 when the blank holder 314 contacts the surface of the die 306. In other words, the blank holder 314 can touch the surface of the die 306 that can position the workpiece. The blank holder 314 can reach the reference line 340. The blank holder 314 can advance relatively slowly and / or with a relatively low force (i.e., slower or with a smaller force compared to the typical operation of the blank holder 314 as described in step 203) so that neither the blank holder 314 nor the die 306 (or any other component) is deformed due to the force applied to the blank holder 314 or the force applied by the blank holder 314.

[0129] As an alternative, the calibration position can be the position of the blank holder 314 when the blank holder 314 has contacted the surface of a calibration member that has been placed on the die 306. For example, the calibration member can be a nominal workpiece (i.e., a workpiece that has been determined to have nominal dimensions). In other words, the calibration member can have the same thickness as the expected thickness of the workpiece.

[0130] As a further alternative, the calibration position can be the position of the blank holder 314 when the blank holder 314 (or a part of the blank holder 314) has been aligned with an alignment mark provided on the fastener installation tool 310 (such as a C-frame). For example, a first visible tab can be provided on the blank holder 314, a second visible tab can be provided on a part of the C-frame, and the calibration position can be the position of the blank holder 314 when the first visible tab is aligned with the second visible tab.

[0131] Figure 3B Illustrated is the system 300 after the blank holder 314 has advanced to the calibration position (as in step 201). In Figure 3B the illustrated example, the calibration position is the position of the blank holder 314 when the blank holder 314 has contacted the surface of the die 306. The punch 312 and the fastener 320 are held in the retracted position. Although the punch 312 and the fastener 320 are depicted as moving in substantially the same manner as the blank holder 314 (i.e., the punch 312 and the fastener 320 do not move relative to the blank holder 314), this is not necessarily the case. The punch 312 and the fastener 320 can be held in the same position as Figure 3A depicted. In other words, due to the relatively small force applied by the blank holder 314 to the die 306, the upper surface of the die 306 remains in the initial position represented by the reference line 340.

[0132] Referring again to Figure 2, in step 202, the position of the calibration position is measured. In an example where the calibration position is the position of the blank holder 314 when the blank holder 314 contacts the die 306, the position of the surface of the die 306 is measured. In other words, the first position of the surface of the die 306 can be measured. The position of the calibration position can be measured using the blank holder displacement sensor as described above with reference to Figure 1 The calibration position can be measured along the axis along which the blank holder 314 travels.

[0133] In an example where the contact displacement sensor 20 of the fastener installation tool 310 is fixed relative to the blank holder 314, the displacement of the blank holder 314 can be measured by measuring the displacement of the contact displacement sensor 20. For example, as described above, the member 30 can be fixed relative to a fixed point, the contact displacement sensor 20 can be fixed relative to the blank holder 314, and the displacement of the contact displacement sensor 20 relative to the member 30 can be measured to infer the displacement of the blank holder 314. Measuring the position of the calibration position can include measuring the first position of the contact displacement sensor 20. In other words, the first position of the contact displacement sensor 20 (relative to the member 30) can be measured when the blank holder 314 is in the calibration position. The position of the calibration position can be expressed as the distance that the blank holder 314 travels so that the blank holder advances to the calibration position and / or contacts the surface of the die 306.

[0134] Although the die 306 is depicted as having a substantially flat top surface, in some examples, the die can be shaped to facilitate flaring of the self-piercing rivet. Such a die may not contact the workpiece in a uniform manner. There may be areas on the die that are not expected to contact the workpiece (when the workpiece is first placed on the die). The blank holder 314 may contact such a die unevenly (i.e., the portion of the blank holder 314 that can contact the workpiece may not contact the die 306). With such a die, the first position of the surface of the die 306 can be measured at the points on the surface of the die 306 that are expected to contact the workpiece and / or the blank holder 314.

[0135] The position of the calibration position can be measured while the fastener installation tool is arranged as Figure 3B depicted (as described above). For example, the blank holder displacement sensor can be used to determine the position of the blank holder 314 while the blank holder 314 is in the calibration position.

[0136] Method 200 may further include retracting the blank holder 314 such that the workpiece can be inserted between the blank holder 314 and the die 306. In other words, the blank holder 314 can be retracted by at least the thickness of the workpiece. In an example where the method includes using a calibration member, retracting the blank holder 314 can allow removal of the calibration member. Retraction of the blank holder 314 may not always be necessary. For example, in an example where the calibration position is indicated by a first visible tab and a second visible tab, the workpiece can be placed on the die 396 with the blank holder 314 in the calibration position.

[0137] Method 200 may further include positioning the workpiece 330 on the die 306. In other words, the workpiece 330 into which the fastener 320 is to be inserted is positioned in place on the die 306 in a normal manner.

[0138] Figure 3C A system 300 including a fastener installation tool is shown, where the blank holder 314 is in a retracted position. The workpiece 330 has been positioned on the die 306. Although the workpiece 330 is depicted as including two panels (a first panel 331 and a second panel 332), workpieces including additional panels and other materials (e.g., an interlayer material such as an adhesive) can be used. The weight of the workpiece 330 provides a relatively small force (compared to the force applied by the punch 312), and thus the upper surface of the die 306 remains in a position substantially the same as the initial position represented by the reference line 340.

[0139] Referring again to Figure 2 , in step 203, advance the blank holder 314. The blank holder 314 can be advanced such that the blank holder 314 contacts the surface of the workpiece 330. In other words, the blank holder contacts the upward-facing surface of the uppermost panel 331 of the workpiece 330. Such operations of the fastener installation tool 310 (such as retraction of the blank holder 314, placement of the workpiece 330, and advancement of the blank holder 314) are known in the art and can be performed in a typical manner. The blank holder 314 can clamp the workpiece 330 against the die 306. Alternatively, the blank holder 314 can contact the workpiece 330 and provide little or no clamping force.

[0140] Figure 3D A system 300 including a fastener installation tool is shown, where the blank holder 314 is in contact with the surface of the workpiece 330. In Figure 3D 's example, the workpiece 330 is clamped against the die 306 by the force applied by the blank holder 314. As previously described, due to the relatively small force applied by the blank holder 314 to the die 306, the upper surface of the die 306 remains in the initial position represented by the reference line 340.

[0141] In step 204, the position of the surface of workpiece 330 is measured. The position of the surface of workpiece 330 can be measured along the axis along which blank holder 314 travels. The surface of workpiece 330 (i.e., the workpiece measured in step 204) can be the surface of workpiece 330 opposite blank holder 314 and / or the surface of workpiece 330 contacted by blank holder 314.

[0142] The position of the surface of workpiece 330 can be measured in a manner similar to the way the calibration position is measured (as measured in step 202). In other words, the position of the surface of workpiece 330 can be measured by using a blank holder displacement sensor. For example, measuring the position of the surface of workpiece 330 can include measuring the second position of contact displacement sensor 20 relative to member 30. As described above, the measured position of the surface of workpiece 330 can be expressed as the distance that blank holder 314 travels from the calibration position to the position where blank holder 314 contacts the surface of workpiece 330.

[0143] The position of the surface of workpiece 330 can be measured while fastener installation tool 310 is arranged as depicted in Figure 3D and as described above. In other words, the position of the surface of workpiece 330 can be measured while blank holder 314 is in contact with the surface of workpiece 330. Although Figure 3D fastener installation tool 310 is depicted (which includes fastener 320 in a position ready to be inserted into workpiece 330), fastener installation tool 310 does not require fastener 320 to perform method 200 for determining the thickness of workpiece 330.

[0144] In step 205, the thickness of workpiece 330 is determined. Determining the thickness of workpiece 330 can include using the measured position of the calibration position (as measured in step 202) and the measured position of the surface of workpiece 330 (as measured in step 204). In other words, in an example where the calibration position is the position of blank holder 314 when blank holder 314 contacts the surface of die 306, the difference between the measured position of the calibration position and the measured position of the surface of workpiece 330 can correspond to the thickness of workpiece 330. Such a determined thickness can be referred to as an absolute thickness because the determined thickness is not determined with reference to the thickness of another object (i.e., a calibration member).

[0145] Alternatively, the determined thickness can be a relative thickness. For example, (as discussed above) the calibration position can be measured by using a calibration member and / or alignment marks. In such an example, the determined thickness of workpiece 330 (as determined in step 205) can be related to the thickness of the calibration member and / or correspond to the thickness of the alignment marks. For example, workpiece 330 can be determined to be 1 mm thicker than the thickness of the calibration member.

[0146] Method 200 may further include receiving the thickness of the calibration member and / or the thickness corresponding to the alignment mark (i.e., the thickness of the calibration member to extend from the surface of the die 306 to the alignment mark). For example, the thickness of the calibration member can be measured separately, and the measured thickness can be used in method 200. For example, the measured thickness can be stored in a memory and retrieved from the memory during method 200. Method 200 may further include determining an absolute thickness based on the relative thickness. For example, the calibration member can be 1 mm thick, and the workpiece 330 can be determined to have a relative thickness of 4.6 mm (relative to the calibration member). The workpiece 330 can be determined to have an absolute thickness of 5.6 mm.

[0147] The dimension of the workpiece 330 corresponding to the determined thickness can be a dimension parallel to the movement of the blank holder 14. The thickness of the workpiece 330 can be determined when the fastener installation tool 310 is in any arrangement. For example, the thickness of the workpiece 330 can be determined immediately after the position of the surface of the workpiece 330 is measured (i.e., before the fastener is inserted). Thus, when the thickness of the workpiece 330 is determined, the fastener installation tool 310 can be arranged as Figure 3D depicted. Alternatively, the thickness of the workpiece 330 can be determined at a later point (e.g., after the fastener 320 has been inserted into the workpiece 330).

[0148] In an optional step 206, the fastener 320 can be inserted into the workpiece 330. The punch 312 of the fastener installation tool 310 can be used to insert the fastener 320. The fastener 320 can be a self-piercing rivet. In an example where the fastener 320 is a self-piercing rivet, the punch 312 can apply a force to the self-piercing rivet 320 such that the self-piercing rivet 320 is inserted into an area near or directly above the die 306 in the workpiece 330. When the self-piercing rivet 320 is inserted into the workpiece 330, the self-piercing rivet 320 can flare outwards. In other words, a portion of the self-piercing rivet 320 can be forced to extend radially outwards from the axis passing through the self-piercing rivet 320.

[0149] Figure 3E A system 300 including a fastener installation tool 310 is depicted, where the workpiece 306 is clamped against the die 306 by a blank holder 314. The punch 312 has advanced from an initial position and inserted the fastener 320 into the workpiece 330. Although Figure 3EThe punch 312 is depicted as not protruding from the hole of the blank holder 314, but this is merely exemplary and may not be the case. For example, the punch 312 may protrude from the hole of the blank holder 314 (at a position corresponding to the maximum displacement of the punch 312) such that the fastener 320 can be inserted into the workpiece 330 in the correct manner regardless of any deformation of the panels 331, 332 of the workpiece 330. Due to the relatively high force applied by the punch 312, the system deflects. As a result, the die 306 moves away from the initial position indicated by the reference line 340. Although Figure 3E the example of Figure 3E shows a portion of the punch 312 aligned with the reference line 340, the system may deflect more or less than shown.

[0150] The fastener 320 can be inserted before and / or after determining the thickness of the workpiece 330. The thickness of the workpiece 330 can be determined multiple times (i.e., one or more of steps 201, 202, 203, 204, and 205 can be performed multiple times). For example, the position of the surface of the workpiece 330 can be measured for the first time, the thickness of the workpiece 330 can be determined for the first time, and the first thickness can be used to determine whether the workpiece 330 is suitable for the fastener 320 to be inserted. The fastener 320 can be inserted. The position of the surface of the workpiece 330 can be measured for the second time, the thickness of the workpiece 330 can be determined for the second time, and the second thickness of the workpiece 330 can be used to determine the tool offset (as explained in more detail below with reference to method 400). Alternatively, the thickness of the workpiece 330 can be determined once and used to determine whether the workpiece 330 is suitable for the fastener 320 to be inserted and to determine the tool offset.

[0151] In optional step 207, the blank holder 314 and / or the punch 312 can be retracted. In other words, the blank holder 314 and the punch 312 can be retracted to the initial position to prepare for method 200 and thus start again with another workpiece. The position to which the blank holder 314 retracts can be a calibration position.

[0152] Figure 3F The system 300 is depicted with the blank holder 314 and the punch 312 retracted. As Figure 3F shown, the fastener 320 remains inserted into the workpiece 330, and the workpiece 330 can be removed from the die 306. The blank holder 314 and / or the punch 312 can be retracted at any appropriate time after the fastener 320 has been inserted into the workpiece 330. Once the punch 312 stops applying force, the die 306 can return to the initial position. Alternatively, method 200 can further include resetting the system 300, i.e., returning the die 306 to the initial position. In other words, the die 306 can be moved such that the upper surface of the die 306 is aligned with the reference line 340.

[0153] The determined thickness can be stored. For example, the determined thickness can be stored in a computer-readable memory. The determined thickness can be stored in a database together with other characteristics related to the fastener 320, the joint, the workpiece 330, and / or the fastener insertion tool 310. For example, an identifier corresponding to the workpiece 330, the position of the joint in the workpiece 330, and the type of the fastener 320 can also be stored in the database.

[0154] The determined thickness can be tested against a predetermined value in a threshold test. For example, the threshold test can test whether the determined thickness of the workpiece 330 is at least one of the following: less than; greater than; less than or equal to; greater than or equal to; and / or equal to one or more predetermined values. The threshold test can be one of multiple threshold tests. In other words, multiple threshold tests can be applied to the determined thickness, and the results can be combined using, for example, Boolean logic. Each threshold test can provide a binary result (i.e., 0 or 1). A result of 1 can indicate that the threshold test has passed (i.e., the condition tested in the threshold test is met). The result of the threshold test can be represented as a warning indication and / or a fault indication. The result of the threshold test can be used to indicate a recommendation and / or a need for a specific action. The result of the threshold test can be used to cause a specific action to be performed.

[0155] Based on the result of the threshold test applied to the determined thickness, it can be determined that the workpiece 330 should be replaced. For example, the threshold test can be used to test whether the determined thickness of the workpiece 330 falls within a specific value range. In other words, the nominal thickness can be 6 mm, and the corresponding tolerance can be 10% (i.e., it can be required that the determined thickness has a value of at least 5.4 mm and less than 6.6 mm). A workpiece 330 with a determined thickness of 5.6 mm can pass such a threshold test and the workpiece 330 can be used in a normal manner. A workpiece 330 with a determined thickness of 7 mm may not pass (i.e., does not meet) such a threshold test. In the case where such a threshold test fails, the workpiece 330 can be identified as not suitable for use in the process and / or the product. An indication can be provided to indicate that the workpiece 330 should be replaced. Additionally or alternatively, the workpiece 330 can be replaced. In other words, the workpiece 330 can be removed from the process (and not used to build the product being manufactured), and a different workpiece 330 can be used.

[0156] Based on the results of a threshold test applied to a determined thickness, it can be determined that the fastener installation tool 310 needs maintenance. If such a threshold test is satisfied, it can be determined that the fastener installation tool 310 is within normal operating conditions. Alternatively, if such a threshold test fails, it can be determined that the fastener installation tool 310 needs maintenance. An indication can be provided to indicate that the fastener installation tool 310 needs maintenance and / or what specific maintenance is required. Additionally or alternatively, maintenance can be performed. In other words, the fastener installation tool 310 can perform the required maintenance on itself or cause the required maintenance to be performed.

[0157] Based on the results of a threshold test applied to a determined thickness, it can be determined that parameters associated with the fastener installation tool 310 should be adjusted. For example, the threshold test can be used to test whether the determined thickness of the workpiece 330 is less than a value such as 5.4 mm. If such a threshold test is satisfied, the fastener installation tool 310 can, for example, reduce the force used to insert the fastener 320 into the workpiece 330. As another example, the threshold test can be used to test whether the determined thickness of the workpiece 330 is greater than a value such as 6.6 mm. If such a threshold test is satisfied, the fastener installation tool 310 can, for example, increase the force used to insert the fastener 320 into the workpiece 330. If any of the exemplary threshold tests described herein fail (i.e., the determined thickness of the workpiece 330 is greater than or equal to 4 mm and less than or equal to 5 mm), the determined thickness of the workpiece 330 can be determined to be acceptable and no adjustment to the parameters associated with the fastener installation tool 310 need be made. Other exemplary parameters that can be adjusted include, for example, the type of fastener inserted (i.e., a first type of rivet can be changed to a second type of rivet), the type of die on the fastener installation tool 310, the amount of adhesive disposed between the panels 331, 332 of the workpiece 330, the end position of the punch 312, and / or the clamping force applied by the blank holder 314. The parameters can be changed for the workpiece 330 for which the thickness has been determined or in relation to the workpiece 330. In other words, the fastener 310 can be inserted into the measured workpiece 330 with an increased force. Additionally or alternatively, the parameters can be changed for subsequent workpieces. In other words, the fastener can be inserted into a workpiece after the measured workpiece 330 with an increased force.

[0158] Figure 4 A flowchart of a method 400 for determining tool offset is depicted. In step 401, the fastener 320 is inserted into the workpiece 330. In step 402, the thickness of the workpiece 330 is determined. In step 403, the position of the top surface of the fastener 320 is measured. In step 404, the head height of the fastener 320 is received. In step 405, the tool offset is determined. In optional step 406, an offset factor can be determined.

[0159] In step 401, the fastener 320 is inserted into the workpiece 330. As described above with respect to method 200, the fastener 320 can be inserted into the workpiece 330. In an example of method 400 in which an offset factor is determined, inserting the fastener into the workpiece 330 can further include determining the peak force applied to the fastener 320 by the punch 312.

[0160] The peak force applied to the fastener 320 by the punch 312 can be measured using a force sensor. The force can be measured continuously (or discretely at a high sampling rate) over time, and the maximum recorded force can be determined. Alternatively, the force can be measured at one or more time points. The one or more time points can be determined (i.e., triggered) by other measurements. For example, the position measurement of the motor 8 (discussed above with respect to the force sensor) can allow the displacement of the punch 312 to be measured. The measured displacement of the punch 312 can be used to determine the travel speed of the punch 312, and the determined speed can be used to determine the time points at which the force should be measured (by the force sensor) or calculated (based on the model of the rivet insertion tool 2). For example, the speed of the punch 312 can be determined, and when the speed of the punch 312 drops below a value such as 4 mm / s, the calculation of the force applied by the punch 312 to the fastener 320 can be triggered.

[0161] In step 402, the thickness of the workpiece 330 is determined. The thickness of the workpiece 330 can be determined as described above with respect to method 200 (specifically step 205).

[0162] In step 403, the position of the top surface of the fastener 320 is measured. The top surface of the fastener 320 can be the surface of the fastener 320 that is opposite to and / or in contact with the punch 312. In other words, the position of the surface of the fastener 320 that is opposite to the punch 312 can be measured. When the blank holder 314 is in the retracted position (i.e., as depicted in Figure 3A ), the top surface of the fastener 320 can be the surface of the fastener 320 that is closest to the blank holder 314.

[0163] The position of the top surface of the fastener 320 can be measured relative to the measured position of the surface of the die 306 (as measured in step 202). The position of the top surface of the fastener 320 can be measured relative to a calibration position. The position of the top surface of the fastener 320 can be measured using a punch displacement sensor. When the displacement of the punch 312 positions the fastener 320, the maximum displacement of the punch 312 can correspond to the position of the top surface of the fastener 320. Thus, it can be assumed that the maximum displacement of the punch 312 corresponds to the position of the top surface of the fastener 329.

[0164] Alternatively, the position of the top surface of the fastener 320 can be measured using a blank holder displacement sensor. For example, the blank holder 314 can be retracted and the position of the workpiece 330 (and the fastener 320) can be moved such that when the blank holder 314 advances, the blank holder 314 contacts the top surface of the fastener 320.

[0165] In step 404, the head height of the fastener 320 can be received and / or measured. The measured head height of the fastener 320 can be manually measured, for example, by an operator using a (dial test indicator) DTI gauge, and the measured head height can be provided as an input to the fastener installation tool 310 via a human-machine interface, for example. Alternatively, other measuring devices can be used, for example, a measuring device that uses optical effects to measure the head height of the fastener 320.

[0166] In step 405, the tool offset can be determined. The tool offset can correspond to the change in the end position of a component of the fastener installation tool 310 relative to the starting position due to the insertion of the fastener. In other words, the components of the fastener installation tool 310 can move due to the forces applied to the fastener 320 during the insertion of the fastener 320. The end position can be the position of the component before the punch 312 and the blank holder 314 are retracted. In other words, the end position can correspond to the position of the component as depicted in Figure 3E (for simplicity, the movement due to tool offset is not depicted in any of Figure 3A - Figure 3F ). Examples of components that can move due to offset include the C-frame, the die 306, and / or one or more linkages within the fastener installation tool 310. Since the distance between the end position of the end of the punch 320 and the end position of the die 306 is generally equal to the sum of the thickness of the workpiece 330 and the head height of the fastener 320, measuring (or determining) each of the following: the end position of the punch 320; the thickness of the workpiece 330 and the head height of the fastener 320 can be used to determine the tool offset.

[0167] By using the measured head height of the fastener 320, the measured thickness of the workpiece 330, and the measured position of the top surface of the fastener 320, the tool offset can be determined. In other words, the tool offset TD can be determined as:

[0168] TD = HH + MT - ED

[0169] where: HH is the measured head height of the fastener 320; MT is the determined thickness of the workpiece 330; and ED is the determined position of the top surface of the fastener 320.

[0170] As described above, the thickness of the workpiece 330 can be determined after the fastener 320 is inserted into the workpiece 330. Advantageously, by performing the steps of method 400 in this order, any effect on the determined tool offset due to a change in the thickness of the workpiece 330 caused by the insertion of the fastener 320 will be minimized. Minimizing can include completely eliminating any effect on the tool offset due to a change in the thickness of the workpiece 330 caused by the insertion of the fastener 320. Alternatively, the thickness of the workpiece 330 can be determined before the fastener 320 is inserted into the workpiece 330. Advantageously, by performing the method steps in this order, the repetition of measurements can be reduced, and method 400 can be performed faster than otherwise.

[0171] The tool offset can be used to compare the offset of the fastener installation tool 310 and / or determine the properties of the fastener 320, the joint, the workpiece 330, and / or the fastener installation tool 310 when different fasteners are inserted. For example, the tool offset can be used to determine an offset factor, and the offset factor can be used to determine the head height of the fastener 320 (as described below). As another example, the tool offset can indicate wear of components of the fastener installation tool 310, and a change in the tool offset (for similar fasteners and workpieces) over time can indicate that one or more components of the fastener installation tool 310 need maintenance and / or replacement.

[0172] Method 400 can further include determining an offset factor corresponding to the offset of the fastener installation tool 310 relative to the peak force applied to the fastener 320 by the punch 312. The offset factor DF can be determined as:

[0173] DF = TD ÷ PF

[0174] where PF is the determined peak force. The tool offset can be used to explicitly (or alternatively, implicitly) determine the offset factor. In other words, the offset factor can also be determined as:

[0175] DF = (HH + MT - ED) ÷ PF

[0176] For example, for a measured head height of 0.02 mm, a determined thickness of 5.63 mm, a measured punch position of 3.25 mm, and a measured peak force of 57.40 kN, the tool offset can be determined to be 2.40 mm and the offset factor can be determined to be 0.042 mm / kN.

[0177] The tool offset and / or offset factor can be determined at regular intervals or in response to a specific event. For example, the tool offset and / or offset factor can be determined after a set number of fasteners have been inserted (e.g., after every 250,000 or 500,000 fasteners have been inserted). The tool offset and / or offset factor can be determined after maintenance work has been performed on the fastener installation tool 310 and / or the die 306. The tool offset and / or offset factor can be determined when using different batches of components (e.g., when using different batches of fasteners 320 and / or workpieces 330 including different batches of panels 331, 332).

[0178] The tool offset and / or offset factor can be stored. For example, the tool offset and / or offset factor can be stored in a computer-readable memory. The tool offset and / or offset factor can be stored in a database along with other characteristics related to the fasteners 320, joints, workpieces 330, and / or the fastener insertion tool 310. For example, the identifier corresponding to the workpiece 330, the location of the joints in the workpiece 330, and the type of the fasteners 320 can also be stored in the database. Other attributes can include, for example, the type of the die 306 and / or the type of the adhesive.

[0179] The tool offset and / or offset factor can be tested against a predetermined value in a threshold test in a manner similar to that described above for the determined thickness of the workpiece 330. The result of the threshold test can be represented as a warning indication and / or a fault indication. The result of the threshold test can be used to indicate a recommendation and / or the need for a specific action. The result of the threshold test can be used to cause a specific action to be performed.

[0180] Based on the result of the threshold test applied to the tool offset and / or offset factor, it can be determined that the workpiece 330 should be replaced. For example, the threshold test can be used to test whether the tool offset and / or offset factor falls within a specific value range. In the case where such a threshold test fails, a component (e.g., the workpiece 330, the fastener installation tool 310, or a part of the workpiece 330 or the fastener installation tool 310) can be identified as not suitable for use in the process and / or the product. An indication can be provided to indicate that the component should be replaced. Additionally or alternatively, the component can be replaced. In other words, the component can be removed from the process (and not used in constructing the product being manufactured), and a different component can be used. As an example, the C-shaped frame 4 can be a component that can be identified as not suitable for use in this process.

[0181] Based on the results of threshold tests applied to tool offset and / or offset factor, it can be determined that the fastener installation tool 310 needs maintenance. For example, the threshold test can be used to test whether the determined tool offset is less than a threshold tool offset value such as 2 mm. If such a threshold test is met, it can be determined that the fastener installation tool 310 is within normal operating conditions. Alternatively, if such a threshold test fails, it can be determined that the fastener installation tool 310 needs maintenance. An indication can be provided to indicate that the fastener installation tool 310 needs maintenance and / or what specific maintenance is required. Additionally or alternatively, maintenance can be performed. In other words, the fastener installation tool 310 can perform the required maintenance on itself or cause the required maintenance to be performed.

[0182] Based on the results of threshold tests applied to tool offset and / or offset factor, it can be determined that parameters associated with the fastener installation tool 310 should be adjusted. For example, the threshold test can be used to test whether the tool offset is greater than a value such as 3 mm. If such a threshold test is met, the fastener installation tool 310 can, for example, increase the force used to insert the fastener 320 into the workpiece 330. As another example, the threshold test can be used to test whether the tool offset is less than a value such as 2 mm. If such a threshold test is met, the fastener installation tool 310 can, for example, decrease the force used to insert the fastener 320 into the workpiece 330. If any of the exemplary threshold tests described herein fail, it can be determined that the tool offset and / or offset factor is acceptable and that the parameters associated with the fastener installation tool 310 need not be adjusted. Other exemplary parameters that can be adjusted include, for example, the type of fastener inserted (i.e., a first type of rivet can be changed to a second type of rivet), the amount of adhesive disposed between the panels 331, 332 of the workpiece 330, the end position of the punch 312, and / or the clamping force applied by the blank holder 314.

[0183] Figure 5 A method 500 for determining attributes of a fastener 320 is depicted. In step 501, a stored offset factor is received. In step 502, a determined peak force is received. In step 503, a determined thickness of the workpiece is received. In step 504, a determined position 504 of the top surface of the fastener is received. In step 505, the head height is determined.

[0184] Reference will be made again to Figure 3A - Figure 3F to describe method 500.

[0185] Method 500 can be used to determine the properties of a fastener 320 that has been inserted into a workpiece 330. For example, a peak force (for inserting the fastener 320 into the workpiece 330) can be determined during the insertion of the fastener 320, and the determined peak force can be used in Method 500 (at step 505). Alternatively, Method 500 can include inserting the fastener 320 and measuring the peak force during the insertion of the fastener 320. As a further alternative, the fastener 320 can be inserted with a predetermined peak force, and the predetermined peak force can be used in Method 500. The fastener 320 can be inserted by the fastener installation tool 310 using an applied predetermined torque.

[0186] In step 501, a stored offset factor is received. The stored offset factor can have been pre-determined as in Method 400 (and as described above). The stored offset factor can be associated with the location (or planned location) of the fastener 320 at the workpiece 330 and / or a similar workpiece. In other words, if the fastener 320 is (or is to be) inserted at a different location of the workpiece 330, a different offset factor can be received. If the fastener 320 is (or is to be) inserted at a similar location in a similar workpiece 330, the same offset factor can be received. Alternatively, the offset factor can be consistent at the workpiece 330 and / or a similar workpiece.

[0187] Method 500 can further include receiving and / or determining one or more characteristics of the fastener 320, the joint (i.e., the joint made by the fastener 320), and / or the workpiece 330 (i.e., the workpiece 330 into which the fastener 320 has been or is to be inserted). For example, the location of the joint in the workpiece 330 can be determined and used to determine which stored offset factor to receive from a database (the database stores multiple offset factors, each with a corresponding location).

[0188] For all systems including the same and / or similar types of fastener installation tool 310, workpiece 330, and fastener 320, the offset factor of the system 300 (including the fastener installation tool 310, workpiece 330, and fastener 320) can be constant (or approximately constant). In other words, the offset factor can allow the head height of the fastener 320 to be inferred without directly measuring the head height of the fastener 320.

[0189] In step 502, the determined peak force is received. The determined peak force can correspond to the peak force applied by the punch 312 of the fastener installation tool 310 to the fastener 320. The determined peak force can be determined in the same manner as described above.

[0190] In step 503, receive the determined thickness of workpiece 330. The thickness of workpiece 330 can be determined in the same manner as described above in method 200 and / or in step 402.

[0191] In step 504, receive the determined position of the top surface of fastener 320. The position of the top surface of fastener 320 can be determined in the same manner as described above in step 403.

[0192] In step 505, determine the head height of fastener 320. The head height HH of fastener 320 can be determined as:

[0193] HH = (DF × PF) - MT + ED

[0194] where: DF is the stored offset factor; PF is the measured peak force; MT is the determined thickness of workpiece 330; and ED is the measured position of the top surface of fastener 320. For example, for a stored offset factor of 0.042 mm / kN, a measured peak force of 57.4 kN, a determined thickness of workpiece 330 of 5.63 mm, and a measured position of the top surface of fastener 320 of 3.25 mm, the head height can be determined to be 0.02 mm. Thus, the head height of fastener 320 can be determined by using other measured values, avoiding the need to directly measure the head height itself.

[0195] The head height of fastener 320 can represent an attribute of workpiece 330 and / or a joint made at workpiece 330. For example, the head height can represent the strength of the joint. The head height can also be referred to as the position of the top surface of the head of fastener 320 relative to the top surface of workpiece 330 in the region near fastener 320. The region near fastener 320 can be the region immediately surrounding fastener 320, or can be a region beyond the region deformed due to the insertion of fastener 320. As an alternative (or supplement) to destructive testing, the determined head height of the fastener can provide an indication of the strength (or another attribute) of the joint. For example, a destructive test can be employed to determine the head height of a first fastener 320 in a first workpiece 330, and the strength of the corresponding first joint can be determined. The head height of a second fastener 320 at a second workpiece 330 can be determined, and used to infer the strength of the corresponding second joint based on the head height and strength of the first joint.

[0196] The determined head height can be stored. For example, the determined head height can be stored in a computer-readable memory. The determined head height can be stored in a database together with other characteristics related to the fastener 320, the joint, the workpiece 330, and / or the fastener insertion tool 310. For example, the identifier corresponding to the workpiece 330, the position of the joint in the workpiece 330, and the type of the fastener 320 can also be stored in the database.

[0197] The determined head height can be tested against a predetermined value in a threshold test in a manner similar to that described above for the determined thickness of the workpiece 330. The result of the threshold test can be expressed as a warning indication and / or a fault indication. The result of the threshold test can be used to indicate a recommendation and / or the need for a specific action. The result of the threshold test can be used to cause a specific action to be performed.

[0198] Based on the result of the threshold test applied to the determined head height, it can be determined that the workpiece 330 should be replaced. For example, the threshold test can be used to test whether the determined head height falls within a specific value range. In other words, the nominal head height can be 0.02 mm, and the corresponding tolerance can be 10%. The determined head height may need to have a head height of at least 0.018 mm and less than 0.022 mm. The workpiece 330 with a determined head height of 0.019 mm can pass such a threshold test and be used in a normal manner. The fastener 320 with a determined head height of 0.023 mm may not pass (i.e., not meet) such a threshold test. In the case where such a threshold test fails, the workpiece 330 and / or the fastener 320 can be identified as not suitable for use in the process and / or the product. An indication can be provided to indicate that the workpiece 330 and / or the fastener 320 should be replaced. Additionally or alternatively, the workpiece 330 and / or the fastener 320 can be replaced. In other words, the workpiece 330 and / or the fastener 320 can be removed from the process (and not used in constructing the product being manufactured), and different workpiece 330 and / or fastener 320 can be used.

[0199] Based on the results of a threshold test applied to the determined head height, it can be determined that the fastener installation tool 310 requires maintenance. For example, the threshold test can be used to test whether the determined head height is above and / or below a threshold head height value, such as 0.025 mm. If such a threshold test is satisfied, it can be determined that the fastener installation tool 310 is within normal operating conditions. Alternatively, if such a threshold test fails, it can be determined that the fastener installation tool 310 requires maintenance. An indication can be provided to indicate that the fastener installation tool 310 requires maintenance and / or what specific maintenance is required. Additionally or alternatively, maintenance can be performed. In other words, the fastener installation tool 310 can perform the required maintenance on itself or cause the required maintenance to be performed.

[0200] Based on the results of a threshold test applied to the determined head height, it can be determined that parameters associated with the fastener installation tool 310 should be adjusted. For example, the threshold test can be used to test whether the determined head height of the fastener 320 is less than a value, such as 0.025 mm. If such a threshold test is satisfied, the fastener installation tool 310 can, for example, reduce the force used to insert the fastener 320 into the workpiece 330. As another example, the threshold test can be used to test whether the determined head height of the fastener 320 is greater than a value, such as 0.03 mm. If such a threshold test is satisfied, the fastener installation tool 310 can, for example, increase the force used to insert the fastener 320 into the workpiece 330. If any of the exemplary threshold tests described herein fail, it can be determined that the determined head height of the fastener 320 is acceptable and that the parameters associated with the fastener installation tool 310 need not be adjusted. Other exemplary parameters that can be adjusted include, for example, the type of fastener 320 being inserted (i.e., a first type of rivet can be changed to a second type of rivet), the type of die 306, the amount of adhesive placed between the panels 331, 332 of the workpiece 330, the end position of the punch 312, and / or the clamping force applied by the blank holder 314.

[0201] Figure 6 is a flowchart depicting a method 600 for determining the force for inserting the fastener 320. In step 601, the desired head height of the fastener 320 is received. In step 602, the thickness of the workpiece 330 is received. In step 603, an offset factor is received. In step 604, the desired position of the top surface of the fastener 320 is received. In step 605, the force applied to the fastener 320 is determined.

[0202] In step 601, the required head height of the fastener 320 is received. The required head height can be determined based on one or more characteristics of the workpiece 330 and / or the joint in the workpiece 330. For example, it is known that the head height of the fastener 320 corresponds to the strength of the joint made by the fastener 320 at the workpiece 330. The joint may need to have a minimum strength, and the minimum strength can be used to determine the required head height of the fastener 320. Additionally or alternatively, the workpiece 330 (once assembled into the product) can be expected to move relative to another part of the product, and the expected movement can be used to determine the required head height of the fastener 320. For example, the workpiece 330 can be a door frame of a car, and the corresponding car door can be expected to move relative to the door frame. Such movement can provide the maximum head height of the fastener 320 inserted into the workpiece 330. In other words, if the fastener 320 has a head height higher than the maximum value, the car door 320 may smear the door frame and prevent the required movement of the car door (e.g., the car door may not be able to open and / or close).

[0203] In step 602, the thickness of the workpiece 330 is received. The received thickness of the workpiece 330 can have been determined as in the above-described method 200. Additionally or alternatively, the thickness of the workpiece 330 can be determined using any method or device known in the art. For example, a set of calipers can be used. Additionally or alternatively, the thickness of the workpiece 330 can be the thickness of a nominal workpiece.

[0204] In step 603, an offset factor is received. The received offset factor can be determined as in the above-described method 200. The offset factor can be received in a manner similar to receiving the stored offset factor (in step 501). The offset factor can correspond to the position of the joint in the workpiece 330, one or more properties of the workpiece 330 (e.g., the hardness of the panels 331, 332 at the workpiece 330), one or more properties of the fastener installation tool 310 (e.g., the stiffness of the C-shaped frame 4), and / or one or more properties of the fastener 320 (e.g., the hardness or flaring of the fastener 320).

[0205] In step 604, the desired position of the top surface of the fastener 320 is received. The desired position of the top surface of the fastener 320 can be determined based on one or more characteristics of the workpiece 330 and / or the fastener 320. Additionally or alternatively, previously inserted fasteners in the workpiece can be used to determine the desired position of the top surface of the fastener 320.

[0206] In step 605, the force applied to the fastener 320 is determined. In other words, after inserting the fastener 320 into the workpiece 330 using the determined force, the head height of the fastener 320 can be equal to (or approximately equal to) the required head height. The force PF can be determined as:

[0207]

[0208] Wherein, HH is the required head height of the fastener, DF is the offset factor, MT is the thickness of the workpiece, and ED is the position of the top surface of the fastener.

[0209] Method 600 may further include inserting fastener 320 into workpiece 330 using punch 312 of fastener installation tool 310. The determined force (i.e., the force determined in step 605) may be applied to fastener 320 using punch 312.

[0210] Figure 7 is a flowchart of method 700 for depicting attributes of workpiece 330 or a joint made at workpiece 330 (i.e., the joint made by fastener 320). In step 701, the blank holder of fastener installation tool 310 is brought into contact with the surface of workpiece 330. In step 702, a force is applied to blank holder 314. In step 703, the movement of workpiece 330 is detected. In optional step 704, a predetermined feature may be determined to be present in the detected movement. In step 705, the attributes of workpiece 330 or the joint made at workpiece 330 are determined. In optional step 706, fastener 320 may be inserted into workpiece 330.

[0211] In step 701, blank holder 314 of fastener installation tool 310 is brought into contact with the surface of workpiece 330. In other words, blank holder 314 may contact the surface of workpiece 330 as Figure 3D depicted. Blank holder 314 may be moved to contact the surface of workpiece 330 at a low speed and / or with a low force such that the time point at which blank holder 314 contacts the surface of workpiece 330 can be identified and / or measured. For example, after contacting the surface of workpiece 330, the speed of blank holder 314 or the force applied to blank holder 314 may be changed.

[0212] In step 702, a force is applied to blank holder 314. The force may be applied to 314 in the axial direction of blank holder 314 towards workpiece 330. In other words, blank holder 314 may have an axis and blank holder 314 may move along (or parallel to) that axis. The force may be applied to 314 along the axis towards workpiece 330. The force may be a consistent force, i.e., during the time of applying the force, the force may have a constant magnitude and / or direction. The force may be continuously applied when the movement of workpiece 330 is detected. In other words, steps 702 and 703 may be performed simultaneously. Alternatively, the movement of workpiece 330 may be detected after the application of the force has stopped.

[0213] The magnitude of the applied force can be selected such that the applied force can cause some movement and the movement can be detected. For example, the applied force can be sufficient to close the panel gap (i.e., the void space region between adjacent panels 331, 332 of the workpiece 330) within a measurable time period. As another example, the applied force can have a magnitude that is large enough to cause a measurable oscillation in the workpiece 330 but small enough not to critically damp or overdamp the oscillation. In other words, if the applied force is too large, the applied force will prevent the panels 331, 332 from oscillating.

[0214] In step 703, the movement of the workpiece 330 is detected. This movement can be caused by the force applied to the blank holder 314. This movement can be detected by measuring the displacement of the blank holder 314. In other words, when the blank holder 314 contacts the workpiece 330 and when a force is applied to the blank holder 314 in the direction of the workpiece 330, the movement of the workpiece 330 will cause the movement of the blank holder 314. This movement can be in a straight line with the axis of the blank holder 314. The movement of the blank holder 314 can change the displacement of the blank holder 314. The change in the displacement of the blank holder 314 can be measured by a blank holder displacement sensor. For example, in the example where the workpiece 330 oscillates, the blank holder 314 can also oscillate, and the movement of the blank holder 314 can be detected by the blank holder displacement sensor.

[0215] In an optional step 704, a predetermined feature can be determined to be present in the detected movement. In other words, a predetermined feature can be identified in the detected movement. For example, the predetermined feature can include a consistent movement in a single direction. As an alternative, the predetermined feature can include an oscillation.

[0216] In step 705, the properties of the workpiece 330 or the joint made at the workpiece 330 are determined. The properties can be determined based on the detected movement (i.e., the movement detected in step 703) and / or the determination that a predetermined feature is present in the detected movement. The properties can be, for example, the presence of a panel gap, the size of the panel gap, the presence of an adhesive, and / or the amount of adhesive present. Additionally or alternatively, the properties can be the stiffness, ductility, and / or strength (e.g., ultimate tensile strength) of one or more of the panels 331, 332 in the workpiece 330.

[0217] In optional step 706, fastener 320 can be inserted into workpiece 330. For example, punch 312 of fastener installation tool 310 can be used to insert fastener 320. A force can be applied to blank holder 314 before, during, and / or after inserting fastener 320. In an example where method 700 includes inserting fastener 320 into workpiece 330, the movement of workpiece 330 can include movement in response to fastener 320 being inserted (by punch 312 of fastener installation tool 310) into workpiece 330. In an example where method 700 includes inserting fastener 320 into workpiece 330, the property can be deformation and / or offset of workpiece 330 (or panels 331, 332 of workpiece 330). The deformation can correspond to underhead clearance, bottom fill, and / or overfill in the area near fastener 320.

[0218] As a first example of method 700, workpiece 330 can include two panels 331, 332 with a panel gap therebetween. Blank holder 314 can contact the surface of workpiece 330, and blank holder 314 can apply a force toward workpiece 330 to blank holder 314. Under the applied force, panels 331, 332 of workpiece 330 can be squeezed together, thereby reducing or closing the panel gap. In other words, panels 331, 332 can gradually move together, thereby causing a similar gradual movement of blank holder 314. The gradual movement of blank holder 314 can be detected by a blank holder displacement sensor, and the detected movement can be used to identify the presence of the panel gap. The force can be applied until panels 331, 332 stop moving, for example, due to the panel gap closing. The detected movement can also be used to determine the size of the panel gap that existed before the force was applied.

[0219] As a second example of method 700, workpiece 330 can include two panels 331, 332 with an adhesive therebetween. Blank holder 314 can contact the surface of workpiece 330, and blank holder 314 can apply a force toward workpiece 330 to blank holder 314. Under the applied force, panels 331, 332 of workpiece 330 can be squeezed together, thereby reducing the amount of adhesive between opposing points on the two panels 331, 332. In other words, panels 331, 332 can gradually move together, thereby causing a similar gradual movement of blank holder 314. The adhesive can be squeezed into the space between the two panels 331, 332, i.e., spread the adhesive in a more uniform manner. Additionally or alternatively, the adhesive can be extruded from the space between the two panels 331, 332. The gradual movement of blank holder 314 can be detected by a blank holder displacement sensor, and the detected movement can be used to determine the presence of the adhesive.

[0220] As a third example of method 700, the panels 331, 332 of the workpiece 330 can be in a first position. After the fastener 320 is inserted into the workpiece 330, the panels 331, 332 of the workpiece 330 can have moved to a second position. In other words, a portion of the uppermost panel 331 can move downward such that the blank holder 314 moves downward by a corresponding amount. The downward movement of the blank holder 314 can be detected by a blank holder displacement sensor. The detected movement can be used to determine that the material within the workpiece 330 deforms during the insertion of the fastener 320.

[0221] As a fourth example of method 700, the fastener 320 can be inserted into the workpiece 330. When the fastener 320 is inserted, a portion of the workpiece 330 can be offset upward. For example, a first portion of the workpiece 330 (i.e., near the location where the fastener 320 is inserted) can be pushed downward from a first position into a die 306 having a recessed portion. The shape of the die 306 (particularly the recessed portion) can cause a second portion of the workpiece 330 to be offset upward from a corresponding first position (i.e., further away from the location where the fastener 320 is inserted). Once the fastener 320 has been inserted into the workpiece 330 (and the punch 312 has retracted), the first portion of the workpiece 330 can no longer be pushed downward into the die 306. The first portion of the workpiece 330 can return to the first position, and the second portion of the workpiece 330 can return to the corresponding first position. This movement of the first or second portion of the workpiece 330 can cause a corresponding movement of the blank holder 314 and can be detected by the blank holder displacement sensor. The detected movement can be used to determine the brittleness and / or hardness of the panels 331, 332 of the workpiece 330.

[0222] Figure 8 is a flowchart depicting method 800 for calculating adjustments and applying the adjustments to a fastener installation tool and / or workpiece. In step 801, a determined property is compared with a predetermined property. In step 802, an adjustment is calculated. In step 803, the adjustment is applied.

[0223] As described above, the performance of a fastener installation tool can vary depending on the condition of the tool, e.g., whether the tool is cold, warming up, or hot. By employing method 800, the varying performance of the tool can be compensated for. In particular, the effect of frictional losses can be indirectly determined by measuring a first parameter and comparing it with a predetermined parameter. Thus, calculating and applying an adjustment thereto provides a method of compensation. Such a method of compensation can beneficially improve the performance of the tool.

[0224] As shown by the dashed lines, method 800 can be iteratively performed to form a feedback loop. That is, for the same or consecutive fasteners, the steps of comparing, calculating, and applying the adjustment can be repeated any number of times. In this way, the method can converge on the parameters for inserting the fastener to help minimize tool wear while ensuring that the fastener is inserted according to the predetermined properties. For example, the tool can insert the fastener with the minimum necessary force to the optimal head height.

[0225] In step 801, the determined property is compared with the predetermined property. Generally, both the determined property and the predetermined property can involve the same or similar properties. For example, the determined property can be the determined head height of the first fastener, and the determined head height can be determined by using method 500. The predetermined property can be the predetermined head height. As an alternative example, the determined property can be the determined thickness of the workpiece, and it can be determined by using method 200. The predetermined property can be the predetermined thickness. As another example, the determined property can be the determined tool offset, and it can be determined by employing method 400. The predetermined property can be the predetermined tool offset. As another example, the determined property can be the determined offset factor, and it can be determined by using method 400. The predetermined property can be the predetermined offset factor. The determined property can be the presence or size of the panel gap. The predetermined property can be the predetermined presence or size of the panel gap. It should be understood that other determined properties can be compared with other predetermined properties.

[0226] The predetermined property can be the target value of the property. For example, the predetermined head height can be the target head height (i.e., the nominal value) of the fastener.

[0227] The predetermined property can be determined at any earlier time point. For example, the predetermined property can be loaded from a database. As an alternative example, the predetermined property can be determined based on the previous insertions of one or more fasteners.

[0228] The determined property can be based on multiple measurements. For example, the determined property can be the average of the determined head heights, with each determined head height corresponding to a different fastener. Each of the different fasteners can be located at the same point on the respective workpiece. In other words, the property of the joint on each workpiece can be determined and used to determine the average value. In other examples, the different fasteners can be located on the same workpiece.

[0229] Comparing the determined property with the predetermined property may include calculating the difference between the determined property and the predetermined property. The comparison may further include applying a threshold and / or dividing the difference by a factor. For example, by applying a threshold, the tool can determine that an adjustment is needed. The threshold may correspond to a tolerance. For example, if the head height of a fastener is expected to be 0.2 mm with a tolerance of 0.02 mm, the predetermined property may be 0.2 mm and the threshold may be 0.02 mm. Thus, if the fastener has been inserted with a head height greater than 0.22 mm or 0.18 mm, an adjustment can be determined and applied in steps 802 and 803, respectively.

[0230] The difference between the determined property and the predetermined property can indicate the condition of the fastener installation tool or the workpiece. The condition of the fastener installation tool can be or include temperature, lifespan, previous use of the tool, lubrication characteristics (such as amount of lubrication, temperature of the lubrication), etc. The condition of the workpiece can be or include the strength, ductility, or properties of the fastener.

[0231] In step 802, an adjustment is calculated. Generally, the adjustment can be for any characteristic on which the determined property depends. For example, if the determined property is the determined head height of a fastener, the adjustment can be for the torque or force applied by the fastener installation tool. As an alternative, the adjustment can be for the speed of the punch of the fastener installation tool.

[0232] The adjustment can be calculated to minimize the difference between the determined property and the predetermined property.

[0233] In some examples, the magnitude of the adjustment can be calculated based on the difference between the determined property and the predetermined property. In other words, the adjustment can be an increment (or decrement) of a specific value, regardless of how different the determined property is from the predetermined property. For example, if the fastener has a determined head height of 0.3 mm (and the predetermined head height is 0.2 mm with a tolerance of 0.02 mm), the tool can calculate that the torque applied by the fastener installation tool should be increased by 5 kN. For any determined head height above 0.22 mm, the same 5 kN increase can be calculated.

[0234] In other examples, the magnitude of the adjustment can be calculated based on the difference between the determined property and the predetermined property. In other words, the difference can be used to determine the adjustment. For example, when the predetermined head height is 0.2 mm, a greater adjustment can be applied to a determined head height of 0.5 mm compared to a determined head height of 0.3 mm.

[0235] In step 803, the adjustment is applied. In some examples, the adjustment can be applied automatically. That is, the fastener installation tool can apply the adjustment without any further input. In other examples, the method can further include outputting an indication of the adjustment at the output of the fastener installation tool. The method can further include receiving, at the input of the fastener installation tool, a user input indicating that the fastener installation tool is to apply the adjustment, and applying the adjustment in response to the user input. For example, the tool can determine that the adjustment should be applied and provide an indication to the user of the tool on a display. The user can indicate that the tool apply the adjustment based on an input via the display or a button.

[0236] In some examples, the adjustment can be applied after inserting the first fastener and before inserting the second fastener. In other words, the fastener installation tool can insert a first fastener with a first set of parameters and, based on a comparison, can insert a second fastener with a second set of parameters. In other examples, the adjustment can be applied after inserting the first fastener and before further inserting the first fastener. In other words, the fastener installation tool can insert a first fastener with a first set of parameters and, based on a comparison, can further insert a first fastener with a second set of parameters. In other words, the adjustment can be applied when inserting the first fastener.

[0237] As described above, method 800 can be iterative. As an example, each of the steps of method 800 can be repeated in sequence until it is determined that the property has changed (such that the result of the comparison between the determined property and the predetermined property is different). At this point, the tool can determine that no further adjustment is needed (similar to step 904 of method 900 described below). Alternatively, a second adjustment can be calculated and applied. The second adjustment can be an adjustment opposite to the most recently applied adjustment. In other words, the second adjustment can be opposite to the most recent adjustment and have the same magnitude as the most recent adjustment. For example, in the case where the most recent adjustment is to reduce the force applied to the tool to 2 kN, the second adjustment can increase the force applied to the tool by 2 kN. Advantageously, the tool can find the optimal parameters (at a given granularity level of the parameters) required to achieve a particular head height (or other parameter).

[0238] In addition, a third adjustment can be applied. The third adjustment can be opposite to the second adjustment (i.e., in the same direction as the first adjustment). The magnitude of the third adjustment can be less than the first adjustment. For example, the first adjustment can be +2 kN, the second adjustment can be -2 kN, and the third adjustment can be +0.5 kN. In this way, additional iterations of method 800 can be performed using steps of decreasing magnitude such that the optimal parameters (at an increasing granularity level of the parameters) required to achieve a particular head height (or other parameter) are obtained.

[0239] As an alternative to the second adjustment described above, the second adjustment can be opposite to the most recent first adjustment and have a smaller magnitude than the most recent first adjustment. For example, in the case where the most recent adjustment is to reduce the force applied to the tool to 2 kN, the second adjustment can increase the force applied to the tool by 0.5 kN. In other words, the first adjustment can be -2 kN and the second adjustment can be +0.5 kN. In this way, the method can continue until the magnitude of the adjustment matches the specific granularity of the tool that can be adjusted.

[0240] As an example of method 800, a rivet installation tool can insert a first fastener with a force of 85 kN to achieve a head height of 0.0 mm (i.e., the fastener can be flush). Thus, the tool can reduce the applied force by 2 kN. These steps can be repeated, and each subsequent fastener can be inserted with respective forces of 83 kN, 81 kN, 79 kN, and 77 kN, where each subsequent fastener has a head height of 0.0 mm. The force can be reduced to 75 kN, and the fastener inserted with this force can have a head height of 0.1 mm. The most recent adjustment can then be reversed, and then the tool can insert the fastener to a head height of 0.0 mm with 77 kN. In this way, the minimum force for inserting a fastener to a specific head height into a workpiece can be found.

[0241] The method can further include storing the determined parameters, predetermined parameters, adjustments, and / or determined parameters for subsequent fasteners. The stored values can be analyzed to determine or predict whether there are defects.

[0242] It should be understood that the steps of method 800 can be performed in any order. For example, method 800 can start with step 803 (applying an adjustment to a parameter).

[0243] Figure 9 is a flowchart depicting a method for determining that a fastener installation tool and / or workpiece does not need adjustment. In step 901, a determined attribute is compared with a predetermined attribute. In step 904, it is determined that no adjustment is needed.

[0244] The determined attribute can be compared with the predetermined attribute in a manner similar to that in method 800. In other words, step 901 can be performed in a manner similar to step 801.

[0245] In step 904, it is determined that no adjustment is needed. As discussed above in connection with step 801, comparing the determined attribute with the predetermined attribute can include applying a threshold to the difference. That is, if the difference is below the threshold, the tool can determine that no adjustment is needed.

[0246] Figure 10It is a flowchart depicting an iterative method 1000 for calculating adjustments and applying the adjustments to a fastener installation tool and / or a workpiece. The iterative method 1000 is an example of how to perform methods 800 and 900 iteratively.

[0247] In step 1011, a first determined property is compared with a first predetermined property. In step 1012, a first adjustment is calculated. In step 1013, the first adjustment is applied. In step 1021, a second determined property is compared with a second predetermined property. In step 1022, it is determined what kind of second adjustment is needed. In step 1023, the second adjustment is applied. Alternatively, in step 1024, the second adjustment is not applied.

[0248] Each step of the iterative method 1000 can be performed in a manner similar to the corresponding steps of methods 800 and 900. Determining what kind of second adjustment is needed (i.e., step 1022) can be performed in a manner similar to calculating an adjustment in step 802 and / or determining that no adjustment is needed in step 904. That is, if the difference between the second determined property and the second predetermined property is below a threshold, the second adjustment may not be applied. Alternatively, if the difference between the second determined property and the second predetermined property is above a threshold, the second adjustment may be applied. The magnitude of the second adjustment may depend on the difference, as discussed above with respect to method 800. Alternatively, the magnitude of the second adjustment may be independent of the difference.

[0249] It should be understood that the use of "first" and "second" in relation to method 1000 is a label. In other words, there can be any number of first adjustments.

[0250] Although terms such as "downward" or "top" are used in this specification, it should be understood that these terms are exemplary and do not imply that any specific orientation of the device is necessary. For example, when Figure 1 the rivet installation tool 2 depicted in is operating on a workpiece W that is substantially flat and aligned with a horizontal plane, the rivet installation tool 2 can operate on the workpiece W aligned in another way.

[0251] It should be understood that the threshold tests (and corresponding actions) described herein (i.e., those described with respect to method 200, method 400, and method 500) are merely exemplary, and other combinations (including other threshold tests on other determined values) may be advantageous.

[0252] Although the steps of the methods (i.e., method 200, method 400, etc.) described herein have been described in sequence, this sequence is not a requirement of the present invention. For example, in method 200, the position of the calibration location (in step 202) can be measured after the position of the surface of the workpiece 330 has been measured (in step 204).

[0253] Although the steps of the methods described herein have been described as being performed, one or more of the methods may be implemented as computer-implemented methods. For example, one or more of the methods may be stored on a computer-readable storage medium that, when read by a computer, causes a fastener installation tool 310 controlled by the computer to perform one or more of the methods. The computer may be referred to as a controller. It should be understood that, in a computer-implemented method, an action may be (instead of being performed) described as being caused to be performed. For example, in method 200, step 201 is to advance a blank holder to a calibration position. In a computer-implemented method, the corresponding step may be to cause the blank holder to advance to the calibration position.

[0254] It should be understood that a reference to any of the following: receiving a quantity; determining a quantity; and measuring a quantity may be interpreted in the same way. For example, receiving a determined position of a top surface of a fastener may include determining and / or measuring the position of the top surface of the fastener.

[0255] It should also be understood that a reference to the energy applied by a rivet insertion tool to a fastener may equally refer to the force applied by the rivet insertion tool to the fastener. It is well known that some rivet insertion tools operate by applying torque. A reference to the energy (applied by the rivet insertion tool) may equally refer to the corresponding torque. It should also be understood that a force sensor may alternatively be referred to as an energy sensor or a torque sensor (and vice versa).

[0256] Figure 11 An exemplary computer system 1100 is shown. The computer-implemented method 100 (or any other method described herein) may be implemented on a computer system such as computer system 1100. Computer system 1100 may include a central processing unit 1110, a memory 1120, one or more storage devices 1130, an input / output processor 1140, circuitry for connecting components 1050, and one or more input / output devices 1160.

[0257] This specification uses the term "configured" in connection with systems and computer program components. For a system of one or more computers configured to perform particular operations or actions, it means that the system has installed thereon software, firmware, hardware, or a combination thereof that, in operation, causes the system to perform the operations or actions. For one or more computer programs configured to perform particular operations or actions, it means that the one or more programs include instructions that, when executed by a data processor, cause the device to perform the operations or actions.

[0258] Embodiments of the subject matter and the functional operations described in this specification can be implemented in digital electronic circuitry, in tangibly implemented computer software or firmware, in computer hardware including the structures disclosed in this specification and their structural equivalents, or in combinations of one or more of them. Embodiments of the subject matter described in this specification can be implemented as one or more computer programs, i.e., one or more modules of computer program instructions encoded on a tangible non-transitory storage medium for execution by, or to control the operation of, a data processing apparatus. A computer storage medium may be a machine-readable storage device, a machine-readable storage substrate, a random or serial access storage device, or a combination of one or more of them. Alternatively or additionally, the program instructions may be encoded on an artificially generated propagated signal (e.g., a machine-generated electrical, optical, or electromagnetic signal) that is generated to encode information for transmission to the appropriate receiver device for execution by the data processing apparatus.

[0259] The term “data processing apparatus” refers to data processing hardware and encompasses all types of devices, apparatus, and machines for processing data, including, by way of example, a programmable processor, a computer, or multiple processors or computers. The apparatus may also be, or further include, special purpose logic circuitry, such as an FPGA (field programmable gate array) or an ASIC (application specific integrated circuit). In addition to hardware, the apparatus may optionally include code that creates an execution environment for the computer program, e.g., code that constitutes processor firmware, a protocol stack, a database management system, an operating system, or a combination of one or more of them.

[0260] A computer program, which may also be referred to as or described as a program, software, a software application, an app, a module, a software module, a script, or code, can be written in any form of programming language, including a compiled or interpreted language, or a declarative or procedural language; and it can be deployed in any form, including as a stand-alone program or as a module, a component, a subroutine, or other unit suitable for use in a computing environment. A program may, but need not, correspond to a file in a file system. A program may be stored in a portion of a file that holds other programs or data, such as one or more scripts in a markup language document, in a single file dedicated to the program being discussed, or in multiple coordinated files, such as files that store one or more modules, subroutines, or portions of code. A computer program may be deployed to execute on one computer or on multiple computers located at one site or distributed across multiple sites and interconnected by a data communication network.

[0261] The processes and logical flows described in this specification can be performed by one or more programmable computers that execute one or more computer programs to perform functions by operating on input data and generating output. The processes and logical flows can also be performed by, or by a combination of, special purpose logic circuitry, such as an FPGA or ASIC, or special purpose logic circuitry and one or more programmed computers.

[0262] Computers suitable for executing computer programs can be based on general or special purpose microprocessors or both, or any other type of central processing unit. In general, a central processing unit will receive instructions and data from a read only memory or a random access memory or both. The basic elements of a computer are a central processing unit for performing or executing instructions and one or more storage devices for storing instructions and data. The central processing unit and the memory can be supplemented by, or incorporated in, special purpose logic circuitry. In general, a computer will also include one or more mass storage devices for storing data, such as magnetic disks, magneto-optical disks, or optical disks, or operatively coupled to receive data from or transfer data to one or more mass storage devices for storing data, or both. However, a computer need not have such devices. In addition, a computer can be embedded in another device, such as a mobile telephone, a personal digital assistant (PDA), a mobile audio or video player, a game console, a global positioning system (GPS) receiver, or a portable storage device, such as a universal serial bus (USB) flash drive, to name just a few.

[0263] Computer-readable media suitable for storing computer program instructions and data include all forms of non-volatile memory, media, and memory devices, including semiconductor storage devices, such as EPROM, EEPROM, and flash memory devices; magnetic disks, such as internal hard disks or removable disks; magneto-optical disks; and CD-ROM and DVD-ROM disks.

[0264] To provide for interaction with a user, embodiments of the subject matter described in this specification may be implemented on a computer having a display device (e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor) for displaying information to the user and a keyboard and a pointing device (e.g., a mouse or a trackball) by which the user may provide input to the computer. Other kinds of devices may also be used to provide for interaction with the user; for example, the feedback provided to the user may be any form of sensory feedback, such as, visual feedback, auditory feedback, or tactile feedback; and input from the user may be received in any form, including acoustic, speech, or tactile input. Additionally, the computer may interact with the user by sending documents to and receiving documents from the devices used by the user; for example, by sending a web page to a web browser on the user's device in response to a request received from the web browser. Further, the computer may interact with the user by sending text messages or other forms of messages to a personal device (e.g., a smart phone running a messaging application) and receiving a response message in return from the user.

[0265] The data processing device for implementing a machine learning model may also include, for example, a dedicated hardware accelerator unit for processing common and computationally intensive portions of machine learning training or generation (i.e., inference) workloads.

[0266] A machine learning framework (e.g., TensorFlow framework, Microsoft Cognitive Toolkit framework, Apache Singa framework, or Apache MXNet framework) may be used to implement and deploy a machine learning model.

[0267] Embodiments of the subject matter described in this specification may be implemented in a computing system that includes a backend component (e.g., as a data server), or includes a middleware component (e.g., an application server), or includes a frontend component (e.g., a client computer having a graphical user interface, a web browser, or an application through which a user may interact with the subject matter described in this specification), or any combination of one or more such backend, middleware, or frontend components. The components of the system may be interconnected by any form or medium of digital data communication (e.g., a communication network). Examples of communication networks include a local area network (LAN) and a wide area network (WAN), such as the Internet.

[0268] A computing system may include a client and a server. The client and the server are typically remote from each other and typically interact via a communication network. The relationship between the client and the server arises by virtue of computer programs running on respective computers and having a client-server relationship with each other. In some embodiments, the server transmits data (e.g., an HTML page) to a user device, e.g., for the purpose of displaying data to and receiving user input from a user interacting with the device acting as the client. Data generated at the user device (e.g., results of user interactions) may be received at the server from the device.

[0269] Although this specification contains many specific implementation details, these should not be construed as limitations on the scope of any invention or of what may be claimed, but rather as descriptions of features specific to particular embodiments of a particular invention. Certain features that are described in this specification in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment may also be implemented separately or in any suitable sub-combination in multiple embodiments. Additionally, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination may in some cases be excised from the combination, and the claimed combination may be directed to a sub-combination or variation of a sub-combination.

[0270] Similarly, although operations are depicted in the drawings in a particular order and recited in the claims, this should not be understood as requiring that such operations be performed in the particular order shown or in a sequential order, or that all illustrated operations be performed to achieve a desired result. In some cases, multitasking and parallel processing may be advantageous. Additionally, the separation of various system modules and components in the above-described embodiments should not be understood as required in all embodiments, and it should be understood that the described program components and systems may generally be integrated together in a single software product or packaged into multiple software products.

[0271] Particular embodiments of the subject matter have been described. Other embodiments are within the scope of the appended claims. For example, the acts recited in the claims may be performed in a different order and still achieve the desired result. As one example, the processes depicted in the drawings do not necessarily need the particular order or sequential order shown to achieve the desired result. In some cases, multitasking and parallel processing may be advantageous.

Claims

1. A computer-implemented method for determining properties of a fastener, the method comprises: receiving a stored offset factor that correlates an offset of a fastener installation tool with a peak force applied by the fastener to a die; receiving a determined peak force that corresponds to the peak force applied by a punch of the fastener installation tool to the fastener; receiving a determined thickness of a workpiece; receiving a determined position of a top surface of the fastener; and determining a head height HH of the fastener as: HH = (DF × PF) - MT + ED wherein, DF is the stored offset factor; PF is the determined peak force; MT is the determined thickness of the workpiece; and ED is the determined position of the top surface of the fastener.

2. The method according to claim 1, wherein, receiving the determined thickness of the workpiece further comprises: advancing a blank holder of the fastener installation tool such that the blank holder moves to a calibration position; measuring a position of the calibration position along an axis traveled by the blank holder using a first sensor configured to measure displacement of the blank holder; advancing the blank holder such that the blank holder contacts a surface of the workpiece and clamps the workpiece against the die; measuring a position of the surface of the workpiece along the axis traveled by the blank holder using the first sensor; and determining the thickness of the workpiece using the measured position of the calibration position and the measured position of the surface of the workpiece.

3. The method according to claim 1 or 2, further comprises: applying a threshold test to the determined head height.

4. A computer-implemented method for determining properties of a workpiece and / or a fastener installation tool, the method comprises: advancing a blank holder of the fastener installation tool such that the blank holder moves to a calibration position; measuring a position of the calibration position along an axis traveled by the blank holder using a first sensor configured to measure displacement of the blank holder; advancing the blank holder such that the blank holder contacts a surface of the workpiece and clamps the workpiece against a die; measuring a position of the surface of the workpiece using the first sensor; determining the thickness of the workpiece using the measured position of the calibration position and the measured position of the surface of the workpiece.

5. The method according to claim 4, further comprises: receiving a determined position of a top surface of the fastener; receiving a measured head height of the fastener; determining a tool offset TD corresponding to a change in an end position of a component of the tool relative to a starting position due to insertion of the fastener as: TD = HH + MT - ED wherein, HH is the measured head height of the fastener; MT is the determined thickness of the workpiece; and ED is the determined position of the top surface of the fastener.

6. The method according to claim 5, further comprises storing the determined tool offset.

7. The method according to claim 5 or 6, further comprising: determining a peak force applied by the punch to the fastener; and determining an offset factor DF corresponding to the offset of the fastener installation tool relative to the peak force applied by the punch to the fastener as: DF = TD ÷ PF where PF is the determined peak force.

8. The method according to claim 7, further comprising storing the offset factor.

9. The method according to any one of claims 4 to 8, further comprising applying a threshold test to the determined attribute.

10. A method implemented by a computer for determining an attribute of a workpiece or an attribute of a joint made at the workpiece, the method comprising: bringing a blank holder of a fastener installation tool into contact with the surface of the workpiece; applying a force along the axial direction of the blank holder towards the workpiece to the blank holder; detecting movement of the workpiece by measuring displacement of the blank holder; and determining the attribute of the workpiece or the attribute of the joint made at the workpiece based on the detected movement.

11. The method according to claim 10, further comprising applying a threshold test to the determined attribute.

12. The method according to any one of the preceding claims, further comprising: inserting a first fastener into the workpiece by a punch of the fastener installation tool.

13. The method according to any one of claims 3, 9, or 11, further comprising: determining that the fastener installation tool needs maintenance based on the result of the threshold test.

14. The method according to any one of claims 3, 9, 11, or 13, further comprising: determining that the workpiece should be inspected and / or replaced based on the result of the threshold test.

15. The method according to any one of claims 3, 9, 11, 13, or 14, further comprising: determining that a parameter associated with the fastener installation tool should be adjusted based on the result of the threshold test.

16. The method according to any one of claims 2 to 15, wherein measuring the displacement of the blank holder comprises: measuring the displacement of a member of the fastener installation tool fixed relative to the blank holder.

17. The method according to any one of the preceding claims, further comprising: comparing the determined attribute with a predetermined attribute, wherein the difference between the determined attribute and the predetermined attribute represents the condition of the fastener installation tool or the workpiece; calculating an adjustment based on the comparison to compensate for the condition of the fastener installation tool or the workpiece; and applying the adjustment to the fastener installation tool and / or the workpiece.

18. The method according to claim 17, which depends on claim 12, wherein comparing the determined attribute with the predetermined attribute, calculating an adjustment based on the comparison, and making the adjustment respectively after the punch has inserted the first fastener into the workpiece; where the method further comprises, after the adjustment has been applied: inserting a second fastener into the workpiece by the punch.

19. The method according to claim 17, dependent on claim 12, wherein, the determined attribute is compared with the predetermined attribute, an adjustment is calculated based on the comparison, and after the punch has inserted the first fastener into the workpiece, the adjustment is made respectively; where the method further comprises, after the adjustment has been applied: causing the punch to further insert the first fastener into the workpiece.

20. The method according to any one of claims 17 to 19, wherein: the adjustment is an adjustment of the torque and / or force applied by the fastener installation tool.

21. The method according to any one of claims 17 to 19, wherein: the adjustment is an adjustment of the speed of the fastener installation tool.

22. The method according to any one of claims 1 to 16, further comprising: comparing the determined attribute with a predetermined attribute, wherein the difference between the determined attribute and the predetermined attribute represents the condition of the fastener installation tool and / or the workpiece; and determining, based on the comparison, that no adjustment to the fastener installation tool and / or the workpiece is required.

23. The method according to any one of claims 17 to 22, dependent on claim 1, wherein: the determined attribute is the determined head height of the first fastener; and the predetermined attribute is a predetermined head height.

24. The method according to any one of claims 17 to 22, dependent on claim 4, wherein: the determined attribute is the determined thickness of the workpiece; and the predetermined attribute is a predetermined thickness.

25. The method according to any one of claims 17 to 22, dependent on claim 5, wherein: the determined attribute is a determined tool offset; and the predetermined attribute is a predetermined tool offset.

26. The method according to any one of claims 17 to 22, dependent on claim 7, wherein: the determined attribute is a determined offset factor; and the predetermined attribute is a predetermined offset factor.

27. A method implemented by a computer for determining the force for inserting a fastener into a workpiece using a fastener installation tool, the method comprises: receiving the required head height of the fastener; receiving the thickness of the workpiece; receiving an offset factor; receiving the desired position of the top surface of the fastener; determining the force PF applied to the fastener by the punch of the fastener installation tool as: where: HH is the required head height of the fastener; DF is the offset factor; MT is the thickness of the workpiece; and ED is the position of the top surface of the fastener.

28. A fastener installation tool configured for use in the method according to any one of the preceding claims.

29. A controller for a fastener installation tool, wherein, the controller is configured to execute the method according to any one of claims 1 to 27.

30. A fastener installation tool comprising a first sensor configured to measure the displacement of a blank holder.

31. The fastener installation tool according to claim 30, further comprising a member that is fixed relative to the blank holder, and wherein, the first sensor is configured to measure the displacement of the member.

32. The fastener installation tool according to claim 30 or 31, wherein, the first sensor is a contact displacement sensor.

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