CN117798308A - Numerical control riveting system based on variable data chain - Google Patents
Numerical control riveting system based on variable data chain Download PDFInfo
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Abstract
The scheme discloses a numerical control riveting system based on variable data chains, which is used for connecting a riveting power mechanism, wherein the numerical control riveting system is used for setting a coordinate origin of riveting process parameter variables based on a riveting fastener applying process in a riveting process, constructing a coordinate reference system among the riveting process parameter variables, marking the riveting process parameter variables obtained in the riveting process in the coordinate reference system to obtain variable data chains composed of the riveting process parameter variables, and then performing riveting control and/or riveting diagnosis by the numerical control riveting system according to the characteristics of the variable data chains. Based on the variable data chain, setting a coordinate origin in the riveting process, constructing a coordinate reference system of variable data, searching key points of the variable data chain in the coordinate reference system, and controlling and diagnosing riveting based on the key points, so that the riveting precision and the riveting quality can be improved, and the consistency of the riveting quality can be ensured.
Description
Technical Field
The invention belongs to the technical field of riveting, and particularly relates to a numerical control riveting system based on a variable data chain.
Background
The rivet is used as a cold riveting technology, a rivet fastener and a rivet workpiece are required to be riveted by using rivet tools or equipment, the tensile strength and the shearing resistance of the rivet fastener are higher than those of fastening technologies such as spot welding, the relative cost is lower, the connection quality is higher, the replacement of gluing, welding and bolting is realized in various fields, the rivet is widely applied to various industries involving national and civil life including aviation, aerospace, military industry, ships, high-speed rails, automobiles, buildings, installation, production and the like, and a large amount of personal application demands are also provided in the civil field. Meanwhile, along with the increase of economy, the thin plate piece has increasingly wide application, the market of riveting fasteners and corresponding riveting tools and equipment related industries which can process the connection of the thin plate piece is continuously moving high, and the demand of various riveting tools and equipment is increased year by year. Rivet nuts are also called blind rivet nuts, blind caps, threaded blind rivets and the like, screw connection is provided while riveting workpieces are fastened, the proportion of the blind rivet type rivet fastening pieces is increasingly enlarged, materials from aluminum to all steel and all stainless steel are changed from low strength to high strength, a series of standard products with various specifications and models are formed, and corresponding blind rivet tools and equipment are continuously developed towards the directions of multifunction, precision heavy load, portability, labor saving, easiness in use, high automation and high cost performance.
In the existing riveting nut pulling and riveting tools and devices, the traditional manual riveting tool (such as US20140033492 A1) designed based on the lever principle is laborious to operate and has low efficiency. As a solution of replacing a power source, a pulling rivet tool and equipment using pneumatic and hydraulic as power sources have been developed and popularized to a certain extent, but the application range is affected due to the need of additionally providing compressed air or a hydraulic pump station, and the problems of high cost and energy efficiency are also affected, so that the pulling rivet tool and equipment are applied to the industrial market. In consideration of fluctuation of the pressure of compressed air and the hydraulic oil pressure, the out-of-control riveting force often causes poor riveting precision and easily causes structural impact damage to a riveting workpiece, particularly a thin plate member, so that the quality defect of riveting is difficult to control. Therefore, in recent years, the research and development of the riveting industry in the global scope is focused on turning to electric riveting tools and equipment, and novel electric riveting technology is continuously emerging.
It is worth noting that the riveting tool driven by manual to pneumatic, hydraulic, electric or other driving tools solves the problem of a power source more so as to replace manpower and improve the riveting work efficiency. The handling of the power riveting tools for the riveting process is still largely dependent on man. As shown in fig. 1, for the rivet nut, it is necessary to continuously apply a rivet force so that a ductile region or a thin-walled deformed region is plastically deformed, upset and further form a "upset head" to tighten the rivet workpiece. As shown in fig. 2 (a), the fastening effect on the riveted workpiece in the manual mode depends on the operation hand feeling of the user for riveting the fastener with different materials and specifications and the observation of the "upsetting", and is shielded by the riveted workpiece, so that the user is more blind in riveting, and the riveting problems such as under riveting, over riveting, damage of the riveted thread pair and the like are easily caused due to the influences of the thickness, the material, the aperture size and the like of the riveted workpiece.
In order to reduce the dependence on individual control experience and realize automatic blind riveting, the power problem is solved, and a control method for keeping the riveting quality consistency under the riveting fasteners with different materials and different specifications is needed. For this reason, as shown in fig. 2 (b), there is a control method for realizing blind riveting by adjusting a riveting stroke, that is, a compression stroke of a preset fixed value completes blind riveting by adjusting a riveting tightening stroke of a blind riveting tool according to the specification of a rivet nut and the thickness of a rivet workpiece. However, considering the influence of factors such as technology, the thickness of the actual riveted workpiece is not completely equal to the theoretical value, and the problems of deformation of the riveted workpiece, especially the thin plate, can occur, which also causes the riveting problems such as under riveting/over riveting. In order to avoid the risk, accurate values of the thickness of the riveted workpiece are often required to be obtained one by one before riveting, and the standard rivet pulling stroke is calculated according to the accurate values so as to ensure the consistency of the final riveting quality, and the operation becomes very complicated.
Related researches show that the technological parameters affecting the riveting quality, including the material and specification of the riveting fastener, the dimensional tolerance of the material and the mounting aperture of the riveting workpiece, the riveting force and the like, all affect the formation of an upsetting head in the riveting process. The formation of the "upset" requires that sufficient axial load be imparted to the rivet nut to achieve full plastic deformation of its malleable region or thin walled deformed region. The control of the riveting force through the riveting process is also one of the important technical routes for realizing automatic blind riveting. The difference of the specification and the model of the rivet nut can be twice, which means that the required riveting Force (riveting Force) in the process of riveting has obvious difference and changes with the different materials, specifications and structures of the rivet nut. In the process of riveting, the riveting force is automatically controlled, and the specification and model of the riveting nut are required to be obtained in advance to obtain the proper riveting force. Considering that the direct identification of the specification and the model of the riveting nut is difficult, the selection/input by a user can be considered, the process is complicated, the insufficient riveting force or overload can be caused when the selection/input is wrong, and the riveting problems such as under riveting/over riveting and the like can be possibly caused.
Disclosure of Invention
The invention aims to solve the problems and provide a numerical control riveting system and a control method.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
a numerical control riveting system based on variable data chains is used for connecting a riveting power mechanism, the numerical control riveting system is used for setting the coordinate origin of riveting process parameter variables based on riveting fastener riveting process in the riveting process, constructing a coordinate reference system among the riveting process parameter variables, marking the riveting process parameter variables obtained in the riveting process in the coordinate reference system to obtain variable data chains composed of all the riveting process parameter variables, and then performing riveting control and/or riveting diagnosis by the numerical control riveting system according to the characteristics of the variable data chains.
In the numerical control riveting system based on the variable data chain, the riveting process parameter variable comprises a riveting force, and the coordinate reference system comprises a riveting force-time coordinate system;
or, the parameter variables comprise riveting force and riveting stroke, and the coordinate reference system comprises any one or more of a riveting force-time coordinate system, a riveting force-riveting stroke coordinate system, a riveting stroke-time coordinate system or a riveting force-riveting time-riveting stroke coordinate system;
And correspondingly, the variable data chain comprises any one or more of a variable point set of riveting force changing along with time, a variable point set of riveting force changing along with riveting stroke, a variable point set of riveting stroke changing along with time, or a variable point set of riveting force and riveting stroke along with time.
In the above-described numerical control caulking system based on a variable data chain, the origin of coordinates 0 of the caulking process parameter variable as the coordinate reference system variable cluster is set as follows:
setting an origin 0 of a riveting process parameter variable riveting Force by taking an origin of an effective Shi Mao load as a reference origin, wherein a measured value of a riveting Force sensor increases linearly in the same direction along with the increase of a riveting load from 0, and the reading of the riveting Force sensor returns to 0 when the Shi Mao load is completely unloaded, wherein the minimum measured value of the riveting Force sensor is 0;
setting an origin 0 of a riveting process parameter variable riveting Stroke by taking an origin of an effective Shi Mao load as a reference origin, wherein the measured value of a riveting Stroke sensor linearly changes in the same direction along with the axial displacement (rotation angle) of a transmission system, and the riveting Stroke can be a negative value and is used for representing a reverse withdrawal Stroke;
setting an origin 0 of riveting process parameter variable riveting time t by taking the origin of an effective Shi Mao load as a reference origin, wherein the time t is a natural variable;
The rivet force is equal to the pretension threshold and is considered the starting point for the effective Shi Mao load.
In the numerical control riveting system based on the variable data chain, the numerical control riveting system tracks and analyzes the riveting process parameter variable of the space vector, and acquires at least one characteristic point to perform riveting control and/or riveting diagnosis according to the characteristic point;
the characteristic points comprise any one or more of an elastic-plastic conversion point Datum, a riveting starting point Fs, a second entity point Pier, a riveting force peak point Fmax, a rebound unloading point Fr and a Shi Mao end point Fe;
the numerical control riveting system divides the standard riveting process into three or four typical stages by identifying each characteristic point of the riveting process, a Forming stage, a Yielding stage, a Setting stage and a fourth typical stage restination stage, wherein:
forming stage corresponds to self-riveting starting point F s The section reaching the elastic-plastic conversion point Datum is the elastic deformation stage of the riveting fastener under the load;
the YIelding stage corresponds to a section from an elastic-plastic conversion point Datum to a second entity point Pier, and is a plastic deformation upsetting stage of the riveting fastener under the effect of riveting load and constrained by the wall of a hole of a riveting workpiece;
the Setting stage corresponds to the second entity point from Pier to the riveting force peak point F max The section is a plastic deformation upsetting head-second entity upsetting head Preform forming stage of the riveting fastener under the effect of riveting load and constrained by the wall of the hole of the riveting workpiece and the contact surface of the upsetting head;
the response stage corresponds to the riveting force peak point F max To rebound unloading point F r A section, an optimized forming stage for maintaining Shi Mao load of the rivet fastener to eliminate residual stress effects.
In the numerical control riveting system based on the variable data chain, the riveting control performed by the numerical control riveting system according to the characteristics of the variable data chain comprises riveting control in any one or more combination modes of a Dummy test mode, a Parametric Riveting parameter mode, a Adaptive Riveting self-adaptive mode and a Resume riveting mode;
the riveting diagnosis performed by the numerical control riveting system according to the characteristics of the variable data chain comprises any one or more of a Process diagnosis mode, a Quality diagnosis mode, a Rivet diagnosis mode and a Workpiece diagnosis mode.
In the above numerical control riveting system based on variable data chain, the control process in Parametric Riveting parameter mode is as follows:
SA1, presetting a stop point riveting force peak value Fmax according to an input riveting nut specification material; the maximum riveting stroke threshold Smax can be set in the upper limit range and the lower limit range of the preset riveting force peak Fmax meeting the riveting requirement, and the actual use is mainly used for adjusting the riveting force peak Fmax in consideration of the tiny adjustable range of the maximum actual riveting stroke threshold Smax;
SA2, uploading a riveting fastener, starting a power unit of a riveting power mechanism to pretighten the riveting fastener, and monitoring whether the axial force is higher than a pretightening force threshold value in real time by a numerical control riveting system, and setting a coordinate origin to construct a coordinate reference system when the axial force reaches the pretightening force threshold value;
SA3, applying a load by the numerical control riveting system to enter a riveting stroke, monitoring the riveting force or the riveting force and the riveting stroke in real time, and generating a value monitored in real time as a variable cluster of a coordinate reference system to the coordinate reference system;
SA4, monitoring parameter variables of a riveting process in a coordinate reference system, obtaining an elastic-plastic conversion point Datum, comparing the parameter variables with a pre-stored Datum range corresponding to a riveting nut specification material as a riveting process diagnosis reference point, giving a prompt if the Datum exceeds the range, simultaneously automatically switching to an adaptive mode to continue riveting control, and otherwise continuing to execute SA5; indicating error in specification input of rivet nut
SA5 monitoring whether the riveting force in the coordinate reference system reaches the peak value F of the riveting force at the stop point max If yes, automatically cutting off the power supply to finish the riveting action according to the preset, or automatically cutting off the power supply to finish the riveting action after the riveting force is kept for a period of time;
The system pre-stores riveting process functions f (-) corresponding to the riveting nuts of all specifications, the riveting process functions f (-) comprise variable data chains, and in step SA1, corresponding f (-) is obtained based on riveting nut specification materials, so that the riveting force peak value Fmax is determined.
In the above numerical control riveting system based on variable data chain, the control process of the Adaptive Riveting adaptive mode is as follows:
the method comprises the steps of SB1, uploading a riveting fastener, starting a power unit of a riveting power mechanism to pretighten the riveting fastener, and setting a coordinate origin to construct a coordinate reference system when a numerical control riveting system monitors whether an axial force is higher than a pretightening force threshold value in real time and reaches the pretightening force threshold value;
SB2, applying a load to enter a riveting stroke by the numerical control riveting system, monitoring the riveting force or the riveting force and the riveting stroke in real time, and generating a value monitored in real time as a variable cluster of a coordinate reference system to the coordinate reference system;
SB3 monitoring the riveting process parameter variable in the coordinate reference system and obtaining an elastic-plastic conversion point Datum, taking the parameter variable as a control reference point, and calculating a riveting force peak value F of the self-adaptive stopping point according to the control reference point Datum max ；
SB4 monitoring parameter variables of riveting process in the coordinate reference system and obtaining a second entity point Pier, indicating to enter a Setting stage after the second entity point Pier is monitored, and when the real-time riveting force reaches a riveting force peak value F max Step SB5 is executed;
SB5, the numerical control riveting system selects to automatically cut off a power supply to finish the riveting action according to the preset, or enters a reporting stage, monitors time and riveting force, controls the riveting force to gradually drop to zero along the set time to cut off the power supply of the motor to finish the riveting action, or keeps the riveting force at the reporting stage to cut off the power supply of the motor to finish the riveting action after the riveting force threshold value reaches the set time;
when the offset is preset, the offset is based on the riveting force peak value F according to the preset experience max Determining an adjustable range of a riveting force threshold value, and executing step SB5 based on the riveting force adjustable range;
the system is pre-stored with a riveting process function F (-) corresponding to each specification of riveting nut, the riveting process function F (-) comprises the variable data chain, and in step SB3, datum and a riveting force peak value F are determined based on an elastic-plastic conversion point Datum max And calculates the riveting force peak value Fmax according to the functional relation and Datum. Datum is a characteristic point directly related to the individual riveting fastener, and a specific function relation of each Datum optimal and riveting force peak value Fmax is prestored in the system, wherein the specific function is obtained through idle test of the corresponding riveting nut in advance, and in the function relation, datum is taken as input, fmax is taken as output, for example fmax=1.2 Datum. Each of these may have subtle variations due to interference from measurements or other factors, even if Datum is obtained at different times on the same rivet nut The Datum has an adaptation range, and the Datum in the adaptation range is regarded as the same Datum, if the adaptation range of a certain Datum is 14050N-13950N, and about 1300um-1500um, the point in the range belongs to the Datum, and if the current Datum point is (1305,14025), the riveting force peak Fmax is calculated according to 14025.
The current riveting process function f (·) comprises a riveting process parameter variable point set in the current riveting process;
a plurality of riveting process functions f (-) corresponding to various specifications of riveting nuts one by one are prestored in the system, and each riveting process function f (-) comprises a riveting process parameter variable point set in the riveting process of the corresponding type of riveting nut;
in the numerical control riveting system based on the variable data chain, the Dummy test mode is used for blank drawing tests under the working condition that the uploading riveting fastener is not loaded with a riveting workpiece, a specific function relation between the corresponding riveting nut and the optimal riveting force peak value of the corresponding riveting nut can be obtained through a plurality of blank drawing tests, and a riveting process function f (&) of the corresponding riveting nut can be obtained as a reference;
the Resume continuous riveting mode is a strong withdrawal continuous riveting mode under the abnormal interruption working condition in the riveting process, a numerical control riveting system acquires riveting characteristic points in the riveting working process, determines the riveting stage and the forward fastening stroke where the abnormal interruption is located, and provides strong withdrawal protection and continuous riveting control according to the abnormal interruption working condition;
The strong backing protection is that when an abnormal interrupt user forcedly exits, the numerical control riveting system stores interrupt field data, monitors and confirms that the voltage/current of a motor in an exiting stroke is within a permissible range in real time, ensures that the reverse stroke is larger than the sum of the corresponding strokes of the forward fastening stroke and the protection turns, ensures that gap separation exists between the riveting nut and the guide nozzle, and enables the pull rod to continue to exit and be in threaded connection with the riveting nut;
the continuous riveting control is a mortise applying operation which is performed again after the forced withdrawal of the abnormal interruption occurs, and the numerical control riveting system controls the continuous riveting operation according to the interruption position, wherein the continuous riveting operation comprises a continuous riveting operation of the abnormal interruption in a Forming stage, a continuous riveting operation of the abnormal interruption in a YIelding stage and a continuous riveting operation of the abnormal interruption in a Setting stage.
In the above-mentioned numerical control riveting system based on variable data chain, the Process diagnosis mode diagnosis Process is as follows:
generating a current riveting process function f '(. Cndot.) in the riveting process, and judging whether a remarkable abnormality exists in the riveting process or not based on a pre-stored riveting process function f' (. Cndot.) and a preset allowable deviation amount Bias thereof according to the consistency of the characteristic vector and/or the change rule of the pre-stored riveting process function f (& cndot.) in the riveting process;
Or generating and outputting a riveting characteristic curve which is smoothly subjected to riveting process parameter variables according to the set coordinate origin, standardizing the riveting characteristic curve, comparing and analyzing the riveting characteristic curve with a riveting reference characteristic curve, and using the riveting characteristic vector distance as a similarity representation for judging whether obvious abnormality exists in the riveting process;
or acquiring a riveting characteristic vector, and diagnosing the riveting process by using any one or combination of a plurality of concentrated, off-center, off-state and peak characteristic values based on a statistical analysis method of historical data, wherein the method comprises abnormality detection based on process statistics 6 sigma and/or Box Plot (Box graph) and is used for judging whether obvious abnormality exists in the riveting process; the historical data can be data in the system test process or data in the early use process;
the pre-stored riveting process function f (,), the riveting reference characteristic curve are obtained through a Dummy test mode of riveting nuts delivered from a batch, or are obtained through a Dummy test mode of one or more riveting nuts in the same batch;
a Quality diagnosis mode, wherein a current riveting process function f' (. Cndot.) is obtained in the riveting work process, a pre-stored corresponding riveting process function f (-) is obtained based on the characteristic points, and whether the riveting Quality problem caused by under riveting/over riveting exists is judged according to the comparison of the two riveting process functions;
The Quality diagnosis mode is also used for judging whether abnormal riveting Process affecting the riveting Quality exists or not through the diagnosis of the riveting working Process on the basis of the Process diagnosis mode;
the diagnostic procedure for the Rivet diagnostic mode is as follows: acquiring a riveting characteristic vector in the riveting process, and judging whether a deviation exists between the riveting characteristic vector and a riveting fastener selected/input by a user or whether the riveting fastener has a significant difference in the riveting process in the same batch based on the material and the specification of the riveting fastener represented by the individual elastic-plastic conversion point of the Datum riveting nut, so as to be used for material mixing diagnosis;
the diagnostic procedure for the Workpiece diagnostic mode is as follows: and acquiring a riveting characteristic vector in the riveting process, and judging whether the thickness of the riveting workpiece exceeds a permissible threshold range or not or whether the thickness of the riveting workpiece has obvious difference in the same batch of riveting work based on the thickness of the riveting workpiece represented by the Datum elastic-plastic conversion point and the Pier second entity point.
In the numerical control riveting system based on the variable data chain, the numerical control riveting system generates and outputs a riveting characteristic curve smoothly passing through the riveting process parameter variable according to the set coordinate origin based on the coordinate reference system, the riveting characteristic curve describes the association relation among the riveting process parameter variables in the coordinate reference system, the numerical control riveting system identifies each characteristic point by analyzing the riveting characteristic curve, performs riveting control and/or riveting diagnosis based on the riveting characteristic curve, and divides the standard riveting process into four typical stages based on the riveting characteristic curve;
And the riveting characteristic curve comprises any one or a combination of a plurality of riveting force-riveting stroke curve (F-S), riveting force-time curve (F-t) and riveting stroke-riveting force-riveting time (F-S-t). The riveting characteristic curve is controlled based on a riveting force-riveting stroke curve, is not influenced by time (loading speed and riveting speed), and is controlled and monitored through a force-time curve after entering a retention stage.
In the above-mentioned numerical control riveting system based on variable data chain, the variable cluster further includes a real-time electrical signal self-monitored by a system circuit, during the riveting operation, the numerical control riveting system monitors the riveting working condition in real time, acquires the real-time voltage/current of the driving motor, and generates a two-dimensional/three-dimensional extended riveting characteristic curve with the acquired real-time riveting force and/or riveting stroke, including any one or a combination of multiple of an I-t (motor current-riveting time) curve, a V-t (motor voltage-riveting time) curve, an F-I (riveting force-motor current) curve, an F-P (riveting force-motor output power) curve, an S-t (riveting stroke-riveting time) curve, an S-I (riveting stroke-motor current) curve, an S-P (riveting force-riveting stroke-motor current) curve, and an F-S-P (riveting force-riveting stroke-motor output power) curve.
In the numerical control riveting system based on the variable data chain, the numerical control riveting system comprises an electric control main board, a storage module and/or a transmission module connected to the electric control main board, a display module and control keys on the display module;
the riveting force is obtained through a riveting force sensor, the riveting force sensor is a pressure sensor arranged in a sensor cavity in a power mechanism frame, the riveting power mechanism comprises a main shaft used for connecting a riveting functional component, the main shaft circumferentially movably penetrates through the pressure sensor, a front thrust bearing and a rear thrust bearing are respectively arranged on two sides of the main shaft positioned on the pressure sensor, and when the main shaft bears an axial load, the axial load can be converted into pressure between the front thrust bearing and/or the rear thrust bearing and the pressure sensor through the front thrust bearing and/or the rear thrust bearing;
the riveting stroke is obtained through an angle sensor, the riveting power mechanism comprises a motor and a gearbox, the gearbox drives an output shaft of a main shaft to rotate, and the angle sensor is arranged on the output shaft.
For the possible abnormal state in the riveting process, the method also provides a monitoring protection method:
1) Determining a limit range of any one or more protection items of the service life, the maintenance period, the motor voltage, the motor current, the riveting force, the riveting stroke and the thickness of the riveting workpiece according to riveting fastener parameters input/selected by a user;
2) And monitoring whether each protection item exceeds the corresponding limit value range in real time, giving an alarm prompt to a user and/or cutting off a power supply according to a priority level when any protection item exceeds the corresponding limit value, and storing a riveting process function f (& gt) data chain, a riveting characteristic curve and/or a riveting characteristic vector.
For the possible abnormal interruption in the riveting process, the method also provides an exit travel monitoring method for the forced exit of the user:
1) Calculating whether the reverse stroke is larger than the sum of the forward fastening stroke and the corresponding stroke of the protection turns;
2) If yes, giving a prompt that the user can perform subsequent operation;
3) If not, giving an alarm prompt to the user.
For abnormal interruption in the riveting process, the method also provides a follow-up riveting monitoring method after the user forcedly exits:
1) Judging the riveting stage according to the abnormal break point;
2) If the abnormal break point is before plastic deformation of the riveting fastener occurs, re-riveting is allowed;
3) If the abnormal break point is after plastic deformation of the riveting fastener and no upsetting head is formed, allowing re-riveting and transmitting a control datum point in the process of breaking the riveting;
4) If the abnormal break point is after the riveting fastener forms an upsetting head, re-riveting is limited, and an alarm prompt is given to a user.
For abnormal operation in Shi Mao/forced withdrawal/continuous riveting process, the method also provides a fool-proof protection method:
1) Monitoring whether the motor switch is loosened according to the operation rule requirement in real time;
2) Monitoring whether the steering is switched according to the operation procedure requirement in real time;
3) If either of the above two cases occurs according to the state value, it is determined that there is an abnormal operation, and the power supply is turned off.
The method also provides a low-power monitoring protection method:
and monitoring whether the battery electric quantity is smaller than the warning limit value in real time, and entering the last riveting limit when the battery electric quantity is smaller than the warning limit value.
In the above-mentioned numerical control riveting system, the numerical control riveting system performs uploading and/or downloading of riveting process data in a standard data exchange format, and can be used for remote control and/or online diagnosis of the riveting process by being connected to a manufacturing system through a network.
The invention has the advantages that:
By stress-strain analysis of the rivet nut header formation during the riveting process, a controlled riveting force is critical to header formation and consistency. The riveting force is insufficient, the strain quantity is insufficient, the compression is insufficient, the loosening and falling of the riveting nut can be caused, the riveting force is overloaded, the riveting workpiece is required for the far-super-strong connection of the residual stress of the mounting hole of the thin plate piece, the stress concentration and even the generation of initial cracks occur, and the structural performance of the riveting workpiece is reduced. The proper riveting force is affected by parameters such as the material and thickness of the riveted fastener, and incorrect parameter setting can lead to improper riveting force, thereby affecting the forming quality of the upsetting head of the rivet nut. Meanwhile, the loading and the holding of the riveting force in the riveting process are correspondingly represented as the riveting speed in the time dimension, and the riveting speed directly affects the upsetting of the riveting nut and the residual stress of the riveting workpiece, namely the riveting speed comprising elastic deformation and plastic forming stages in the riveting process is theoretically matched with the stress-strain energy absorption speed of the riveting nut in the material mechanical property, so that the situation balance of energy conversion is realized, and the adverse effect caused by the residual stress is avoided.
According to the invention, the stress strain of the riveting fastener in the time dimension is controlled through the riveting force and the riveting speed, so that the residual stress is controlled, the fastening utility and the fastening precision are ensured, wherein the stress strain can be represented by the riveting force and the riveting stroke to form a parameter variable point set which is used as a measuring/controlling object of the system.
In addition, the numerical control riveting system provided by the invention is used for constructing a coordinate reference system by corresponding variable clusters to parameter variables of a riveting process one by one, defining a reference origin 0 of the riveting process variable clusters, monitoring riveting working conditions in real time, generating a current riveting process function f' (. Cndot.) and a riveting characteristic curve, and obtaining a riveting characteristic vector for digital automatic control and diagnosis of the riveting process. According to the self-adaptive riveting force control method based on the mechanical characteristics of materials, the mechanical characteristic points of elastic-plastic deformation conversion and the critical load thereof are used as control references, the optimal riveting stop point of upsetting forming can be self-adaptively determined, and a self-adaptive control strategy irrelevant to parameter setting is formed, so that the riveting problems of over riveting/under riveting and the like caused by difficult judgment of the optimal riveting end point due to the specification and model of a riveting fastener and/or the thickness difference of a riveting workpiece can be effectively avoided as shown in fig. 2 (c). Setting a withdrawal stage, and realizing accurate control of the riveting process through controllable riveting force in a time dimension at the stage, so as to ensure consistency of riveting quality;
The numerical control riveting system provided by the invention can monitor the riveting working process in a full time, can realize continuous monitoring of the riveting force from light load to heavy load through the embedded pressure sensor, can generate a riveting characteristic curve in real time based on the riveting force, and can acquire a control datum point and a self-adaptive riveting stop point based on the mechanical characteristics of a riveting fastener material through accurately identifying the conversion characteristic points (namely characteristic points) of all load objects in the riveting process based on the riveting process function f' (-), the riveting characteristic curve and/or the riveting characteristic vector. The control datum point and the self-adaptive riveting stop point are only related to the material mechanical characteristics of the riveting fastener, can realize fault tolerance on the influence of system errors such as sensor errors, friction force, pretension spring force and the like, can ensure that the optimal stop point is obtained in a self-adaptive manner in the riveting process, does not depend on the experience of operators, can improve the high efficiency and high precision of riveting work and can effectively ensure the consistency of riveting quality, and the thickness change of the riveting workpiece in a permissible range is not influenced;
According to the numerical control riveting system provided by the invention, according to system configuration and user selection/input, based on a riveting process function f (-) obtained by multiple tests, the riveting force-riveting time and/or the riveting force-riveting stroke and/or the motor current-riveting time and/or the motor current-riveting stroke optimal control reference riveting characteristic curve are generated by statistics calculation, the output power of a driving motor is controlled in the whole riveting process, a riveting force loading speed control power system parameter model is automatically preset according to the selected riveting fastener specification material in a grading manner, the riveting speed of each stage in the riveting process is optimally controlled, the riveting speed matched with the riveting fastener stress energy absorbing speed in the stage is provided while the output energy matched with the material mechanical characteristics in the stage is provided by a power system, so that the influence of the riveting residual stress on the riveting surface quality is minimized;
the numerical control riveting system provided by the invention can also continuously monitor the voltage/current of a motor, the riveting times, the riveting time and the like in the riveting process, realize full-time diagnosis and intelligent management of the riveting process based on a riveting process function f' (-), a riveting characteristic curve and/or a riveting characteristic point and a characteristic vector, realize the material mixing diagnosis of a riveting fastener in the riveting process and the intelligent management of abnormal detection of the riveting process, further realize the evaluation of the riveting quality through the diagnosis and the management of the process, and eliminate unqualified riveting work in advance so as to replace or greatly reduce destructive verification of high cost afterwards, effectively reduce various losses caused by the unqualified riveting work and form intelligent management and control of the riveting process.
Drawings
FIG. 1a, FIG. 1b is a schematic illustration of the material partitioning and heading of a rivet nut;
fig. 2a, 2b and 2c are schematic views of the influence on the riveting quality in three different rivet control modes, wherein fig. 2a is a manual control riveting force output mode in the same riveting workpiece thickness, fig. 2b is a riveting stroke fixed value control mode in different riveting workpiece thicknesses, and fig. 2c is a digital fastening control mode in different riveting workpiece thicknesses.
FIG. 3 is a system block diagram of a numerical control riveting system;
FIG. 4 is a schematic illustration of a riveting device with a rivet nut function assembly installed;
FIG. 5 is a graph showing the F-t (force-time) characteristic curve and the stage of the riveting process of the rivet nut;
FIG. 6 is a graph of riveting force versus riveting time versus riveting feature vectors in a coordinate system;
FIG. 7 is a process curve of F-S (force-stroke) loading and unloading for a rivet nut staking process;
FIG. 8 is a graph of riveting force versus riveting stroke versus riveting feature vector in a reference coordinate system;
FIG. 9 is a schematic diagram of the operation of the numerically controlled riveting system;
FIG. 10 is a schematic illustration of the pretension present during the riveting stroke of the rivet nut;
FIG. 11 is a schematic illustration of adaptive riveting force control in a riveting force-riveting time reference coordinate system during a riveting process of a riveting nut;
Fig. 12 is a schematic diagram of adaptive riveting force control in a riveting force-riveting stroke reference coordinate system during the riveting process of the rivet nut.
Reference numerals: a screw 1; a main function pipe 2; an inner tube 3; a main shaft 4; a pressure sensor 5; a flange 6; a frame 7; a pinion 8; a motor 9; an angle sensor 10; an angle sensor pin 11; a large gear 12; a rear thrust bearing base 13; a rear thrust bearing 14; a rotation stopping plunger 15; a guide nozzle 16; a front thrust bearing 17; a front thrust bearing block 18; a shoulder 19; a sensor cavity 20.
Detailed Description
The invention will be described in further detail with reference to the drawings and the detailed description.
The proposal provides a numerical control riveting system which can acquire and realize the control of the riveting process and/or the diagnosis of the riveting process according to the riveting force or the riveting force and the riveting stroke. By the system configuration and/or specific design, the self-adaptive numerical control riveting system only has the riveting process control capability, or only has the riveting process diagnosis capability, or has both the riveting process control capability and the riveting process diagnosis capability. As shown in fig. 3, the numerical control riveting system is used for connecting a riveting power mechanism of a riveting device, and in actual use, the numerical control riveting system can be integrated with the riveting power mechanism, can be separately arranged with the riveting power mechanism and can be detachably arranged and connected through a data line or wireless network communication. The riveting power mechanism comprises a power unit and a transmission system. Specifically, the numerical control riveting system is connected to a riveting force sensor for monitoring a riveting force during a riveting work and/or a riveting stroke sensor for monitoring a riveting stroke during the riveting work, and the riveting force sensor and the riveting process sensor are preferably connected at the same time in this embodiment.
The drive train includes a spindle for connecting a rivet function assembly for installing a rivet fastener. The numerical control riveting system is connected with a riveting force sensor which is arranged in a riveting power mechanism and used for monitoring riveting force in the riveting working process and a riveting stroke sensor which is used for monitoring riveting stroke as shown in fig. 4, wherein the riveting force sensor is a pressure sensor 5 in the embodiment, and the riveting stroke sensor is an angle sensor 10.
Specifically, as shown in fig. 4, the pressure sensor 5 is located in a sensor cavity 20 in the frame, a main shaft 4 of the riveting power mechanism is penetrated in the pressure sensor 5 in a circumferential movable manner, a front thrust bearing 17 and a rear thrust bearing 14 are respectively arranged on two sides of the main shaft 4 located on the pressure sensor 5, and when the main shaft 4 bears an axial load, the axial load can be converted into pressure between the front thrust bearing 17 and/or the rear thrust bearing 14 and the pressure sensor 5 through the front thrust bearing 17 and/or the rear thrust bearing 14. The main shaft 4 is in threaded connection with the inner tube 3 of the riveting functional component, and can drive the inner tube 3 to move back and forth relative to the frame when the main shaft 4 rotates forward or reversely. The spindle 4 penetrates through the middle of the pressure sensor 5 to realize that the pressure sensor does not interfere rotation of the spindle 4, the front thrust bearing 17 and the rear thrust bearing 14 are utilized to realize that axial load of the spindle 4 is converted into pressure to the pressure sensor 5, and the pressure value of the pressure sensor 5 is Force with the same axial load of the spindle and opposite direction, so that the axial load of the spindle can be sensed by the pressure sensor to obtain the riveting Force of the spindle 4 transmitted to a fastener by the inner tube 3, and a pressure signal is output as the riveting Force, or the pressure signal is used as the riveting Force after axial sliding friction Force compensation is carried out on the pressure signal based on the axial sliding friction coefficient of a riveting power mechanism transmission system.
One end of the main shaft 4 is an input end connected with the power mechanism, the other end is an output end in threaded connection with the inner tube 3, a shaft shoulder is arranged on the input end, a rear thrust bearing seat 13 is fixedly connected in the frame, and a rear thrust bearing 14 is nested between the rear thrust bearing seat 13 and the shaft shoulder 19. The rear thrust bearing 14 and the shaft shoulder 19 function to ensure that the normal circumferential rotation of the main shaft 4 is not affected and simultaneously can transmit axial load, the stress of the axial load is positioned in the rear thrust bearing seat 13, and the rear thrust bearing seat 13 is fixedly connected with the frame 7 through the flange 14 which is coaxially and fixedly connected, so that the axial load on one side of the main shaft 4 close to the rear thrust bearing 14 directly acts on the frame 7, and the freedom degree of the main shaft in the axial direction is limited and only circumferential rotation is realized. A main functional pipe 2 is arranged between the frame 7 and the inner pipe 3, a front thrust bearing seat 18 is arranged at one end of the main functional pipe 2 far away from the inner pipe 3, and the front thrust bearing 17 is arranged in the front thrust bearing seat 18. The main function pipe 2 is provided with the front thrust bearing seat 18, so that when the main function pipe 2 acts on the riveting function component through the main function pipe 4, the axial force generated by the main shaft 4 directly acts on the front thrust bearing 17 through the main function pipe 2, the front thrust bearing 17 is in contact with one side of the pressure sensor 5, the other side of the pressure sensor 5 is abutted against the side wall of the sensor cavity 20, the side wall of the sensor cavity 20 is used as a bearing surface, and the transmission of the axial load (namely the riveting tension) of the main shaft from the riveting function component, namely the main function pipe 2, the front thrust bearing 17 and the pressure sensor 5 is realized, and the pressure sensed by the pressure sensor 5 is the real-time reaction of the riveting tension. One end of the pressure sensor 5 can be attached to the front thrust bearing 17, and the other end of the pressure sensor is abutted against one side of the sensor cavity 20 away from the front thrust bearing 17. One end of the pressure sensor 5 is abutted against the side wall of the sensor cavity 20, so that the other side is ensured to be in pressure contact with the front thrust bearing in the initial installation state 0 to ensure the reference position design of the pressure sensor 0. A clearance gap is left between the front thrust bearing 17 and the pressure sensor 5. The clearance gap may also ensure a 0-reference design of the pressure sensor 5.
The main functional pipe 2 is rotationally connected with the frame 7, and the frame 7 is also provided with a rotation stopping structure which can control the main functional pipe 2 to rotate and lock relative to the frame 7. In order to adapt to the expandability of different functions, the main function pipe 2 needs to have the freedom degree of circumferential rotation in the frame, and the different functions of the riveting device can be switched through locking and unlocking the freedom degree of the main function pipe 2 by the rotation stopping structure. When the main functional pipe 2 can rotate, the riveting device can screw in the riveting nut and unscrew the riveting nut which is already riveted through the screw rod 1; when the main function pipe 2 is locked, the riveting device enters a pull rivet state.
The main functional pipe 2 is rotationally connected with the frame 7, and the frame 7 is also provided with a rotation stopping structure which can control the main functional pipe 2 to rotate and lock relative to the frame 7. In order to adapt to different working occasions, the main functional pipe 2 needs to have the freedom degree of circumferential rotation in the frame 7, and different functions of the riveting device can be switched through locking and unlocking the freedom degree of the main functional pipe 2 by the rotation stopping mechanism. If the expansibility of the riveting function is not considered, only the riveting function of the rivet nut is considered, the design of the locking structure can be simplified by a person skilled in the art, and the details are not repeated here. The specific structure of the rotation stopping structure is not limited, and a person skilled in the art can set the rotation stopping structure by himself according to selection, for example, the rotation stopping structure comprises a rotation stopping plunger 15 penetrating through a frame, a rotation stopping hole is arranged on the main function pipe 2, the rotation stopping plunger 15 can penetrate into the rotation stopping hole, and when the rotation stopping plunger 15 penetrates into the rotation stopping hole, the rotation freedom degree of the main function pipe 2 which can rotate in the circumferential direction is locked and cannot rotate; after the rotation stop plunger 15 leaves the rotation stop hole, the main function pipe 2 resumes the degree of freedom rotatable in the axial direction.
The power unit comprises a motor 18 and a gearbox, the gearbox comprises an output shaft for driving the main shaft to rotate, the output shaft is provided with an angle sensor 10, the rotation motion of the output shaft can be converted into the axial motion of the riveting functional component, and the axial motion displacement can be used for identifying the axial motion as a riveting process parameter riveting Stroke. Through the calculation of the angle of the output shaft, the rotating angle of the main shaft can be obtained, the linear displacement can be converted through the thread size, and then the stroke parameter of the rivet pulling can be calculated.
The gearbox comprises an input shaft pinion 8 connected with the motor and an output shaft big gear 12 connected with the output shaft, and a speed reducing gear set is arranged between the input shaft pinion 8 and the output shaft big gear 12. Through the speed reduction gear group and the small teeth and the big teeth in the gearbox, the torque transmitted to the main shaft 4 by the motor 9 can be amplified, and meanwhile, the rotating speed output to the main shaft 4 by the motor 9 can be reduced to be suitable for the turning and reading of riveting work, so that the method is a foundation for realizing heavy-load riveting.
In this embodiment, the monitoring of the riveting force and the riveting stroke is achieved through the foregoing structure, and if a person skilled in the art can achieve the obtaining of the riveting force and the riveting stroke through other structures, the numerical control riveting system based on the variable data chain and achieved through the riveting stroke and the riveting force obtained through the new structure based on the new method is also within the protection scope of the present application.
Further, the numerical control riveting system based on the variable data chain comprises an electric control main board, a display module, a storage module, a transmission module and the like which are connected to the electric control main board, wherein the display module can be a touch display screen or is composed of a display module and operation control keys.
The numerical control riveting system is used for setting the coordinate origin of the riveting process parameter variables based on the riveting fastener riveting process in the riveting process, constructing a coordinate reference system among the riveting process parameter variables, marking the riveting process parameter variables obtained in the riveting process in the coordinate reference system to obtain variable data chains composed of the riveting process parameter variables, and then performing riveting control and/or riveting diagnosis by the numerical control riveting system according to the characteristics of the variable data chains.
The riveting process parameter variables comprise riveting force, and the coordinate reference system comprises a riveting force-time coordinate system; or, the parameter variables comprise riveting force and riveting stroke, and the coordinate reference system comprises any one or more of a riveting force-time coordinate system, a riveting force-riveting stroke coordinate system, a riveting stroke-time coordinate system or a riveting force-riveting time-riveting stroke coordinate system;
And correspondingly, the variable data chain comprises any one or more of a variable point set of riveting force changing along with time, a variable point set of riveting force changing along with riveting stroke, a variable point set of riveting stroke changing along with time, or a variable point set of riveting force and riveting stroke along with time.
In this embodiment, the control and diagnosis are mainly performed around the riveting force-riveting stroke-time, and the variable data chain takes two types of riveting force-riveting stroke and riveting force-time, and specific usage will be described later.
The origin of coordinates 0 of the riveting process parameter variables as the coordinate reference system variable clusters are set as follows:
setting an origin 0 of a riveting process parameter variable riveting Force by taking an origin of an effective Shi Mao load as a reference origin, wherein the measured value of a riveting Force sensor increases linearly in the same direction along with the increase of a riveting load from 0, and the reading of the riveting Force sensor returns to 0 when the Shi Mao load is completely unloaded, wherein the minimum measured value of the riveting Force sensor is 0;
setting an origin 0 of a riveting process parameter variable riveting Stroke by taking an origin of an effective Shi Mao load as a reference origin, wherein the measured value of a riveting Stroke sensor linearly changes in the same direction along with the axial displacement (rotation angle) of a transmission system, and the riveting Stroke can be a negative value and is used for representing a reverse withdrawal Stroke;
Setting an origin 0 of riveting process parameter variable riveting time t by taking the origin of an effective Shi Mao load as a reference origin, wherein the time t is a natural variable;
the rivet force is equal to the pretension threshold and is considered the starting point for the effective Shi Mao load.
Specifically, the numerical control riveting system tracks and analyzes parameter variables of a riveting process of the space vector, acquires at least one characteristic point and a characteristic vector formed by a characteristic point set, and performs riveting control and/or riveting diagnosis according to the characteristic point and the characteristic vector;
the characteristic points comprise any one or more of an elastic-plastic conversion point Datum, a riveting starting point Fs, a second entity point Pier, a riveting force peak point Fmax, a rebound unloading point Fr and a Shi Mao end point Fe;
the numerical control riveting system divides the standard riveting process into three or four typical stages by identifying each characteristic point of the riveting process, a Forming stage, a Yielding stage, a Setting stage and a fourth typical stage restination stage, wherein:
the Forming stage corresponds to a section from the riveting starting point Fs to the elastic-plastic conversion point Datum, and is an elastic deformation stage of the riveting fastener under the action of load;
the YIelding stage corresponds to a section from an elastic-plastic conversion point Datum to a second entity point Pier, and is a plastic deformation upsetting stage of the riveting fastener under the effect of riveting load and constrained by the wall of a hole of a riveting workpiece;
The Setting stage corresponds to a section from the Pier to a riveting force peak value Fmax of a second entity point, and is a plastic deformation upsetting-second entity upsetting Preform forming stage of the riveting fastener under the effect of riveting load and constrained by the wall of a riveting workpiece hole and the contact surface of the upsetting;
the restination stage corresponds to the interval from the riveting force peak point Fmax to the rebound unloading point Fr, and is an optimized forming stage for maintaining the Shi Mao load of the riveting fastener to eliminate the influence of residual stress.
Preferably, the numerical control riveting system generates and outputs a riveting characteristic curve smoothly passing through the riveting process parameter variables according to the set coordinate origin based on the coordinate reference system, the riveting characteristic curve describes the association relation between the riveting process parameter variables in the coordinate reference system, the numerical control riveting system identifies each characteristic point and the riveting characteristic vector by analyzing the riveting characteristic curve, performs riveting control and/or riveting diagnosis based on the riveting characteristic curve, and divides the standard riveting process into four typical stages based on the riveting characteristic curve.
That is, it is preferable to use the caulking characteristic curve for caulking control and caulking diagnosis, but it is also within the scope of the present application to obtain the caulking characteristic point by directly using the coordinate reference system and dropping the caulking process parameter variable in the coordinate reference system without using the caulking characteristic curve, and further control and diagnosis of the caulking process.
The riveting characteristic curve includes any one or a combination of a plurality of riveting force-riveting stroke curve (F-S) shown in fig. 12, riveting force-time curve (F-t) shown in fig. 5 and 10, and riveting force-riveting time (F-S-t) corresponding to the variable data chain. When the device is put into use, a riveting force-riveting stroke curve (F-S) and a riveting force-time curve (F-t) are simultaneously generated, or a three-dimensional curve of the riveting stroke-the riveting force-the riveting time (F-S-t) is generated.
Since the riveting force-riveting stroke curve is not affected by time, loading speed, and riveting speed, the control is mainly based on the riveting force-riveting stroke in the control process. Furthermore, since the present system sets a retention phase after which the force-travel curve is invisible, this phase is controlled and monitored by the force-time curve.
When the numerical control riveting system is put into use, a riveting characteristic curve, such as an F-t (riveting force-riveting time) curve shown in fig. 5, is generated according to the real-time riveting force acquired by the riveting force sensor and the real-time riveting stroke acquired by the riveting stroke sensor in the riveting work process. In the load Shi Mao riveting stroke, the riveting fastener is subjected to riveting load action, enters an elastic deformation Forming stage of the riveting fastener under the load action, when the elastic deformation Forming stage is higher than yield strength, the riveting fastener is subjected to the load action and is restrained by the installation hole wall of the riveting workpiece, plastic deformation upsetting is generated, the plastic deformation upsetting stage is a YIelding stage, under the further load action, the riveting workpiece hole wall and the contact surface are restrained to form a upsetting head, the fastening of the riveting workpiece is finally completed, the riveting stage is called a Setting stage, the residual stress is eliminated, the load of the riveting fastener can be selectively kept for a period of time, and the Forming of the riveting fastener is optimized, and the riveting stage is called a restination stage.
As shown in FIG. 5, the riveting characteristic curve (F-t curve) has a clearly separable load characteristic transition point corresponding to the Forming, yielding, setting, retention stage transition process, including a riveting start point F s Elastic-plastic transformation point Datum, second solid point Pier, and riveting force peak point F max 、F r Rebound unloading point, F e Shi Mao end point, etc., thereby constituting a caulking feature vector as shown in fig. 6. The riveting characteristic curve (F-S curve) shown in FIG. 7, the clearly separable load characteristic transition points corresponding to the Forming, yielding, setting stage transition process, includeRiveting start point F s Elastic-plastic transformation point Datum, second solid point Pier, and riveting force peak point F max 、F e Shi Mao end points, etc., to constitute a caulking feature vector as shown in fig. 8.
The riveting fastener is a load object under the action of controllable riveting force, and the purpose of the riveting load is to enable the riveting nut of the riveting fastener to generate plastic deformation in a stretching area or a thin-wall deformation area shown in figure 1, upsetting and further forming a upsetting head so as to fasten a riveting workpiece, and provide conditions for riveting action on a riveting stroke.
The formation of the upsetting marks that the expansion area or thin-wall deformation area of the rivet nut starts to be restrained by the surface of the riveted workpiece, the material of the expansion area or thin-wall deformation area is expressed as an outer drum and flows in the circumferential direction to form an outward protruding entity, the entity forms a new entity which plays a role in fastening the riveted workpiece in the mechanical sense, the entity can also be called as a second entity, the entity is expressed as a conversion from YIelding to Setting stage in the riveting process in the mechanical feature, and a load object feature inflection point appears on a riveting feature curve, namely a Pier second entity point shown in fig. 5 and 7. It is also noted that the pin second solid point can be identified as the feature transition point of the load object for the caulking force-caulking time as shown in fig. 6 or the caulking feature vector in the caulking force-caulking stroke coordinate system as shown in fig. 8. The Setting phase, which starts with the second solid point of pin, is a critical phase for upset shaping, and requires the system to provide a suitable controlled rivet force in order for the second solid to develop a sufficiently suitable strain under stress.
The expanded region (DuctileArea) of the clinch nut, as shown in FIG. 1, is the region where the clinch nut is plastically deformed under the force of the clinching to form a upset head, and is structurally thin-walled with respect to the head and threaded region, and is therefore also referred to as a thin-walled deformed region. In the YIelding stage, the material in the extensible area is plastically deformed to flow in axial direction and to form a upsetting and outer drum, which is in contact with the wall of the installation hole of the riveted workpiece to form an anti-torsion structure, and after being restrained by the wall of the installation hole to the material flow, the extensible area of the upsetting outer drum begins to form circumferential material flow along the outer drum of the surface of the riveted workpiece to connect with the surface of the riveted workpieceAnd (3) forming an upsetting head by touching, and finally realizing the fastening function on the riveted workpiece in the Setting stage. And when the second entity, namely the upsetting head is formed, the second entity is influenced by the contact pressure of the surface of the riveted workpiece and the mounting hole wall, the corresponding riveting force can generate a load object characteristic inflection point, and a rapid rising trend is shown, namely Pier second entity points. Since the thickness e of the rivet work affects the outer drum of the expansion area of the rivet nut and the position (L) d -e, wherein L d Height of the extension area) and the amount of the material, so that the riveting stroke and the riveting force corresponding to the Pier second entity point have an association relation with the thickness of the riveted workpiece for the riveting characteristic vector in the riveting force-riveting stroke coordinate system shown in fig. 8, and can be used for measuring and calculating the thickness interval of the riveted workpiece. Whereas considering the expansion zone, the material flow of the upset head formation needs to be considered, so that there is a suitable rivet work thickness threshold (e <L d ). Therefore, the acquired thickness interval of the riveting workpiece can be used for diagnosing whether the thickness interval exceeds an important basis of the thickness threshold value of the riveting workpiece or not, and can also be used as a calculation basis of self-adaptive riveting force compensation.
As shown in fig. 5 and 7, the Forming stage is represented as a continuous rise in the caulking force under the caulking load, corresponding to the elastic loading curve of the first stage on the caulking characteristic curve. When the elastic loading peak value (first riveting force peak value) is reached, the riveting fastener starts to plastically collapse and deform, the load in the riveting process becomes smaller, a characteristic conversion inflection point of a load object appears, and the conversion from a Forming stage to a YIelding stage is marked and is called a Datum elastic-plastic conversion point. Datum is a characteristic point directly related to the individual riveting fastener, and the characteristic values can represent the mechanical characteristics of materials such as elastic modulus and the like, and are related to the material, specification and structure of the riveting fastener, so that the characteristic point can be used as a Datum point for riveting force control.
In the Setting riveting and fastening stage, the riveting force is a key factor of upsetting shaping, in a manual mode, the control of the riveting action depends on experience of an operator, namely the operator is required to determine an optimal time point for ending the riveting action, under-riveting is easily caused by insufficient riveting force when the operator is required to finish the riveting action too early, and over-riveting problem is caused by overload of the riveting force when the operator is too late. Since the riveting force at the Setting stage appears to rise rapidly, a slight difference in the end time also causes a significant difference in the riveting force, resulting in the occurrence of a riveting problem, and even an experienced operator has difficulty in ensuring consistency in the riveting quality. According to the scheme, the riveting force, the riveting time, the riveting stroke and the parameter variables are used, the characteristic conversion points of all load objects are accurately identified by the riveting characteristic curve based on the parameter variable point set, then the optimal stop point is determined according to the object characteristic conversion points to finish the loading action, the experience of operators is not relied on, the high efficiency and the high precision of the riveting work are improved, and meanwhile the consistency of the riveting quality can be effectively ensured.
And (3) riveting process control:
the riveting control of the numerical control riveting system according to the characteristics of the variable data chain comprises riveting control in any one or more combination modes of a Dummy test mode, a Parametric Riveting parameter mode, a Adaptive Riveting self-adaptive mode and a Resume riveting mode.
The user selects the corresponding mode when using and then enters the riveting control or the riveting diagnosis of the corresponding mode.
Parametric Riveting control procedure in parametric mode:
SA1, selecting a parametric Riveting mode by a user, selecting a Riveting nut specification material to be used according to a system prompt, and presetting a stop point Riveting force peak value Fmax according to the input Riveting nut specification material by the system;
SA2, uploading a riveting fastener, starting a power unit of a riveting power mechanism to pretighten the riveting fastener, and monitoring whether the axial force is higher than a pretightening force threshold value in real time by a numerical control riveting system, and setting a coordinate origin to construct a coordinate reference system when the axial force is higher than the pretightening force threshold value, wherein the machine can be stopped firstly or not;
SA3, continuously applying load to enter a riveting stroke by the numerical control riveting system, monitoring the riveting force or the riveting force and the riveting stroke in real time, and generating a value monitored in real time as a variable cluster of a coordinate reference system to the coordinate reference system; the embodiment also generates corresponding curves, such as a riveting force-time curve and a riveting force-stroke curve.
SA4, monitoring parameter variables of a riveting process in a coordinate reference system, obtaining an elastic-plastic conversion point Datum, specifically obtaining Datum by analyzing a riveting force-stroke curve, comparing the Datum with a pre-stored Datum range corresponding to a riveting nut specification material as a riveting process diagnosis reference point, giving a prompt if the Datum exceeds the range, and automatically switching to a self-adaptive mode to continue riveting control so as to avoid riveting problems such as under riveting, over riveting and the like or riveting accidents such as sliding of a riveting nut, breakage of a pull rod and the like caused by error of the riveting nut specification material selected by a user in SP 1; otherwise, continuing to execute SA5;
SA5 monitoring whether the riveting force in the coordinate reference system reaches the peak value F of the riveting force at the stop point max If yes, automatically cutting off the power supply to finish the riveting action according to the preset, or automatically cutting off the power supply to finish the riveting action after the riveting force is kept for a period of time according to the riveting force-time curve. When the offset is preset, an adjustable range of the riveting force threshold is determined according to the preset experience offset, and the riveting action is automatically ended at any point in the adjustable range according to the action of the user.
The system pre-stores riveting process functions f (x) corresponding to the riveting nuts of various specifications, the riveting process functions f (x) comprise variable data chains, namely riveting force, riveting stroke and riveting time variable point sets, and in step SA1, corresponding f (-) is obtained based on riveting nut specification materials, so that a riveting force peak value Fmax is determined. The duration of the period of time in SA5 may be a set duration, or the duration may be determined according to the riveting process function f (·).
Control process of the rising adaptive mode:
SB1, selecting a Riveting self-adaptive mode by a user, selecting/inputting a rivet nut specification material to be used, firstly uploading a Riveting fastener in working, sleeving the rivet nut into a screw 1, unlocking a main functional pipe, switching on a power supply to start a power unit of a Riveting power mechanism to pretighten the Riveting fastener, adopting a sliding window to read a pressure average value or taking the maximum pretightening force as a pressure value by a numerical control Riveting system, monitoring whether the pressure is higher than a pretightening force threshold in real time, taking the action of the pretightening spring (shown in fig. 10) into consideration, taking an experience value constant 50N as the pretightening force threshold, ensuring that the contact pressure of the fastening piece and the front end face of a machine guide nozzle is greater than the threshold when entering a formal Riveting process, leading the contact pressure between the two planes to play a role in guiding, preventing the Riveting nut from deviating, then inserting the fastening piece into a workpiece plate hole and compacting, ensuring that the fastening piece is vertical to the plate plane, and preventing Riveting or deviating, setting a coordinate reference system when the numerical control system monitors that the pressure reaches the pretightening force threshold, and automatically stopping when the pretightening force threshold is reached; after the numerical control riveting system starts a riveting process parameter variable monitoring coordinate system, restarting riveting after aligning the riveting fastener with the riveting workpiece;
SB2, locking the main functional pipe, switching on a power supply, applying load by a numerical control riveting system to enter a riveting stroke, monitoring the riveting force and the riveting stroke in real time, generating a value monitored in real time as a variable cluster of a coordinate reference system to the coordinate reference system, and simultaneously generating a riveting characteristic curve in the embodiment;
SB3, when the elastic-plastic deformation inflection point (shown in fig. 11 or 12) appears on the riveting fastener, the numerical control riveting system recognizes a first riveting force peak value Datum as a control reference point according to the riveting characteristic curve, and calculates a riveting force peak value Fmax and the upper limit and the lower limit of the self-adaptive stopping point according to the control reference point Datum;
SB4, continuing to monitor a second entity Point Pier (as shown in FIG. 11 or FIG. 12) through the riveting characteristic curve, after the second entity Point Pier appears, indicating to enter a Setting stage, and when the real-time riveting force reaches a riveting force peak value Fmax, acquiring an adaptive stopping Point X-Point (as shown in FIG. 11 or FIG. 12), and executing step SB5;
SB5, the numerical control riveting system selects to automatically cut off the power supply to finish the riveting action according to the preset, or selects to enter a reporting stage, monitors time and riveting force, controls the riveting force to gradually drop to zero along the gradient in the set time to cut off the power supply of the motor to finish the riveting action, or keeps the riveting force in the reporting stage to cut off the power supply of the motor to finish the riveting action after the riveting force threshold value reaches the set time;
When the offset is preset, an adjustable range of the riveting force threshold is determined based on the riveting force peak Fmax according to the preset experience offset, step SB5 is executed based on the riveting force adjustable range, or the riveting action is ended automatically or according to the action of the user at any point in the adjustable range.
The system also pre-stores the optimal specific function relation corresponding to Datum and corresponding to the riveting force peak value Fmax, and various riveting nuts are subjected to riveting test in advance by a technician to determine. In step SB3, datum and the riveting force peak F are determined based on the elastic-plastic transition point Datum max And calculates the riveting force peak value Fmax according to the functional relation and Datum. The Datum elastic-plastic conversion point corresponds to the riveting force peak value in the Forming stage, and is expressed as an inflection point of the conversion of a load object from elastic deformation to plastic Forming on a riveting characteristic curve and is a mechanical characteristic point related to the material and specification of the riveting fastener, so that the optimal riveting force peak value F can be determined according to Datum and the result of a prior test max 。
Dummy test mode:
the Dummy test mode is used for blank drawing tests under the working condition that the uploading riveting fastener is not loaded with a riveting workpiece, a specific function relation between the corresponding riveting nut and the optimal riveting force peak value of the corresponding riveting nut can be obtained through a plurality of blank drawing tests, and a riveting process function f (-) of the corresponding riveting nut can be obtained as a reference;
Resume rivet mode:
the Resume continuous riveting mode is a strong backing continuous riveting mode under the abnormal interruption working condition in the riveting process, the numerical control riveting system acquires riveting characteristic points in the riveting working process, determines the riveting stage and the forward fastening stroke where the abnormal interruption is located, and provides strong backing protection and continuous riveting control according to the abnormal interruption working condition;
the strong backing protection is that when an abnormal interruption user forcedly exits, the numerical control riveting system stores interruption field data, monitors and confirms that the voltage/current of a motor in an exiting stroke is within a permissible range in real time, ensures that a reverse stroke is larger than the sum of corresponding strokes of a forward fastening stroke and a protection circle number, ensures that gap separation exists between a riveting nut and a guide nozzle, and enables a pull rod to continue to exit and be in threaded connection with the riveting nut;
the continuous riveting control is a mortise applying operation which is performed again after the forced withdrawal of the abnormal interruption occurs, and the numerical control riveting system controls the continuous riveting operation according to the interruption position, wherein the continuous riveting operation comprises a continuous riveting operation of the abnormal interruption in a Forming stage, a continuous riveting operation of the abnormal interruption in a YIelding stage and a continuous riveting operation of the abnormal interruption in a Setting stage.
In the riveting process, for the abnormal interruption, after the forced withdrawal of the abnormal source is eliminated, the numerical control riveting system provided by the scheme provides continuous riveting of incomplete riveting work for the repeated pull riveting in a Resume mode, namely, field protection record is carried out on interruption data, loading is carried out during continuous riveting of the Resume, and when the riveting characteristic vector is considered to be only related to a riveting fastener and a riveting workpiece, the riveting force peak value F can still be obtained according to the Datum acquired control Datum point while the riveting characteristic vector is unchanged max Thereby completing perfect riveting control.
In addition, the scheme can further comprise a Maintenance mode of Maintenance, wherein the Maintenance mode of Maintenance is a Maintenance mode under the working condition that riveting fasteners and riveting workpieces are not loaded, the numerical control riveting system provides a riveting speed control section according to a pre-stored riveting process function f (·) and the efficiency of the lubrication system is optimized.
Riveting process diagnostics
The riveting Force parameter, the riveting Stroke parameter, the riveting fastener parameter Rivet, the riveting times corresponding to the riveting fastener specification by the riveting workpiece parameter Workpieces can be the parameter variables of the riveting process function f (·), but are only the riveting Force, the riveting time, the riveting Stroke or other needed parameter variables in the coordinate reference system, but are not all the parameter variables of the riveting process function f (·). The riveting Force parameter pushing Force and the riveting Stroke parameter Stroke are riveting Force and riveting Stroke measured in real time in the riveting process; the Rivet fastener parameter Rivet and the Rivet workpiece parameter Workpieces are entered/selected by the user or are automatically generated in part by the user input/selection based on the entered/selected parameters. The riveting fastener parameter Rivet comprises any one or more or all of fastener specification, model, material, size and structure, and the riveting workpiece parameter Workpieces comprises any one or more or all of thickness, material and aperture of each riveting workpiece.
Before starting the riveting operation, the user selects the riveting fastener parameter Rivet, the riveting workpiece parameter Workpieces, from which the numerical control riveting system determines a pre-stored corresponding riveting process function f (-), which may be referred to as a riveting process reference function f (-) for distinguishing from the riveting process function f' (-), which also includes the riveting Force parameter Pulling Force, the riveting Stroke parameter Stroke, the riveting fastener parameter Rivet and/or the riveting workpiece parameter Workpieces. Generating a current riveting process function f' (. Degree) according to riveting fastener parameters and/or riveting workpiece parameters selected/input by a user, and riveting force and riveting stroke acquired by a riveting force sensor and a riveting stroke sensor in the riveting process, wherein if the riveting process is correct, the two functions are converged, namely, the variable parameters of the two functions have similar change rules; if the consistency is lower than the preset value, the problem that the riveting process is not qualified or the problem of the mixture of the fastener materials/the specification mixture exists is judged, the consistency is not high, whether the mixture is unqualified or the mixture is determined by the person skilled in the art according to experience is not limited. Meanwhile, considering that the control Datum point Datum is the representation of the yield strength of the riveting fastener, the yield trend should appear at the same point for the riveting fastener with the same specification, and the control Datum point Datum can also be used as an important index of the material mixing/specification mixing of the fastener for the purpose, namely in the same batch of riveting work process, if the control Datum point Datum has obvious difference in the riveting process, the problem of the material mixing/specification mixing of the fastener can be considered to exist in the riveting process.
The diagnosis process can also superimpose the background riveting characteristic curves obtained according to the riveting process reference function f (·) to compare the curve coincidence degree or the consistency of the characteristic points; the method can also be used for diagnosing the riveting process by using any one or more of off-center, centralized, off-state and peak state characteristic values in a statistical sense, including mean value, variance, off-state coefficient, kurtosis and quartile based on a statistical analysis method, including detecting whether the riveting process has abnormal process and/or judging whether the riveting quality meets the requirement by using methods such as process statistics 6 sigma, boxplot (box diagram), SPC (statistical process control) and the like. In this way, unqualified products can be removed through the observation and control of riveting process parameters, so that the problem of riveting quality caused by systematic errors or human errors can be avoided, the subsequent destructive engineering detection verification is changed into the measurement and control and threshold control of the riveting process parameters, the riveting process curve and the riveting load, and the precision, the controllability and the working efficiency of the riveting result can be greatly improved.
Specifically, in the scheme, the riveting diagnosis performed by the numerical control riveting system according to the characteristics of the variable data chain comprises any one or more of a Process diagnosis mode, a Quality diagnosis mode, a Rivet diagnosis mode and a Workpiece diagnosis mode. The system performs one or more of the diagnostic tasks based on the user selection.
Process diagnostic mode:
generating a current riveting process function f '(. Cndot.) in the riveting process, and judging whether the riveting process is remarkably abnormal or not based on a pre-stored riveting process function f' (. Cndot.) and a preset allowable deviation amount Bias thereof according to the consistency of the characteristic vector and/or the change rule of the pre-stored riveting process function f (. Cndot.) in the riveting process;
or generating and outputting a riveting characteristic curve which is smoothly subjected to riveting process parameter variables according to the set coordinate origin, standardizing the riveting characteristic curve, comparing and analyzing the riveting characteristic curve with a riveting reference characteristic curve, and using the riveting characteristic vector distance as a similarity representation for judging whether obvious abnormality exists in the riveting process;
or acquiring a riveting characteristic vector, and diagnosing the riveting process by using any one or combination of a plurality of concentrated, off-center, off-state and peak characteristic values based on a statistical analysis method of historical data, wherein the method comprises abnormality detection based on process statistics 6 sigma and/or Box Plot (Box graph) and is used for judging whether obvious abnormality exists in the riveting process;
the pre-stored riveting process function f (·) and the riveting reference characteristic curve are obtained by performing a Dummy test mode on riveting nuts shipped in batches, or by performing a Dummy test mode on one or more riveting nuts in the same batch.
A Quality diagnosis mode, wherein a current riveting process function f' (. Cndot.) is obtained in the riveting work process, a pre-stored corresponding riveting process function f (-) is obtained based on the characteristic points, and whether the riveting Quality problem caused by under riveting/over riveting exists is judged according to the comparison of the two riveting process functions;
the Quality diagnostic mode is also used for judging whether abnormal riveting Process affecting the riveting Quality exists or not based on the Process diagnostic mode, namely, through the diagnosis of the riveting working Process.
The diagnostic procedure for the Rivet diagnostic mode is as follows: acquiring a riveting characteristic vector in the riveting process, and judging whether a deviation exists between the riveting characteristic vector and a riveting fastener selected/input by a user or whether the riveting fastener has a significant difference in the riveting process in the same batch based on the material and the specification of the riveting fastener represented by the individual elastic-plastic conversion point of the Datum riveting nut, so as to be used for material mixing diagnosis;
the diagnostic procedure for the Workpiece diagnostic mode is as follows: and acquiring a riveting characteristic vector in the riveting process, and judging whether the thickness of the riveting workpiece exceeds a permissible threshold range or not or whether the thickness of the riveting workpiece has obvious difference in the same batch of riveting work based on the thickness of the riveting workpiece represented by the Datum elastic-plastic conversion point and the Pier second entity point. And measuring and calculating the thickness of the current riveting workpiece based on the travel difference between the Datum elastic-plastic conversion point and the Pier second entity point, and judging whether the thickness of the riveting workpiece exceeds a thickness threshold value of the riveting workpiece or whether the thickness of the riveting workpiece has obvious change in the riveting process or is abnormal.
As shown in fig. 9, the riveting process function f (·) may further include a Power parameter Power and a time parameter t, where the Power parameter includes parameter values such as a motor torque, a rotational speed, a motor voltage limit, a motor current limit, a motor steering switch state, etc., and the corresponding limit values may be determined according to the riveting fastener parameter Rivet and/or the riveting workpiece parameter Workpieces, such as a riveting force limit, a riveting stroke limit, a voltage limit, a current limit, etc., so as to dynamically determine and protect during the riveting process. When any item is monitored to exceed the corresponding limit value, the power supply is cut off, interruption data protection is carried out, relevant records are marked, and the abnormal riveting process is identified through limit value control in the riveting process, so that the accuracy, controllability and working efficiency of a riveting result are improved. The threshold type dynamic electric control overload protection mechanism for the parameter variable related to the riveting process is arranged between the dynamic parameter and the limit value of the riveting process, so that the system has the capability of safely coping with abnormal loads in the mechanical process of the riveting material.
Further, for the abnormal state possibly occurring in the riveting process, the method also provides a monitoring protection method:
1) Determining a limit range of any one or more protection items of the service life, the maintenance period, the motor voltage, the motor current, the riveting force, the riveting stroke and the thickness of the riveting workpiece according to riveting fastener parameters input/selected by a user;
2) And monitoring whether each protection item exceeds the corresponding limit value range in real time, giving an alarm prompt to a user and/or cutting off a power supply according to a priority level when any protection item exceeds the corresponding limit value, and storing a riveting process function f (& gt) data chain, a riveting characteristic curve and/or a riveting characteristic vector.
For the possible abnormal interruption in the riveting process, the method also provides an exit travel monitoring method for the forced exit of the user:
1) Calculating whether the reverse stroke is larger than the sum of the forward fastening stroke and the corresponding stroke of the protection turns;
2) If yes, giving a prompt that the user can perform subsequent operation;
3) If not, giving an alarm prompt to the user.
For abnormal interruption in the riveting process, the method also provides a follow-up riveting monitoring method after the user forcedly exits:
1) Judging the riveting stage according to the abnormal break point;
2) If the abnormal break point is before plastic deformation of the riveting fastener occurs, re-riveting is allowed;
3) If the abnormal break point is after plastic deformation of the riveting fastener and no upsetting head is formed, allowing re-riveting and transmitting a control datum point in the process of breaking the riveting;
4) If the abnormal break point is after the riveting fastener forms an upsetting head, re-riveting is limited, and an alarm prompt is given to a user.
For abnormal operation in Shi Mao/forced withdrawal/continuous riveting process, the method also provides a fool-proof protection method:
1) Monitoring whether the motor switch is loosened according to the operation rule requirement in real time;
2) Monitoring whether the steering is switched according to the operation procedure requirement in real time;
3) If either of the above two cases occurs according to the state value, it is determined that there is an abnormal operation, and the power supply is turned off.
The method also provides a low-power monitoring protection method:
and monitoring whether the battery electric quantity is smaller than the warning limit value in real time, and entering the last riveting limit when the battery electric quantity is smaller than the warning limit value.
As shown in fig. 8, the numerical control riveting system provides core riveting process control for a host, process parameter collection, including sampling of real-time process parameters such as pressure, travel, motor voltage, motor current, motor switch, motor steering, battery power, and the like, and provides safety protection management including overload, overcurrent, travel, overrun, low power, and the like, process parameter collection and safety protection management, and provides a callable standard module for riveting process control. Based on riveting process control parameters, the numerical control riveting system can also be used for maintenance management of a host machine, including management of service life of the whole machine, service life of vulnerable parts and the like, so that maintenance operations such as lubrication, vulnerable part replacement and the like can be timely performed.
According to the scheme, based on the mechanical characteristics of materials, the mechanical characteristic points from elastic deformation to the yield stage are used as control datum points, so that the riveting end points are adaptively controlled, an adaptive control strategy irrelevant to material setting is formed, and the riveting controllability, the riveting precision and the riveting quality are effectively improved. Further, the self-adaptive numerical control riveting system provided by the scheme can be connected into the sub-functional systems such as the hole alignment positioning system and the automatic feeding system so as to be used for an automatic riveting system. The self-adaptive numerical control riveting system can be accessed into an internet of things (IoT) for online riveting process diagnosis, and is interacted with and remotely controlled by other manufacturing system data, so that the sharing of data and the networking of control are realized.
The specific embodiments described herein are offered by way of example only to illustrate the spirit of the invention. Those skilled in the art may make various modifications or additions to the described embodiments or substitutions thereof without departing from the spirit of the invention or exceeding the scope of the invention as defined in the accompanying claims.
Claims (12)
1. The numerical control riveting system is used for setting the coordinate origin of riveting process parameter variables based on riveting fastener applying process in the riveting process, constructing a coordinate reference system among the riveting process parameter variables, marking the riveting process parameter variables obtained in the riveting process in the coordinate reference system to obtain variable data chains composed of the riveting process parameter variables, and then performing riveting control and/or riveting diagnosis by the numerical control riveting system according to the characteristics of the variable data chains.
2. The digitally controlled riveting system based on variable data links of claim 1 wherein the riveting process parameter variables comprise riveting forces and the coordinate reference system comprises a riveting force-time coordinate system;
or, the parameter variables comprise riveting force and riveting stroke, and the coordinate reference system comprises any one or more of a riveting force-time coordinate system, a riveting force-riveting stroke coordinate system, a riveting stroke-time coordinate system or a riveting force-riveting time-riveting stroke coordinate system;
and correspondingly, the variable data chain comprises any one or more of a variable point set of riveting force changing along with time, a variable point set of riveting force changing along with riveting stroke, a variable point set of riveting stroke changing along with time, or a variable point set of riveting force and riveting stroke along with time.
3. The numerically controlled riveting system based on variable data chains according to claim 2, wherein the origin of coordinates 0 of the riveting process parameter variables as the coordinate reference system variable clusters are respectively set as follows:
setting an origin 0 of a riveting process parameter variable riveting Force by taking an origin of an effective Shi Mao load as a reference origin, wherein a measured value of a riveting Force sensor increases linearly in the same direction along with the increase of a riveting load from 0, and the reading of the riveting Force sensor returns to 0 when the Shi Mao load is completely unloaded, wherein the minimum measured value of the riveting Force sensor is 0;
Setting an origin 0 of a riveting process parameter variable riveting Stroke by taking an origin of an effective Shi Mao load as a reference origin, wherein the measured value of a riveting Stroke sensor linearly changes in the same direction along with the axial displacement (rotation angle) of a transmission system, and the riveting Stroke can be a negative value and is used for representing a reverse withdrawal Stroke;
setting an origin 0 of riveting process parameter variable riveting time t by taking the origin of an effective Shi Mao load as a reference origin, wherein the time t is a natural variable;
the rivet force is equal to the pretension threshold and is considered the starting point for the effective Shi Mao load.
4. The numerical control riveting system based on variable data chain according to claim 3, wherein the numerical control riveting system tracks and analyzes riveting process parameter variables of space vectors, and obtains at least one characteristic point to perform riveting control and/or riveting diagnosis according to the characteristic point;
the characteristic points comprise any one or more of an elastic-plastic conversion point Datum, a riveting starting point Fs, a second entity point Pier, a riveting force peak point Fmax, a rebound unloading point Fr and a Shi Mao end point Fe;
the numerical control riveting system divides the standard riveting process into three or four typical stages by identifying each characteristic point of the riveting process, a Forming stage, a Yielding stage, a Setting stage and a fourth typical stage restination stage, wherein:
Forming stage corresponds to self-riveting starting point F s The section reaching the elastic-plastic conversion point Datum is the elastic deformation stage of the riveting fastener under the load;
the YIelding stage corresponds to a section from an elastic-plastic conversion point Datum to a second entity point Pier, and is a plastic deformation upsetting stage of the riveting fastener under the effect of riveting load and constrained by the wall of a hole of a riveting workpiece;
the Setting stage corresponds to the second entity point from Pier to the riveting force peak point F max The section is a plastic deformation upsetting head-second entity upsetting head Preform forming stage of the riveting fastener under the effect of riveting load and constrained by the wall of the hole of the riveting workpiece and the contact surface of the upsetting head;
the response stage corresponds to the riveting force peak point F max To rebound unloading point F r A section, an optimized forming stage for maintaining Shi Mao load of the rivet fastener to eliminate residual stress effects.
5. The numerical control riveting system based on variable data chain according to claim 4, wherein the riveting control performed by the numerical control riveting system according to the characteristics of the variable data chain comprises riveting control in any one or more combination modes of a Dummy test mode, a Parametric Riveting parameter mode, a Adaptive Riveting adaptive mode and a Resume rivet mode;
The riveting diagnosis performed by the numerical control riveting system according to the characteristics of the variable data chain comprises any one or more of a Process diagnosis mode, a Quality diagnosis mode, a Rivet diagnosis mode and a Workpiece diagnosis mode.
6. The variable data chain based numerically controlled riveting system as in claim 5, wherein the control in Parametric Riveting parametric mode is as follows:
SA1, presetting a stop point riveting force peak value Fmax according to an input riveting nut specification material;
SA2, uploading a riveting fastener, starting a power unit of a riveting power mechanism to pretighten the riveting fastener, and monitoring whether the axial force is higher than a pretightening force threshold value in real time by a numerical control riveting system, and setting a coordinate origin to construct a coordinate reference system when the axial force reaches the pretightening force threshold value;
SA3, applying a load by the numerical control riveting system to enter a riveting stroke, monitoring the riveting force or the riveting force and the riveting stroke in real time, and generating a value monitored in real time as a variable cluster of a coordinate reference system to the coordinate reference system;
SA4, monitoring parameter variables of a riveting process in a coordinate reference system, obtaining an elastic-plastic conversion point Datum, comparing the parameter variables with a pre-stored Datum range corresponding to a riveting nut specification material as a riveting process diagnosis reference point, giving a prompt if the Datum exceeds the range, simultaneously automatically switching to an adaptive mode to continue riveting control, and otherwise continuing to execute SA5; indicating error in specification input of rivet nut
SA5 monitoring whether the riveting force in the coordinate reference system reaches the peak value F of the riveting force at the stop point max If yes, automatically cutting off the power supply to finish the riveting action according to the preset, or automatically cutting off the power supply to finish the riveting action after the riveting force is kept for a period of time;
the system pre-stores riveting process functions f (-) corresponding to the riveting nuts of all specifications, the riveting process functions f (-) comprise variable data chains, and in step SA1, corresponding f (-) is obtained based on riveting nut specification materials, so that the riveting force peak value Fmax is determined.
7. The variable data chain based numerically controlled riveting system as in claim 5, wherein the Adaptive Riveting adaptive mode control process is as follows:
the method comprises the steps of SB1, uploading a riveting fastener, starting a power unit of a riveting power mechanism to pretighten the riveting fastener, and setting a coordinate origin to construct a coordinate reference system when a numerical control riveting system monitors whether an axial force is higher than a pretightening force threshold value in real time and reaches the pretightening force threshold value;
SB2, applying a load to enter a riveting stroke by the numerical control riveting system, monitoring the riveting force or the riveting force and the riveting stroke in real time, and generating a value monitored in real time as a variable cluster of a coordinate reference system to the coordinate reference system;
SB3 monitoring the riveting process parameter variable in the coordinate reference system and obtaining an elastic-plastic conversion point Datum, taking the parameter variable as a control reference point, and calculating a riveting force peak value F of the self-adaptive stopping point according to the control reference point Datum max ；
SB4 monitoring parameter variables of riveting process in the coordinate reference system and obtaining a second entity point Pier, indicating to enter a Setting stage after the second entity point Pier is monitored, and when the real-time riveting force reaches a riveting force peak value F max Step SB5 is executed;
SB5, the numerical control riveting system selects to automatically cut off a power supply to finish the riveting action according to the preset, or enters a reporting stage, monitors time and riveting force, controls the riveting force to gradually drop to zero along the set time to cut off the power supply of the motor to finish the riveting action, or keeps the riveting force at the reporting stage to cut off the power supply of the motor to finish the riveting action after the riveting force threshold value reaches the set time;
when the offset is preset, the offset is based on the riveting force peak value F according to the preset experience max Determining an adjustable range of a riveting force threshold value, and executing step SB5 based on the riveting force adjustable range;
in step SB3, where the system is pre-stored with specific functional relationships between rivet nuts of various specifications and the peak value Fmax of the riveting force, datum and the peak value F of the riveting force are determined based on the elastic-plastic transition point Datum max And calculates the riveting force peak value Fmax according to the function relation and Datum.
8. The numerical control riveting system based on variable data chain according to claim 5, wherein the Dummy test mode is used for blank pull test under the working condition that the uploading riveting fastener is not loaded with a riveting workpiece, a specific function relation between the corresponding riveting nut and the optimal riveting force peak value thereof can be obtained through a plurality of blank pull tests, and the riveting process function f (·) of the corresponding riveting nut can be obtained as a reference;
the Resume continuous riveting mode is a strong withdrawal continuous riveting mode under the abnormal interruption working condition in the riveting process, a numerical control riveting system acquires riveting characteristic points in the riveting working process, determines the riveting stage and the forward fastening stroke where the abnormal interruption is located, and provides strong withdrawal protection and continuous riveting control according to the abnormal interruption working condition;
the strong backing protection is that when an abnormal interrupt user forcedly exits, the numerical control riveting system stores interrupt field data, monitors and confirms that the voltage/current of a motor in an exiting stroke is within a permissible range in real time, ensures that the reverse stroke is larger than the sum of the corresponding strokes of the forward fastening stroke and the protection turns, ensures that gap separation exists between the riveting nut and the guide nozzle, and enables the pull rod to continue to exit and be in threaded connection with the riveting nut;
The continuous riveting control is a mortise applying operation which is performed again after the forced withdrawal of the abnormal interruption occurs, and the numerical control riveting system controls the continuous riveting operation according to the interruption position, wherein the continuous riveting operation comprises a continuous riveting operation of the abnormal interruption in a Forming stage, a continuous riveting operation of the abnormal interruption in a YIelding stage and a continuous riveting operation of the abnormal interruption in a Setting stage.
9. The numerically controlled riveting system based on variable data chains as in claim 5, wherein the Process diagnostic model diagnostic Process is as follows:
generating a current riveting process function f '(. Cndot.) in the riveting process, and judging whether a remarkable abnormality exists in the riveting process or not based on a pre-stored riveting process function f' (. Cndot.) and a preset allowable deviation amount Bias thereof according to the consistency of the characteristic vector and/or the change rule of the pre-stored riveting process function f (& cndot.) in the riveting process;
or generating and outputting a riveting characteristic curve which is smoothly subjected to riveting process parameter variables according to the set coordinate origin, standardizing the riveting characteristic curve, comparing and analyzing the riveting characteristic curve with a riveting reference characteristic curve, and using the riveting characteristic vector distance as a similarity representation for judging whether obvious abnormality exists in the riveting process;
or acquiring a riveting characteristic vector, and diagnosing the riveting process by using any one or combination of a plurality of concentrated, off-center, off-state and peak characteristic values based on a statistical analysis method of historical data, wherein the method comprises abnormality detection based on process statistics 6 sigma and/or Box Plot (Box graph) and is used for judging whether obvious abnormality exists in the riveting process;
The pre-stored riveting process function f (,), the riveting reference characteristic curve are obtained through a Dummy test mode of riveting nuts delivered from a batch, or are obtained through a Dummy test mode of one or more riveting nuts in the same batch;
a Quality diagnosis mode, wherein a current riveting process function f' (. Cndot.) is obtained in the riveting work process, a pre-stored corresponding riveting process function f (-) is obtained based on the characteristic points, and whether the riveting Quality problem caused by under riveting/over riveting exists is judged according to the comparison of the two riveting process functions;
the Quality diagnosis mode is also used for judging whether abnormal riveting Process affecting the riveting Quality exists or not through the diagnosis of the riveting working Process on the basis of the Process diagnosis mode;
the diagnostic procedure for the Rivet diagnostic mode is as follows: acquiring a riveting characteristic vector in the riveting process, and judging whether a deviation exists between the riveting characteristic vector and a riveting fastener selected/input by a user or whether the riveting fastener has a significant difference in the riveting process in the same batch based on the material and the specification of the riveting fastener represented by the individual elastic-plastic conversion point of the Datum riveting nut, so as to be used for material mixing diagnosis;
The diagnostic procedure for the Workpiece diagnostic mode is as follows: and acquiring a riveting characteristic vector in the riveting process, and judging whether the thickness of the riveting workpiece exceeds a permissible threshold range or not or whether the thickness of the riveting workpiece has obvious difference in the same batch of riveting work based on the thickness of the riveting workpiece represented by the Datum elastic-plastic conversion point and the Pier second entity point.
10. The numerical control riveting system based on a variable data chain according to any one of claims 1-9, wherein the numerical control riveting system is based on a coordinate reference system, generates and outputs a smoothly riveted characteristic curve of a riveting process parameter variable according to a set origin of coordinates, the riveted characteristic curve describes an association relationship between the riveting process parameter variable in the coordinate reference system, the numerical control riveting system identifies each characteristic point by analyzing the riveted characteristic curve, performs riveting control and/or riveting diagnosis based on the riveted characteristic curve, and divides a standard riveting process into four typical stages based on the riveted characteristic curve;
and the riveting characteristic curve comprises any one or a combination of a plurality of riveting force-riveting stroke curve (F-S), riveting force-time curve (F-t) and riveting stroke-riveting force-riveting time (F-S-t).
11. The digitally controlled riveting system based on variable data link according to claim 10 wherein the variable cluster further comprises a real-time electrical signal that is self-monitored by the system circuit, the digitally controlled riveting system monitors the riveting conditions in real time during the riveting operation, obtains real-time voltage/current of the drive motor, and generates a two-dimensional/three-dimensional extended riveting characteristic curve with the obtained real-time riveting force and/or riveting stroke, comprising any one or a combination of more of an I-t (motor current-riveting time) curve, a V-t (motor voltage-riveting time) curve, an F-I (riveting force-motor current) curve, an F-P (riveting force-motor output power) curve, an S-t (riveting stroke-riveting time) curve, an S-I (riveting stroke-motor current) curve, an S-P (riveting force-riveting stroke-motor current) curve, and an F-S-P (riveting force-riveting stroke-motor output power) curve.
12. The numerical control riveting system based on variable data chain according to any one of claims 1-9, wherein the numerical control riveting system comprises an electric control main board, a storage module and/or a transmission module connected to the electric control main board, a display module and a control key thereon;
The riveting force is obtained through a riveting force sensor, the riveting force sensor is a pressure sensor arranged in a sensor cavity in a power mechanism frame, the riveting power mechanism comprises a main shaft used for connecting a riveting functional component, the main shaft circumferentially movably penetrates through the pressure sensor, a front thrust bearing and a rear thrust bearing are respectively arranged on two sides of the main shaft positioned on the pressure sensor, and when the main shaft bears an axial load, the axial load can be converted into pressure between the front thrust bearing and/or the rear thrust bearing and the pressure sensor through the front thrust bearing and/or the rear thrust bearing;
the riveting stroke is obtained through an angle sensor, the riveting power mechanism comprises a motor and a gearbox, the gearbox drives an output shaft of a main shaft to rotate, and the angle sensor is arranged on the output shaft.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211165834.9A CN117798308A (en) | 2022-09-23 | 2022-09-23 | Numerical control riveting system based on variable data chain |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211165834.9A CN117798308A (en) | 2022-09-23 | 2022-09-23 | Numerical control riveting system based on variable data chain |
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| CN117798308A true CN117798308A (en) | 2024-04-02 |
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| CN202211165834.9A Pending CN117798308A (en) | 2022-09-23 | 2022-09-23 | Numerical control riveting system based on variable data chain |
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| CN (1) | CN117798308A (en) |
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