An intelligent upsetting and riveting method of an automatic drilling and riveting machine based on force-position hybrid control

Abstract

The application discloses an intelligent upsetting and riveting method of an automatic drilling and riveting machine based on force-position hybrid control, and relates to the field of intelligent riveting control.The method comprises the following steps: driving a riveting shaft to feed to a preset approaching area at a first motion speed through a position control mode; triggering seamless switching of the control mode to a force control mode based on dynamic error determination of real-time displacement feedback and a target position; synchronously collecting force signals fed back by a pressure sensor through a distributed real-time I / O system in the force control mode; immediately terminating the feeding motion of the riveting shaft to complete upsetting and riveting forming when the force signals reach a preset threshold of dynamic calibration; and then controlling the riveting shaft to reversely separate from a riveting area at a second motion speed.The application scheme can significantly improve the control precision and stability of the riveting force, effectively suppresses the riveting force fluctuation caused by material deformation or external interference, and thus guarantees the consistency of the upsetting head forming quality and the reliability of the connecting structure.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of intelligent riveting control, in particular to an intelligent upsetting and riveting method of automatic drilling and riveting machine based on force-position hybrid control. BACKGROUND

[0002] Drilling and riveting technology, as a key mechanical connection process in the assembly of aircraft panels in the field of aviation manufacturing, has been widely adopted due to its advantages of light weight, high connection strength, etc. This technology has evolved from manual hammer riveting, pneumatic riveting, etc. to numerical control automatic drilling and riveting. With the continuous improvement of the connection quality requirements of aviation components, achieving high-precision control of riveting force in the riveting process has become a core challenge to improve the consistency of rivet head forming and connection reliability. Traditional numerical control drilling and riveting systems mostly use position closed-loop control, which can achieve high speed and high positioning accuracy, but has significant limitations in force control. Often, the force signal is only used as an auxiliary monitoring parameter, and it is not included in the core control loop, so it is difficult to achieve real-time and accurate regulation and control of the riveting force.

[0003] The existing automatic drilling and riveting method based on position control has the following limitations due to the lack of closed-loop control of the force signal: first, the system cannot dynamically adjust the execution action according to the actual riveting force, which can easily cause the riveting force to deviate from the ideal range due to material deformation, friction and other factors, and further cause quality defects such as excessive riveting or insufficient riveting strength; second, the traditional method lacks a force protection mechanism during the rivet contact stage, and the riveting shaft often still takes displacement as the final target, causing uncontrollable plastic deformation of the rivet or the connecting piece, affecting the forming consistency and fatigue performance; in addition, there is a delay in force detection and response under the existing control architecture, which makes it difficult to meet the high requirements of real-time and synchronization in aviation riveting process, thereby limiting its application potential in high-end manufacturing. Therefore, based on the above problems, the present application proposes an intelligent upsetting and riveting method of automatic drilling and riveting machine based on force-position hybrid control. SUMMARY

[0004] In order to solve the above problems, the purpose of the present application is to provide an intelligent upsetting and riveting method of automatic drilling and riveting machine based on force-position hybrid control, which aims to solve the problem that the existing automatic drilling and riveting machine cannot accurately control the riveting force due to the use of single position control mode during the riveting process, resulting in unstable riveting quality and poor rivet head forming consistency. While ensuring positioning accuracy, the size and application timing of the riveting force are accurately controlled, thereby significantly improving the riveting forming quality and connection reliability, and meeting the demand for high-precision and high-efficiency riveting process in the field of aviation manufacturing.

[0005] In order to achieve the above object, the application provides an intelligent upsetting and riveting method of automatic drilling and riveting machine based on force-position hybrid control, which takes numerical control system as core control unit, integrates length detection device and pressure sensing device to provide high-precision position feedback and real-time force feedback respectively, and through macro program logic judgment, in the process of riveting shaft feeding, firstly adopts position control mode to realize fast positioning to rivet area, and then automatically switches to force control mode, compares riveting force signal collected in real time with preset threshold value to control termination and exit of riveting action, and force signal is transmitted through high-speed synchronous communication interface to ensure system response speed and control precision, so that high-quality intelligent upsetting and riveting process of force-position hybrid control is completed.

[0006] In the first aspect, the application provides an intelligent upsetting and riveting method of automatic drilling and riveting machine based on force-position hybrid control, which comprises:

[0007] The riveting shaft is driven by the position control mode to feed to the preset approach area at a first movement speed;

[0008] Based on dynamic error judgment of real-time displacement feedback and target position, the control mode is triggered to switch to force control mode seamlessly to realize cooperation of high-speed positioning and accurate force control;

[0009] In the force control mode, the force signal fed back by the pressure sensor is synchronously collected through the distributed real-time I / O system to ensure that the collection period of the force signal and the position signal is strictly matched;

[0010] When the force signal reaches the preset threshold value of dynamic calibration, the feeding movement of the riveting shaft is immediately terminated to complete the upsetting and riveting forming, and the riveting force fluctuation caused by material deformation or external interference is inhibited;

[0011] Then the riveting shaft is controlled to reverse and separate from the riveting area at a second movement speed to ensure consistency of upsetting head forming quality and connection reliability.

[0012] Further, the trigger condition of the dynamic error judgment is that the displacement error is lower than the critical tolerance threshold, and the mode switching is realized through precompiled real-time interrupt control logic to ensure that the switching action is completed in a single control period.

[0013] Further, the distributed real-time I / O system adopts isochronous synchronization protocol based on industrial Ethernet to ensure that the collection period of the force signal and the position signal matches the control period of the numerical control system.

[0014] Further, the preset threshold value of dynamic calibration is generated through the following steps:

[0015] In the low-speed contact stage, the cooperative response characteristics of force signal change gradient and micro displacement are synchronously monitored;

[0016] Identify the nonlinear transition point of the force-position response curve, and record the critical force value;

[0017] The preset threshold is generated based on a dynamic compensation mechanism of a safety factor, to ensure that the rivet is in an elastic deformation stage during switching.

[0018] Further, the identification of the nonlinear transition point is based on the fact that the force signal change gradient exceeds the preset gradient threshold, and is accompanied by the detection of micron-level plastic deformation. The threshold calibration is completed before plastic deformation through real-time interrupt logic.

[0019] In a second aspect, the present application also provides an intelligent riveting system of an automatic drilling and riveting machine based on hybrid force-position control, which is based on the method of the first aspect and comprises:

[0020] A numerical control system, a length detection device integrated into the riveting shaft, a pressure sensing device, a distributed real-time I / O system, and a parameter adaptive module;

[0021] The distributed real-time I / O system directly connects the position signal output by the length detection device to the special encoder interface of the numerical control system, and transmits the force signal of the pressure sensing device through an isochronous synchronous real-time communication protocol, to construct a hybrid control architecture of double closed loops of force and position.

[0022] The parameter adaptive module stores multiple sets of calibration parameters corresponding to rivet specifications, and dynamically calls the preset threshold, to realize process adaptability and riveting quality stability.

[0023] Further, the numerical control system is configured with a pre-compiled real-time interrupt control logic for performing dynamic error judgment and mode switching operation, to ensure real-time analysis and response of control instructions.

[0024] Further, the numerical control system is configured as follows:

[0025] Continuously monitor the force signal change gradient in the force control mode;

[0026] When the real-time force value reaches the preset threshold, the riveting shaft is triggered to stop urgently in a single control cycle through the real-time interrupt control logic, to eliminate the defects of over-riveting or insufficient riveting.

[0027] Further, the parameter adaptive module further implements statistical process control of calibration data, including mean filtering processing and standard deviation analysis of the critical force value, and triggers a warning mechanism when data is abnormal, to realize real-time monitoring of rivet material and clamping state.

[0028] Further, the parameter adaptive module performs real-time statistical process control of calibration data, including:

[0029] The critical force values of the same specification rivet obtained by multiple calibrations are subjected to mean filtering processing;

[0030] The standard deviation of the critical force value is calculated and a historical statistical benchmark is established;

[0031] When the single calibration value deviates from the historical statistical benchmark and exceeds the preset tolerance range, a rivet material quality abnormality early warning is triggered, forming a closed-loop quality feedback mechanism.

[0032] The present application takes numerical control system as control center, integrates length detection device and pressure sensing device, respectively provides high-precision position feedback and real-time force signal feedback. The system first adopts position control mode to realize rapid and accurate positioning of riveting shaft during riveting process, automatically switches to force control mode after reaching the preset approach position, controls the timely termination and exit of riveting action by continuously monitoring the riveting force signal and comparing it with the set threshold in real time, and finally realizes high-precision and self-adaptive regulation and control of the whole riveting process.

[0033] The scheme significantly improves the control accuracy and stability of riveting force through double closed-loop hybrid control of force and position, effectively suppresses the riveting force fluctuation caused by material deformation or external interference, thereby ensuring the consistency of the upsetting head forming quality and the reliability of the connected structure. The system has the advantages of high-speed positioning and accurate force control, can adapt to various riveting process requirements, significantly improves the overall quality level and automation degree of the riveting process, and meets the strict requirements of high-end equipment manufacturing field for precision connection technology.

[0034] Advantages

[0035] By implementing the above-mentioned intelligent upsetting and riveting method of automatic drilling and riveting machine based on force-position hybrid control, the following technical effects are achieved:

[0036] (1) The position control and force control are organically integrated into the same riveting process, through seamless switching of the two control modes, the high speed and high positioning accuracy of position control are retained, and the accurate force value adjustment of force control is realized, thereby fundamentally solving the process problems of large riveting force fluctuation and inconsistent forming quality under single control mode.

[0037] (2) By adopting high-speed isochronous synchronous communication interface to integrate force and position sensing information, the force signal and position signal are collected and processed in a very short system cycle, the signal transmission and response delay are greatly reduced, the key hardware foundation for high-precision closed-loop control of riveting process is provided, and the system response speed and control real-time performance are significantly improved.

[0038] (3) Put forward to the material properties and rivet parameters as the basis, combined with low speed contact calibration experiment dynamic threshold setting mechanism, can be in different riveting conditions automatic calibration force control switching point, both avoid riveting force excess lead to structural damage, but also guarantee the riveting process has good process adaptability and stability.

[0039] (4) Relying on the numerical control system macro program to realize the real-time analysis and action decision of control instruction, complete the whole process automation control from rapid feed, force control switching to riveting termination, significantly improve the intelligence and reliability of riveting action, effectively meet the complex process requirements of high quality and high efficiency riveting in aviation manufacturing. BRIEF DESCRIPTION OF DRAWINGS

[0040] In order to make the above-mentioned automatic drilling and riveting machine intelligent riveting method based on force-position hybrid control more obvious and easy to understand, the drawings needed in the specific embodiment of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can be obtained from these drawings without creative labor for those skilled in the art.

[0041] Figure 1 The method flowchart of the present application is shown;

[0042] Figure 2 The principle schematic diagram of the present application is shown. DETAILED DESCRIPTION

[0043] Example 1:

[0044] An automatic drilling and riveting machine intelligent riveting method based on force-position hybrid control is provided, the method flow is shown as Figure 1 , the principle is shown as Figure 2 , including: driving the riveting shaft to the preset approach area with the first motion speed by the position control mode; based on the dynamic error determination of real-time displacement feedback and target position, triggering the control mode to switch to force control mode seamlessly; in the force control mode, synchronously collecting the force signal feedback by the pressure sensor through the distributed real-time I / O system; when the force signal reaches the preset threshold value of dynamic calibration, immediately terminate the feeding motion of the riveting shaft to complete the riveting forming; then control the riveting shaft to reverse away from the riveting area with the second motion speed.

[0045] Specifically as follows.

[0046] Firstly, the control system of the automatic drilling and riveting machine is built. The high-end numerical control system is used as the core control unit. On the riveting shaft, a length detection device and a pressure sensing device are precisely installed. The grating ruler is directly connected to the special encoder interface of the numerical control system as the second measurement system to realize position feedback. The analog output signal of the force sensor is connected to the high-precision signal processing module. The high-precision signal processing module is connected to the numerical control system through PROFINET industrial Ethernet and enables the IRT (isochronous real-time) real-time communication protocol to control the jitter of the entire force signal acquisition and transmission cycle to the microsecond level, ensuring that it is strictly synchronized with the position control cycle, laying the foundation for hybrid control.

[0047] When the riveting process is performed, the host computer issues a riveting instruction. The programmable control logic in the numerical control system starts to execute. First, the system enters the position control mode: the numerical control system drives the servo motor to control the riveting shaft to feed quickly to a preset position very close to the top of the rivet cap according to the high-precision position information fed back by the grating ruler. This stage fully utilizes the high-gain characteristics of the position loop to achieve high speed and accurate positioning.

[0048] When the actual position fed back by the grating ruler and the target position error enter a very small range, the macro program triggers mode switching immediately. The system seamlessly transitions to the force control mode. In this mode, the numerical control system continuously reads and samples the real-time force signal at a high speed through the high-precision signal processing module, and compares it with a preset force threshold. The threshold is pre-calibrated and stored in the system parameters according to the rivet material, diameter and target upset size through offline experiments.

[0049] Once the real-time force value reaches or exceeds the preset threshold, the macro program immediately issues an "emergency stop" instruction in the next control cycle to stop all feed movements of the servo motor. At this time, the rivet upset has been accurately formed. Then, the control logic instructs the riveting shaft to quickly retreat in the reverse direction at a predetermined speed to disengage from the workpiece, completing the entire riveting cycle. Through the precise intervention of the force control mode, the system completely avoids defects such as over-riveting or under-riveting that may occur due to pure reliance on displacement endpoints, ensuring high consistency of riveting quality.

[0050] The same device only uses the traditional position control mode, and the target riveting force is set to 20kN. 500 rivets are continuously riveted under each control mode. The comparison results of riveting accuracy, quality consistency and stability of the force-position hybrid control method compared with the traditional position control method are shown in Table 1.

[0051] Table 1, Comparison results of riveting accuracy, quality consistency and stability

[0052]

[0053] The verification shows that in the case of obtaining similar average error as the above-mentioned embodiment, compared with the traditional position control scheme, the method has a magnitude of improvement in riveting force control precision, upsetting head forming quality consistency and process reliability. Although the single-point riveting cycle is slightly prolonged due to the increase of force control link, the comprehensive quality and efficiency improvement makes it fully applicable to the aviation manufacturing field with strict quality requirements. The experimental results show that compared with the traditional position control scheme, the method has significant advantages in riveting force control precision, upsetting head forming quality consistency and process stability, can effectively suppress the riveting force fluctuation, improve the forming size uniformity, greatly reduce the scrap rate, and realize precise closed-loop control of the riveting process by virtue of the high real-time system response capability, thereby comprehensively improving the reliability, consistency and comprehensive performance of the riveting process, meeting the strict requirements of high-end equipment manufacturing field for precision connection technology.

[0054] Embodiment 2:

[0055] On the basis of the foregoing embodiment, how to adaptively determine and optimize the key force control threshold through a dynamic calibration process to adapt to different rivet specifications and working conditions is emphasized, so as to further enhance the universality and reliability of the system.

[0056] After the equipment is first enabled, the rivet batch or specification is replaced, the system starts the built-in parameter calibration program. The program guides the operator to move the riveting shaft above the workpiece with the new rivet clamped.

[0057] At the beginning of calibration, the system controls the riveting shaft to slowly feed the rivet at a very low speed. In this process, the macro program monitors the change gradient of the force sensor signal in real time at the highest sampling rate. At the same time, the system integrates the position information of the grating ruler to accurately calculate the micro displacement of the riveting shaft.

[0058] When the pressure value monitored by the force sensor appears a nonlinear jump point, and at the same time it is detected that the riveting shaft has a micron-level micro plastic deformation under the condition of continuous feeding, the macro program determines that the rivet has entered the initial plastic deformation stage from the elastic deformation at this time. The program immediately records the instantaneous force value at this critical point, and calculates according to the formula:

[0059]

[0060] In the formula, is the material deformation coefficient, which is used to compensate for nonlinear factors such as plate constraint force and friction loss, The value is dynamically adjusted according to the rivet specification, plate material and surface treatment state, and its typical value range is 0.85~1.15; is the instantaneous force value when plastic deformation occurs; is the yield strength of the rivet material; is the cross-sectional area of the rivet.

[0061] Therefore, the relationship between the instantaneous force value and the rivet material yield strength, rivet diameter and target upset forming size is:

[0062]

[0063] In the formula, is the instantaneous force value.

[0064] Subsequently, the system automatically calculates the force control switching threshold according to the pre-stored algorithm:

[0065]

[0066] In the formula, is the force control switching threshold; is the instantaneous force value.

[0067] This is to ensure that the system switches to force control mode in advance before the rivet is significantly plastically deformed in subsequent formal riveting, thereby absolutely avoiding any pre-damage to the rivet or workpiece. The calculated threshold is automatically written into the system parameter library, bound to the rivet specification, and called for subsequent batch riveting.

[0068] In addition, the system can also perform mean filtering processing on the instantaneous force values of the same specification rivet obtained by multiple calibrations, and record the standard deviation, so as to not only adaptively set the threshold, but also process monitoring on the quality consistency of the rivet itself. If the instantaneous force value found in the calibration is abnormally fluctuated, the system can issue an alarm to the operator, prompting that there may be rivet material or clamping abnormalities.

[0069] By introducing the dynamic calibration and adaptive mechanism, the system described in the present application no longer relies on a fixed and unchanging force threshold, but can self-learn and adjust the core parameters, intelligently adapt to changes in the production process, and realize truly intelligent and high-reliability riveting.

Claims

1. A force-position hybrid control based intelligent upsetting and riveting system of an automatic drilling and riveting machine, characterized in that, Comprise: A numerical control system, a length detection device integrated in a riveting shaft, a pressure sensing device, a distributed real-time I / O system, and a parameter adaptive module; The system is configured to perform the following intelligent upsetting and riveting method: Drive the riveting shaft to feed into a preset approaching area at a first movement speed through a position control mode; Trigger a seamless switch to a force control mode based on a dynamic error determination of real-time displacement feedback and a target position; In the force control mode, synchronously collect force signals fed back by the pressure sensing device through the distributed real-time I / O system; When the force signal reaches a preset threshold value of dynamic calibration, immediately terminate the feeding movement of the riveting shaft to complete the lock riveting forming; Subsequently, control the riveting shaft to reverse and separate from the riveting area at a second movement speed; The distributed real-time I / O system directly connects the position signal output by the length detection device to a special encoder interface of the numerical control system, and transmits the force signal of the pressure sensing device through an isochronous synchronous real-time communication protocol; The parameter adaptive module stores multiple sets of calibration parameters corresponding to rivet specifications, and dynamically calls the preset threshold value when the force signal reaches dynamic calibration.

2. The system according to claim 1, wherein: The trigger condition of the dynamic error determination is that the displacement error is lower than a critical tolerance threshold, and the mode switching is realized through pre-compiled real-time interrupt control logic.

3. The system according to claim 1, wherein: The distributed real-time I / O system adopts an isochronous synchronous protocol based on industrial Ethernet to ensure that the collection period of the force signal and the position signal matches the control period of the numerical control system.

4. The system of claim 1, wherein, The preset threshold value of dynamic calibration is generated by the following steps: In the low-speed contact stage, the cooperative response characteristics of the force signal change gradient and the micro displacement are synchronously monitored; Identify the non-linear transition point of the force-position response curve and record the critical force value; Generate the preset threshold value based on the dynamic compensation mechanism of the safety factor to ensure that the rivet is in the elastic deformation stage when switching.

5. The system according to claim 4, wherein: The identification basis of the non-linear transition point is that the force signal change gradient exceeds a preset gradient threshold value, accompanied by the detection of micron-level plastic deformation.

6. The system according to claim 1, wherein: The numerical control system is configured with pre-compiled real-time interrupt control logic for performing dynamic error determination and mode switching operations.

7. The system of claim 6, wherein, The numerical control system is configured to: Continuously monitor the force signal change gradient in the force control mode; When the real-time force value reaches the preset threshold value, trigger the emergency stop of the riveting shaft within a single control period through the real-time interrupt control logic.

8. The system according to claim 1, wherein: The parameter adaptive module further implements statistical process control of calibration data, including mean filtering processing and standard deviation analysis of the critical force value, and triggers a warning mechanism when the data is abnormal.

9. The system of claim 8, wherein, The parameter adaptive module performs real-time statistical process control of calibration data, including: Mean filtering processing of the critical force value of the same specification rivet obtained through multiple calibrations; Calculate the standard deviation of the critical force value and establish a historical statistical benchmark; When the single calibration value deviates from the historical statistical benchmark and exceeds the preset tolerance range, a rivet material abnormality early warning is triggered.

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