Method for obtaining and applying relation between riveting force and riveting displacement of electric riveter

Abstract

The invention belongs to the technical field of riveting fastening, and discloses a method for obtaining and applying the relation between riveting force and riveting displacement of an electric riveter, and the method comprises the steps: collecting bus current information through a collection module, and synchronously obtaining the displacement information of a rivet in a riveting process; a pressure sensor is arranged through an experiment to collect actual riveting force information and displacement information; establishing a polynomial mathematical model between the actual riveting force and the bus current of the driving motor through polynomial fitting; and the fitting result of the polynomial mathematical model is converted into the relation between the riveting force and the riveting displacement. According to the method, a motor torque control model is established, a multi-order polynomial fitting method is adopted, the relation between motor bus current and riveting force is obtained, and the riveting force and riveting displacement of a riveter in the riveting process are recorded in real time and transmitted to an upper system; the problems that an electric hand riveter needs to be provided with a force or torque sensor, otherwise, riveting force and riveting displacement in the riveting process cannot be recorded, and riveting quality monitoring and quality backtracking cannot be achieved are solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of riveting and fastening, in particular to the technical field of design and manufacturing of handheld cordless electric tools, and relates to a method for obtaining the relationship between the riveting force and the riveting displacement of an electric riveting gun based on current measurement, specifically a method capable of obtaining the relationship between the riveting force and the riveting displacement during the riveting process in real time and its application in riveting quality monitoring. Background Art

[0002] Rivet connection is a common connection method. Pull rivets are connectors invented using the unidirectional tensile principle of Hooke's law to prevent loosening. They have the characteristics of "once tightened, never loosened". They have good vibration resistance, strong impermeability, high connection strength and easy detection. They can effectively prevent components from loosening during vibration and can be maintenance-free for a long time. They are widely used in aviation, vehicles, construction and other industries.

[0003] Rivet guns can be divided into four types according to the external power: manual, pneumatic, hydraulic and electric. Manual riveting tools are laborious and inefficient to operate. As a solution for alternative power sources, pneumatic and hydraulic were first applied to riveting tools and equipment, and have been developed and popularized to a certain extent. However, riveting tools and equipment with pneumatic and hydraulic as power sources need to be equipped with compressed air or hydraulic pump stations, and there are connecting pipelines between the riveting gun and the power source.

[0004] With the continuous development of battery technology, handheld cordless electric riveting tools powered by batteries have shown excellent portability and do not require external compressed air stations or hydraulic stations, making them particularly suitable for outdoor and high-altitude working conditions. Therefore, batteries are increasingly being used in electric riveting guns.

[0005] Riveting quality inspection is very important for engineering applications. Unqualified riveting directly affects the fastening effect of rivets, which will lead to connection failure and seriously affect the safety of equipment or systems. Intelligent and automated riveting quality inspection is the development trend. Existing riveting tools have developed a large number of pneumatic and hydraulic riveting equipment with riveting process quality inspection technology, which can perform online inspection of riveting quality. However, most of the existing electric riveting equipment, such as electric rivet guns, can only complete simple riveting work. Some can measure the riveting force through tension sensors or torque sensors, or control the riveting process through the motor current. However, there is no application of electric rivet guns that converts motor current into riveting force, nor is there any real-time comparison and analysis of the riveting force and riveting displacement values ​​that occur during the riveting process, and the results are judged, while realizing the function of riveting force and displacement storage and transmission. This function can further realize the monitoring of the riveting process quality and the traceability, storage and management of quality data.

[0006] Patent application: An electric riveting tool, application number 202010067923.4, discloses an electric tool, the ADC channel of which MCU system circuit collects the pressure signal of the pressure sensor and calculates the pulling force value of the riveting gun through corresponding conversion to realize the control of the riveting process.

[0007] Patent application: Electric rivet nut tool with adjustable stroke and riveting force, application number 201811216864.1, discloses an electric rivet nut tool with adjustable stroke and riveting force, whose control processor measures the current value of riveting in real time. When the current value exceeds the preset value, the motor is controlled to reverse and the lead screw returns to the initial position.

[0008] Patent application: A riveting control method for high-strength ring groove rivets, application number 202210676497.3, discloses an electric riveting gun that uses a current control scheme to adjust the riveting force. The motor torque can be controlled by adjusting the input current of the motor, and finally the output tension of the tool can be adjusted.

[0009] Patent application: A direct-drive electric tool, publication number CN205693591U, discloses a controller, a motor, and a setting device, wherein the controller is configured to receive input from the setting device to control the torque and / or speed of the motor, and the output shaft of the motor is directly connected to the working member. The torque control of the motor is realized, and the mechanical overload clutch is eliminated.

[0010] Patent application: A multifunctional intelligent electric tool and its control method, application number 201811549901.0, discloses an electric tool, the output end of the motor used in the tool is connected to the working mechanism, a torque sensor is arranged in the output end of the motor, a magnet is arranged on the outside of the motor, and the motor rotor drives the magnet to rotate, a magnetic encoder is arranged inside the body at the position corresponding to the magnet position, and the magnetic encoder and the torque sensor are electrically connected to the controller.

[0011] The various electric rivet guns currently available do not have the function of recording the riveting force and riveting displacement in real time during the riveting process. In order to obtain the riveting force, some use tension sensors or torque sensors to measure. There are also electric riveting gun patents that use current control to control the riveting force, but they do not give the relationship between the motor current and the riveting force and apply it to the detection of riveting quality. Summary of the invention

[0012] The present invention discloses a method for obtaining the relationship between the riveting force and the riveting displacement of an electric riveting gun based on the shortcomings of the prior art. The purpose of the present invention is to provide a method for obtaining the relationship between the riveting force and the riveting displacement of an electric riveting gun based on the measurement of the motor current and its application in the riveting quality monitoring by establishing a motor digital model and combining experimental research.

[0013] The present invention is achieved through the following technical solutions:

[0014] A method for obtaining and applying the relationship between the riveting force and the riveting displacement of an electric riveting gun, characterized by comprising:

[0015] S1. The busbar current information is collected through the current collection module of the electric rivet gun control system, and the displacement information of the rivet during the riveting process is obtained through the Hall sensor set by the electric rivet gun drive motor at the same time;

[0016] S2. For the same type of electric riveting gun and the same type of rivet, the actual riveting force information during the riveting process of the electric riveting gun is collected through the pressure sensor set up in the experiment, and the displacement information of the rivet during the riveting process is obtained through the Hall sensor set up by the driving motor of the electric riveting gun at the same time;

[0017] S3, using the information relationship obtained in S1 and S2, a polynomial mathematical model between the actual riveting force and the bus current of the driving motor is established through polynomial fitting; ;in: —Riveting force, unit: N; —Polynomial fitting order; —Undetermined coefficients of polynomial; —Bus current, unit: A;

[0018] S4. Convert the fitting result of the polynomial mathematical model into the relationship between riveting force and riveting displacement.

[0019] The electric riveting gun of the present invention comprises a motor, a gear reduction mechanism, a riveting transmission mechanism, a Hall sensor, a gun head fixture and a PCB control board; the PCB control circuit board controls the rotation of the motor, converts the motor output torque into a pulling force in the axial direction of the rivet gun gun head fixture through the gear reduction mechanism and the riveting transmission mechanism, presses the ring metal into the rivet ring groove through the gun head fixture to realize a permanent fastening connection; after riveting into place, the riveting nail is withdrawn to complete the riveting process.

[0020] Furthermore, the PCB control circuit board has a built-in calculation formula for the conversion relationship between the aforementioned riveting force and the driving motor bus current polynomial mathematical model, and generates and stores the riveting force and riveting displacement relationship in real time by obtaining the driving motor bus current and riveting displacement information.

[0021] Furthermore, the Hall sensor is a Hall sensor provided on the motor itself.

[0022] Furthermore, the PCB control board is composed of a control circuit board and a power drive board which are stacked and installed to achieve interference isolation.

[0023] Furthermore, the electric riveting gun is provided with a network transmission module to upload information during the riveting process in real time and store it in a local memory card at the same time.

[0024] Further, for rivets made of aluminum alloy and with a diameter of 6 mm to 8 mm, the relationship between the riveting force and the riveting displacement is fitted using first-order to sixth-order polynomials, and the fitting results of each order polynomial are as follows:

[0025] First order: F=649.856 I -17.016;

[0026] Second order: F=-4.249 I 2 +669.881 I -2.093;

[0027] Third order: F=6.984 I 3 -54.439 I 2 +772.581 I -53.404;

[0028] Fourth order: F=-5.244 I 4 +60.099 I 3 -233.580 I 2 +995.945 I -126.006;

[0029] Fifth order: F=2.849 I 5 -41.421 I 4 +227.715 I 3 -577.757 I 2 +1293.089 I -202.405;

[0030] Sixth order: F=-4.256 I 6 +67.630 I 5 -422.645 I 4 +1317.546 I 3 -2128.422 I 2 +2286.197 I -408.812.

[0031] Further, for rivets made of aluminum alloy and with a diameter of 6mm to 8mm, the relationship between the riveting force and the riveting displacement is obtained by fitting a third-order polynomial, and the measurement accuracy is less than 5%; the third-order polynomial is: F=6.984 I 3 -54.439 I 2 +772.581 I -53.404.

[0032] According to the working principle of a motor, the present invention provides a method for calculating the riveting force of an electric riveting gun based on motor current measurement by establishing a motor digital model and combining test data.

[0033] The present invention can record the riveting force in the riveting process in real time when the electric riveting gun is not equipped with a force sensor, and simultaneously obtain corresponding real-time riveting displacement information by combining the motor displacement information.

[0034] The method of the present invention measures the riveting force without using a force sensor or a torque sensor by optimizing the structure; a digital model is established in the controller and a multiple polynomial fitting algorithm is used to obtain the relationship between the riveting force and the motor current. The current measurement module of the present invention is small in size and low in cost; the Hall sensor carried by the brushless motor itself is directly used in conjunction with the mechanical gear mechanical transmission mechanism and the screw nut to obtain the riveting displacement. No additional displacement sensor is required.

[0035] The present invention is provided with a storage module, such as an SD card, which can store the riveting force and riveting displacement information in real time during the riveting process, thereby realizing riveting quality monitoring and quality backtracking. The wireless transmission module can send the riveting force and riveting displacement information during the riveting process to the upper network system, thereby realizing the management of the working process quality of multiple riveting guns.

[0036] According to the working principle of the motor, the present invention establishes a motor torque control model in the controller, adopts a multi-order polynomial fitting algorithm, obtains the relationship between the motor single-phase bus current and the riveting force, and no longer requires a force / torque sensor. At the same time, the brushless motor Hall sensor outputs angular displacement information to achieve real-time recording of the riveting force and riveting displacement of the riveting gun during the riveting process, and the data can be transmitted to the upper network system through a wireless network. The present invention solves the problem that the electric rivet gun must be equipped with a force or torque sensor, such as a pressure sensor, otherwise it is impossible to record the riveting force and riveting displacement during the riveting process, and it is impossible to achieve riveting quality monitoring and quality backtracking. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is the main component of the electric riveting gun; in the figure, 1 is the Hall sensor, 2 is the riveting transmission mechanism, 3 is the gun head fixture, 4 is the gear reduction mechanism, 5 is the motor, and 6 is the PCB control board;

[0038] Figure 2 1 is a block diagram of the composition of the PCB control board of the embodiment of the present invention; in the figure, HA represents the A-phase signal of the motor Hall position sensor; HB represents the B-phase signal of the motor Hall position sensor; HC represents the C-phase signal of the motor Hall position sensor;

[0039] Figure 3 is a curve showing the relationship between the riveting displacement and the riveting force of an embodiment of the present invention;

[0040] Figure 4 is a curve showing the relationship between the riveting displacement and the motor bus current in an embodiment of the present invention;

[0041] Figure 5 is a first-order fitting curve diagram of an embodiment of the present invention;

[0042] Figure 6 is a comparison curve diagram of fitting of different orders in an embodiment of the present invention;

[0043] Figures 7 to 11 It is a comparison diagram of riveting force curves obtained by collecting rivet calibration force sensors of 5 groups of the same type in Example of the present invention and the third-order current fitting curve. DETAILED DESCRIPTION

[0044] The present invention is further described below in conjunction with specific implementation methods. The specific implementation methods are further descriptions of the principles of the present invention and do not limit the present invention in any way. Technologies that are the same or similar to the present invention do not exceed the scope of protection of the present invention.

[0045] Combined with the attached pictures.

[0046] like Figure 1 As shown, when the electric riveting gun of the embodiment of the present invention is working, the control circuit composed of the PCB control board 6 controls the rotation of the motor 5, and the output torque of the motor 5 is converted into the pulling force in the axial direction of the rivet gun head fixture 3 through the mechanical gear reduction mechanism 4 and the riveting transmission mechanism 2, and the ring metal is pressed into the rivet ring groove through the gun head fixture 3 to achieve permanent fastening connection. After riveting in place, the riveting process is completed.

[0047] The controller of the PCB control board 6 in the embodiment of the present invention pre-sets a motor current-riveting force conversion monitoring control algorithm.

[0048] The study found that when the electric riveting gun is working, the brushless motor needs to start and stop frequently, and reverse, and the motor is in a power generation state when braking, which will generate a high recoil electromotive force. Secondly, the PWM square wave driven motor will change the power state of the winding during commutation, and due to the existence of the motor inductance, the current will not change suddenly, which will cause additional pulse torque and cause the electromagnetic torque to fluctuate. These factors will introduce noise and interference, resulting in increased measurement data errors, possible control system failure, program malfunction, etc.

[0049] In the embodiment of the present invention, the PCB control board 6 is divided into a control circuit board A and a power drive board B. The two boards are stacked and installed in a design manner, which can effectively isolate interference and reduce the size of the control board, making it easier to install it in the handle. For motors with different power requirements, only the power drive board B needs to be replaced to meet the drive requirements. The logic block diagram of the PCB control board 6 in this embodiment is as follows: Figure 2 shown.

[0050] The control circuit board A consists of a power supply, a single-chip controller, a current acquisition module, a riveting process data communication module, a riveting process data storage module, and a rotor position detection module. During the riveting process, the control circuit board A generates a PWM signal according to the rotor position information, controls the power driver board to conduct the MOS three-phase bridge with a certain logic, and drives the motor to rotate. At the same time, the control circuit board A collects current signals in real time through the current acquisition module to realize the control of the riveting process. The riveting process data communication module and the riveting process data storage module send the riveting process data to the riveting quality network management platform and save it to realize the riveting data management and traceability.

[0051] The power driver board B consists of a power supply, a signal isolation module, a half-bridge driver module, an overcurrent protection module, and a MOS three-phase bridge. Since the PWM signal driving capability sent by the control circuit board A is limited and cannot directly drive the high-voltage, high-power MOS circuit, the power driver board B converts it into a driving signal with appropriate amplitude and sufficient current through optocoupler isolation and a half-bridge driver module to control the on and off of the MOS three-phase bridge and drive the brushless motor. In order to prevent the motor and circuit from burning due to special circumstances such as motor stalling, an overcurrent protection module is designed to shut down the drive circuit when the current is too large to achieve safety protection.

[0052] The present invention divides the hardware circuit into a two-board stacking design of a control circuit board A and a power drive board B, which can effectively isolate interference and ensure the normal operation of the system. Moreover, for motors with different power requirements, only the power drive board needs to be replaced to meet the drive requirements, which is convenient for the development of serialized products.

[0053] Usually, the existing riveting displacement can be directly acquired by adding a displacement sensor, or indirectly acquired by adding an encoder to the motor and using the rotor rotation angle. The simplified system of the present invention uses a brushless motor Hall position sensor to monitor the riveting displacement without adding a sensor.

[0054] According to the mechanical structure of the riveting gun, the riveting displacement and the number of Hall position sensor signals have the following relationship:

[0055] In the formula —Riveting displacement (mm); —Total number of Hall position sensor signals; —Number of Hall position sensor signals per rotor rotation; — gear ratio; —Screw lead (mm).

[0056] From the above formula, it can be calculated that each signal pulse of the Hall position sensor corresponds to a riveting displacement of 0.0068 mm, which can achieve the accuracy required for riveting quality judgment.

[0057] The working principle of the application method for obtaining the relationship between the riveting force and the riveting displacement of the electric riveting gun of the present invention is as follows: the single-chip microcomputer controller of the control circuit board A collects the bus current through the current acquisition module, and obtains the riveting force size during the riveting process according to the current and riveting force model established in the controller; at the same time, the Hall sensor 1 is used to obtain the displacement information of the rivet during the riveting process in combination with the mechanical gear reduction mechanism 4 and the riveting transmission mechanism 2. The riveting force and riveting displacement information are stored in the storage module of the machine, and the information is transmitted to the upper network system through the communication module. The riveting force-riveting displacement relationship during the riveting process is used to monitor the reaction riveting quality.

[0058] The electric riveting gun of the present invention does not need a force or torque sensor, but only needs a current acquisition module set on the PCB control board 6 to obtain the riveting force through the current sensor, which is small in size and low in cost. At the same time, no displacement sensor is required, and the Hall sensor 1 carried by the brushless motor 5 itself is directly used to cooperate with the mechanical gear reduction mechanism 4 and the screw nut of the riveting transmission mechanism 2 to obtain the riveting displacement.

[0059] The method for obtaining the relationship between riveting force and riveting displacement is obtained by establishing a mathematical model of a brushless motor.

[0060] From the working principle of electric riveting gun, we know that the electromagnetic torque output by the motor is converted into the riveting force in the direction of the muzzle axis through the gear and screw mechanism, pulling the rivet to achieve riveting. Ignoring stray losses, the relationship between the riveting force and the electromagnetic torque is: (1)

[0061] In the formula, —Riveting force (N); — gear ratio; —Screw lead (mm); — Mechanical efficiency; —Load torque( ).

[0062] Combining the electromagnetic torque formula and the motor motion equation, the mathematical model of the riveting force can be obtained as follows: (2)

[0063] In the formula, —Motor bus current (A), —Motor mechanical angular speed (rad / min), is the torque constant, —Moment of inertia of rotor and load ( ); —Coefficient of friction.

[0064] Since the parameters of the electric riveting gun, such as the mechanical transmission ratio, lead screw, mechanical moment of inertia and motor torque constant, are all constants, it can be seen from formula (2) that the riveting force of the electric riveting gun is a function related to the motor current and motor speed.

[0065] Based on formula (2), the riveting force model of the electric riveting gun can be simplified by controlling the motor speed to be constant. The simplified mathematical model of the riveting force of the electric riveting gun is shown in formula (3), where , They are all constants, so the riveting force is a linear function of the motor current.

[0066] (3)

[0067] In the formula , (N / A); , (N); is the motor bus current (A).

[0068] However, it is difficult to keep the motor speed constant in actual riveting control, and it is difficult to accurately obtain physical quantities such as the mechanical efficiency of the electric riveting gun, the motor torque constant, and the moment of inertia of the mechanical structure. Therefore, there is currently no accurate method to theoretically calculate the riveting force through the current.

[0069] Since the riveting object is a short-tail ring groove rivet of standard specifications, it is a standard part, and the riveting force curve change trend of the riveting process is basically the same. The present invention proposes a polynomial fitting processing algorithm: under the premise of closed-loop control of the speed of the electric intelligent riveting equipment, the pressure sensor is used to collect the actual riveting force, and the riveting force F and the brushless motor bus current are established by the polynomial fitting method. I The polynomial mathematical model between .

[0070] Figure 3 , Figure 4 The riveting displacement, riveting force F and current of a certain type of rivet during the riveting process I Relationship diagram.

[0071] Obtain the riveting displacement, riveting force F, and current of this type of rivet sample I After the relationship data are obtained, the mathematical model of the rivet pulling force of the electric rivet gun and the bus current of the brushless motor is established using the polynomial fitting method.

[0072] Polynomial fitting is a method of approximating a data set using a polynomial function, which can be used to predict missing or future data. When performing polynomial fitting, polynomials of different degrees are used to approximate the data to obtain the best fitting result. The fitting curve is expressed as follows: (4)

[0073] In the formula —Riveting force (N); —Polynomial fitting order; —Undetermined coefficients of polynomial; —Motor bus current (A).

[0074] Figure 5 This is the first-order fitting curve in polynomial fitting. Generally, the higher the polynomial fitting order, the better the fitting degree will be, but if the order is too high, overfitting will occur.

[0075] The embodiment of the present invention is applied to rivets made of aluminum alloy and with a diameter of 6mm to 8mm. The accuracy obtained by using the third-order fitting meets the requirement that the error is less than 5%. When rivets made of other materials such as carbon steel, stainless steel, etc. are used, the relationship between the riveting current and the riveting force is fitted by the same method, and the relationship between the riveting force and the busbar current can be obtained by selecting the appropriate order.

[0076] Table 1 below shows the polynomial fitting results of order 1 to 6 in this embodiment. 2 It is the coefficient of determination of the polynomial fitting, that is, the percentage of change in the dependent variable that can be explained by the fitting model. The higher the order of the polynomial fitting formula, the more sample data can be predicted.

[0077] Table 1 Polynomial fitting results of different orders

[0078]

[0079] Six sets of formulas were obtained by fitting polynomials of different orders. The determination coefficients of the six sets of polynomial fittings were all good, and the riveting force could be accurately calculated by current in the above samples.

[0080] The embodiment of the present invention uses 1-6 order polynomial formulas to calculate the riveting force respectively, and obtains 6 sets of riveting force-displacement curves, such as Figure 6 As shown in the figure. The black curve in the figure is the actual riveting force-displacement curve obtained by collecting the pressure sensor signal, and the other curves are 6 groups of calculated riveting force-displacement curves. It can be seen from the figure that polynomial formulas of different orders can restore the riveting force through current to a certain extent.

[0081] The result obtained by selecting the third-order polynomial in the embodiment of the present invention can meet the measurement accuracy of 5% of the electric riveting gun.

[0082] The following uses a specific implementation process detection as an example to verify and illustrate the application method of the present invention.

[0083] A certain type of aluminum alloy 6mm short-tail rivet was used to carry out riveting tests to verify the multi-order polynomial fitting algorithm.

[0084] In this embodiment, a total of 5 groups of riveting experiments were carried out; 5 groups of a certain type of 6mm short-tail rivets were used for rivet pulling tests, and the rivet pulling force calculated by current was obtained by fitting the rivet pulling current with a third-order polynomial, and compared and analyzed with the rivet pulling force collected by the calibrated force sensor.

[0085] The results are as follows Figures 7 to 11 As shown, Figures 7 to 11 This is a comparison diagram of the riveting force curves obtained by the calibration force sensor of the same type of rivets in the embodiment of the present invention and the third-order busbar current fitting curve; the solid line in the figure is the riveting force measured by the force sensor, and the dashed line is the riveting force calculated by the third-order polynomial fitting based on the busbar current collected during the riveting process. The riveting process begins at about 12.5mm, and the front part is the gap elimination process. The riveting force calculated by the third-order polynomial fitting can better describe the actual riveting force measured by the force sensor during the riveting process, proving that it is accurate to use the third-order polynomial to fit the actual riveting force.

Claims

1. A method for obtaining and applying the relationship between the riveting force and the riveting displacement of an electric riveting gun, characterized in that include: S1. The busbar current information is collected through the current collection module of the electric rivet gun control system, and the displacement information of the rivet during the riveting process is obtained through the Hall sensor set by the electric rivet gun drive motor at the same time; S2. For the same type of electric riveting gun and the same type of rivet, the actual riveting force information during the riveting process of the electric riveting gun is collected through the pressure sensor set up in the experiment, and the displacement information of the rivet during the riveting process is obtained through the Hall sensor set up by the driving motor of the electric riveting gun at the same time; S3, using the information relationship obtained in S1 and S2, a polynomial mathematical model between the actual riveting force and the bus current of the driving motor is established through polynomial fitting; ;in: —Riveting force, unit: N; —Polynomial fitting order; —Undetermined coefficients of polynomial; —Bus current, unit: A; S4. Convert the fitting result of the polynomial mathematical model into the relationship between riveting force and riveting displacement.

2. The method for obtaining and applying the relationship between the riveting force and the riveting displacement of an electric riveting gun according to claim 1, characterized in that: The electric riveting gun comprises a motor, a gear reduction mechanism, a riveting transmission mechanism, a Hall sensor, a gun head fixture and a PCB control board; the PCB control circuit board controls the rotation of the motor, converts the motor output torque into a pulling force in the axial direction of the rivet gun gun head fixture through the gear reduction mechanism and the riveting transmission mechanism, and presses the ring metal into the rivet ring groove through the gun head fixture to achieve a permanent fastening connection; after riveting into place, the riveting nail is withdrawn to complete the riveting process.

3. The method for obtaining and applying the relationship between the riveting force and the riveting displacement of an electric riveting gun according to claim 2, characterized in that: The PCB control circuit board has a built-in conversion relationship between the obtained riveting force and the driving motor bus current polynomial mathematical model, and generates and stores the riveting force and riveting displacement relationship in real time by obtaining the driving motor bus current and riveting displacement information.

4. The method for obtaining and applying the relationship between the riveting force and the riveting displacement of an electric riveting gun according to claim 3, characterized in that: The Hall sensor is a Hall sensor provided on the motor itself.

5. The method for obtaining and applying the relationship between the riveting force and the riveting displacement of an electric riveting gun according to claim 3, characterized in that: The PCB control board is composed of a control circuit board and a power drive board which are stacked and installed to achieve interference isolation.

6. The method for obtaining and applying the relationship between the riveting force and the riveting displacement of an electric riveting gun according to claim 3, characterized in that: The electric riveting gun is provided with a network transmission module, which uploads the information in the riveting process in real time and stores it in a local memory card at the same time.

7. The method for obtaining and applying the relationship between the riveting force and the riveting displacement of an electric riveting gun according to any one of claims 1 to 6, characterized in that: For rivets made of aluminum alloy and with a diameter of 6mm to 8mm, the relationship between the riveting force and the riveting displacement is fitted using first-order to sixth-order polynomials. The fitting results of each order of polynomials are as follows: First order: F=649.856 I -17.016; Second order: F=-4.249 I 2 +669.881 I -2.093; Third order: F=6.984 I 3 -54.439 I 2 +772.581 I -53.404; Fourth order: F=-5.244 I 4 +60.099 I 3 -233.580 I 2 +995.945 I -126.006; Fifth order: F=2.849 I 5 -41.421 I 4 +227.715 I 3 -577.757 I 2 +1293.089 I -202.405; Sixth order: F=-4.256 I 6 +67.630 I 5 -422.645 I 4 +1317.546 I 3 -2128.422 I 2 +2286.197 I -408.

812.

8. The method for obtaining and applying the relationship between the riveting force and the riveting displacement of an electric riveting gun according to claim 7, characterized in that: The relationship between the riveting force and the riveting displacement is obtained by fitting a third-order polynomial, and the measurement accuracy is less than 5%; the third-order polynomial fitting result relationship is: F=6.984 I 3 -54.439 I 2 +772.581 I -53.404。

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