A welding system and method for resistance welding machine double closed loop control

Abstract

The application relates to a welding system and method of double closed-loop control of a resistance welding machine, which realizes real-time collection of secondary current and welding pressure by adding relevant sensors and collection circuits on welding tongs and a welding tong controller, introduces a pressure deviation coefficient in constant current control of a control system, and fully considers the influence of pressure change in the current adjustment process; similarly, a current deviation coefficient is introduced in the welding pressure control method, and the influence of welding current change is fully considered in the pressure adjustment process; the application realizes full-element closed-loop control of a welding process, carries out coupled control of secondary current and welding pressure, can more accurately control the dynamic process of welding spot nugget formation, is a more advanced welding control method, and is more suitable for aluminum alloy materials and application occasions with higher requirements on welding quality.

Description

Technical Field

[0001] This invention belongs to the field of resistance welding machine control technology, and in particular to a welding system and method for resistance welding machine with dual closed-loop control. Background Technology

[0002] According to common knowledge in the field of medium-frequency inverter resistance welding, a medium-frequency inverter resistance welding control system is as follows: Figure 2 As shown, it includes 1-welding controller, 2-transformer, 3-secondary rectifier module, and 4-current output mechanism, also known as electrode; the welding controller integrates 5-IGBT power devices, and the transformer includes primary and secondary sides, also known as primary and secondary windings; typically, the welding controller has 4 groups of IGBTs, such as... Figure 2 IGBTV1, IGBTV2, IGBTV3, and IGBTV4 together form two current output bridge arms, referred to as the upper bridge arm (V1 and V4) and the lower bridge arm (V2 and V3). The current output process is that the upper and lower bridge arms in the controller are turned on at a certain frequency (usually 1KHz), which will form an alternating square wave. This square wave is connected to the primary side of the transformer. The secondary side also outputs a set of alternating square waves with reduced voltage and amplified current. After secondary rectification 3, it is rectified into a set of DC pulse square waves, which are then output through electrode 4 to realize the current output.

[0003] The development of new energy vehicles has driven the application of aluminum alloy materials and their joining methods. Aluminum alloys possess characteristics such as high electrical and thermal conductivity, a large coefficient of thermal expansion, and easy formation of an oxide film on their surface. However, during spot welding of aluminum alloys, the oxide film has a high melting point and is difficult to melt, so high-current, high-pressure welding processes are generally used. After the oxide film melts, the inner aluminum alloy material, with its low melting point and large coefficient of thermal expansion, rapidly forms a weld nugget, which further expands with heating. During the cooling phase, the weld nugget volume rapidly shrinks, easily leading to defects such as porosity or cracks. Therefore, during aluminum spot welding, it is necessary to monitor the changes in the weld nugget in real time and adjust parameters such as current and pressure to ensure the quality of the weld.

[0004] During the expansion process, the weld nugget exerts a reaction force on the welding clamp electrode arm, causing a change in the electrode pressure on the welding clamp electrode arm. Simultaneously, a proportional deformation will occur on the welding clamp electrode arm, such as... Figure 3 As shown. Therefore, how to effectively control the nucleus formation process is one of the urgent problems to be solved. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and propose a welding system and method with dual closed-loop control for resistance welding machines. This invention achieves closed-loop control of all elements of the welding process, and couples the secondary current and welding pressure for control. It can more accurately control the dynamic process of weld nugget formation, and is a more advanced welding control method that is more suitable for aluminum alloy materials and applications with higher requirements for welding quality.

[0006] The technical problem solved by this invention is achieved through the following technical solution:

[0007] A welding system with dual closed-loop control for a resistance welding machine is installed on the resistance welding machine. It includes a secondary constant current control system and a welding pressure control system. The secondary constant current control system is used for real-time adjustment and controllable output of the secondary current Iout, and the welding pressure control system is used for real-time adjustment and controllable output of the welding pressure.

[0008] Furthermore, the secondary constant current control system includes a welding controller and a secondary current sensor. The secondary current sensor is connected to the welding controller, and the welding controller adjusts the secondary current magnitude in real time according to the collected secondary current Isec.

[0009] Furthermore, the welding pressure control system includes: a piezoelectric sensor and a charge amplifier, which are mounted on the welding clamp. The output of the piezoelectric sensor is connected to the input of the charge amplifier, the output of the charge amplifier is connected to the input of the acquisition circuit in the welding controller, the output of the acquisition circuit is connected to the input of the filter circuit in the welding controller, the output of the filter circuit is connected to the input of the control unit in the welding controller, the output of the control unit is connected to the input of the electric cylinder servo driver in the welding controller, and the output of the electric cylinder servo driver in the welding controller is connected to the electric cylinder of the welding clamp.

[0010] A welding method for a resistance welding machine with a dual closed-loop control welding system, comprising secondary constant current control and welding pressure control.

[0011] Furthermore, the secondary constant current control includes the following steps:

[0012] Step 1.1: After receiving the external signal to start welding, the welding controller starts to output current according to the preset process current Iset and output welding pressure according to the preset process pressure Fset.

[0013] Step 1.2: The welding controller collects the secondary current Isec and welding clamp pressure F at a sampling rate of 1KHz;

[0014] Step 1.3: The welding controller adjusts the output current value Iout in real time based on the collected secondary current Isec and welding clamp pressure F.

[0015] Furthermore, the specific implementation method of step 3 is as follows:

[0016] The output current value Ioutp is pre-calculated based on the acquired secondary current Isec:

[0017] Ioutp(n)=Iset(n)+a1*(Iset(n)-Isec(n))

[0018] Where Ioutp(n) is the current value pre-output by the system at time n, Iset(n) is the process current pre-set by the system at time n, Isec(n) is the secondary current of the system at time n, Iset(n)-Isec(n) is the output deviation of the system at time n; a1 is the constant current coefficient, with a value range of 0. <a1<1;

[0019] The final output current value Iout is calculated based on the system's pre-output current value Ioutp and the welding clamp pressure F:

[0020] Iout(n)=Ioutp(n)+b1*Ioutp(n)*(Fset(n)-F(n)) / Fset(n)+c1

[0021] Where Iout(n) is the current value output by the system at time n, Fset(n) is the pre-set process pressure of the system at time n, F(n) is the output welding pressure of the system at time n, (Fset(n)-F(n)) / Fset(n) is the pressure deviation coefficient at time n; b1 is the constant current pressure coefficient, and the value of b1 is in the range of b1<0; c1 is the constant current coefficient, and the value range is 0. <c1<1。

[0022] Furthermore, the welding pressure control includes the following steps:

[0023] Step 2.1: After receiving the external signal to start welding, the welding controller starts to output current according to the preset process current Iset and output welding pressure according to the preset process pressure Fset.

[0024] Step 2.2: The welding controller collects the secondary current Isec and the welding clamp pressure F at a sampling rate of 1KHz;

[0025] Step 2.3: The welding controller adjusts the welding pressure output value Fout in real time based on the collected secondary current Isec and welding clamp pressure F.

[0026] Moreover, the specific implementation method of steps 1.2 and 2.2 is as follows: the welding controller collects the secondary current Isec through the secondary current sensor at a sampling rate of 1KHz, collects the voltage signal Uf through the series piezoelectric sensor, charge amplifier, acquisition circuit and filter circuit, and calculates the welding clamp pressure F through the control unit.

[0027] Furthermore, the specific implementation method of step 2.3 is as follows:

[0028] The pressure value Foutp output by the welding gun of the system is pre-calculated based on the welding gun pressure F:

[0029] Foutp(n)=Fset(n)+b2*(Fset(n)-F(n))

[0030] Where Foutp(n) is the pre-output pressure value of the welding clamp at time n, Fset(n) is the pre-set process pressure of the system at time n, F(n) is the output welding pressure of the system at time n, and Fset(n)-F(n) is the pressure output deviation of the system at time n; b2 is the pressure regulating coefficient, with a value range of 0. <b2<1;

[0031] The final pressure value Fout output by the system welding gun is calculated based on the pre-output pressure value Foutp and the acquired secondary current Isec:

[0032] Fout(n)=Foutp(n)+a2*Foutp(n)*(Iset(n)-Isec(n)) / Iset(n)+c

[0033] Where Fout(n) is the pressure value output by the welding clamp at time n, Iout(n) is the current value output by the system at time n, Iset(n) is the preset process current of the system at time n, (Iset(n)-Isec(n)) / Iset(n) is the current deviation coefficient at time n; a2 is the voltage regulation current coefficient, with a value range of a2<0; c2 is the voltage regulation coefficient, with a value range of 0. <c2<1。

[0034] The advantages and positive effects of this invention are:

[0035] This invention achieves real-time acquisition of secondary current and welding pressure by adding relevant sensors and acquisition circuits to the welding gun and welding gun controller. Furthermore, a pressure deviation coefficient is introduced into the constant current control of the control system to fully consider the impact of pressure changes during current adjustment. Similarly, a current deviation coefficient is introduced into the welding pressure control method to fully consider the impact of welding current changes during pressure adjustment. This invention achieves closed-loop control of all elements of the welding process, coupling the control of secondary current and welding pressure. It can more accurately control the dynamic process of weld nugget formation, making it a more advanced welding control method, more suitable for aluminum alloy materials and applications with higher welding quality requirements. Attached Figure Description

[0036] Figure 1 This is a structural diagram of the welding pressure control system of the present invention;

[0037] Figure 2 This is a structural diagram of a medium-frequency inverter resistance welding control system;

[0038] Figure 3 This is a schematic diagram illustrating the stress on the welding clamp during the spot welding process. Detailed Implementation

[0039] The present invention will be further described in detail below with reference to the accompanying drawings.

[0040] A welding system with dual closed-loop control for a resistance welding machine is installed on the resistance welding machine. It includes a secondary constant current control system and a welding pressure control system. The secondary constant current control system is used for real-time adjustment and controllable output of the secondary current Iout, and the welding pressure control system is used for real-time adjustment and controllable output of the welding pressure.

[0041] The secondary constant current control system includes a welding controller and a secondary current sensor. The secondary current sensor is connected to the welding controller, which adjusts the secondary current magnitude in real time based on the acquired secondary current Isec. The secondary current sensor is mounted on the welding clamp, which includes a secondary transformer, the welding clamp's mechanical structure, electrodes, and related wiring.

[0042] like Figure 1 As shown, the welding pressure control system includes a piezoelectric sensor and a charge amplifier. The piezoelectric sensor and charge amplifier are mounted on the welding clamp. The output of the piezoelectric sensor is connected to the input of the charge amplifier. The output of the charge amplifier is connected to the input of the acquisition circuit in the welding controller. The output of the acquisition circuit is connected to the input of the filter circuit in the welding controller. The output of the filter circuit is connected to the input of the control unit in the welding controller. The output of the control unit is connected to the input of the electric cylinder servo driver in the welding controller. The output of the electric cylinder servo driver in the welding controller is connected to the electric cylinder of the welding clamp. The welding clamp is mounted on a robot.

[0043] A welding method for a resistance welding machine with a dual closed-loop control welding system, comprising secondary constant current control and welding pressure control.

[0044] Secondary constant current control includes the following steps:

[0045] Step 1.1: After receiving the external signal to start welding, the welding controller starts to output current according to the preset process current Iset and output welding pressure according to the preset process pressure Fset.

[0046] Step 1.2: The welding controller collects the secondary current Isec and welding clamp pressure F at a sampling rate of 1KHz.

[0047] The welding controller acquires the secondary current Isec through a secondary current sensor at a sampling rate of 1kHz, acquires the voltage signal Uf through a series piezoelectric sensor, charge amplifier, acquisition circuit and filter circuit, and calculates the welding clamp pressure F through the control unit.

[0048] Step 1.3: The welding controller adjusts the output current value Iout in real time based on the collected secondary current Isec and welding clamp pressure F.

[0049] The output current value Ioutp is pre-calculated based on the acquired secondary current Isec:

[0050] Ioutp(n)=Iset(n)+a1*(Iset(n)-Isec(n))

[0051] Where Ioutp(n) is the current value pre-output by the system at time n, Iset(n) is the process current pre-set by the system at time n, Isec(n) is the secondary current of the system at time n, Iset(n)-Isec(n) is the output deviation of the system at time n; a1 is the constant current coefficient, with a value range of 0. <a1<1。

[0052] The final output current value Iout is calculated based on the system's pre-output current value Ioutp and the welding clamp pressure F:

[0053] Iout(n)=Ioutp(n)+b1*Ioutp(n)*(Fset(n)-F(n)) / Fset(n)+c1

[0054] Where Iout(n) is the current value output by the system at time n, Fset(n) is the pre-set process pressure of the system at time n, F(n) is the output welding pressure of the system at time n, (Fset(n)-F(n)) / Fset(n) is the pressure deviation coefficient at time n; b1 is the constant current pressure coefficient, and the value of b1 is in the range of b1<0; c1 is the constant current coefficient, and the value range is 0. <c1<1。

[0055] Welding pressure control includes the following steps:

[0056] Step 2.1: After receiving the external signal to start welding, the welding controller starts to output current according to the preset process current Iset and output welding pressure according to the preset process pressure Fset.

[0057] Step 2.2: The welding controller collects the secondary current Isec and welding clamp pressure F at a sampling rate of 1KHz.

[0058] The welding controller acquires the secondary current Isec through a secondary current sensor at a sampling rate of 1kHz, acquires the voltage signal Uf through a series piezoelectric sensor, charge amplifier, acquisition circuit and filter circuit, and calculates the welding clamp pressure F through the control unit.

[0059] Step 2.3: The welding controller adjusts the welding pressure output value Fout in real time based on the collected secondary current Isec and welding clamp pressure F.

[0060] The pressure value Foutp output by the welding gun of the system is pre-calculated based on the welding gun pressure F:

[0061] Foutp(n)=Fset(n)+b2*(Fset(n)-F(n))

[0062] Where Foutp(n) is the pre-output pressure value of the welding clamp at time n, Fset(n) is the pre-set process pressure of the system at time n, F(n) is the output welding pressure of the system at time n, and Fset(n)-F(n) is the pressure output deviation of the system at time n; b2 is the pressure regulating coefficient, with a value range of 0. <b2<1。

[0063] The final pressure value Fout output by the system welding gun is calculated based on the pre-output pressure value Foutp and the acquired secondary current Isec:

[0064] Fout(n)=Foutp(n)+a2*Foutp(n)*(Iset(n)-Isec(n)) / Iset(n)+c2

[0065] Where Fout(n) is the pressure value output by the welding clamp at time n, Iout(n) is the current value output by the system at time n, Iset(n) is the preset process current of the system at time n, (Iset(n)-Isec(n)) / Iset(n) is the current deviation coefficient at time n; a2 is the voltage regulation current coefficient, with a value range of a2<0; c2 is the voltage regulation coefficient, with a value range of 0. <c2<1。

[0066] It should be emphasized that the embodiments described in this invention are illustrative rather than limiting. Therefore, this invention includes, but is not limited to, the embodiments described in the specific implementation. Any other implementations derived by those skilled in the art based on the technical solutions of this invention are also within the scope of protection of this invention.

Claims

1. A welding method of a welding system of a double closed loop control of a resistance welder, the welding system used is installed on a resistance welder, characterized in that: The welding system used includes a secondary constant current control system and a welding pressure control system. The secondary constant current control system is used for real-time adjustment and controllable output of the secondary current Iout, and the welding pressure control system is used for real-time adjustment and controllable output of the welding pressure. The secondary constant current control system includes a welding controller and a secondary current sensor. The secondary current sensor is connected to the welding controller, and the welding controller adjusts the secondary current magnitude in real time according to the collected secondary current Isec. The welding pressure control system includes: a piezoelectric sensor and a charge amplifier, which are mounted on the welding clamp. The output of the piezoelectric sensor is connected to the input of the charge amplifier. The output of the charge amplifier is connected to the input of the acquisition circuit in the welding controller. The output of the acquisition circuit is connected to the input of the filter circuit in the welding controller. The output of the filter circuit is connected to the input of the control unit in the welding controller. The output of the control unit is connected to the input of the electric cylinder servo driver in the welding controller. The output of the electric cylinder servo driver in the welding controller is connected to the electric cylinder of the welding clamp. Welding methods, including secondary constant current control and welding pressure control; Step 1.1: After receiving the external signal to start welding, the welding controller starts to output current according to the preset process current Iset and output welding pressure according to the preset process pressure Fset. Step 1.2: The welding controller collects the secondary current Isec and welding clamp pressure F at a sampling rate of 1KHz; Step 1.3: The welding controller adjusts the output current value Iout in real time based on the collected secondary current Isec and welding clamp pressure F; The output current value Ioutp is pre-calculated based on the acquired secondary current Isec: Ioutp(n)=Iset(n)+a1*(Iset(n)-Isec(n)) Where Ioutp(n) is the current value pre-output by the system at time n, Iset(n) is the process current pre-set by the system at time n, Isec(n) is the secondary current of the system at time n, Iset(n)-Isec(n) is the output deviation of the system at time n; a1 is the constant current coefficient, with a value range of 0. <a1<1; The final output current value Iout is calculated based on the system's pre-output current value Ioutp and the welding clamp pressure F: Iout(n)=Ioutp(n)+b1*Ioutp(n)*(Fset(n)-F(n)) / Fset(n)+c1 Where Iout(n) is the current value output by the system at time n, Fset(n) is the pre-set process pressure of the system at time n, F(n) is the output welding pressure of the system at time n, (Fset(n)-F(n)) / Fset(n) is the pressure deviation coefficient at time n; b1 is the constant current pressure coefficient, and the value of b1 is in the range of b1<0; c1 is the constant current coefficient, and the value range is 0. <c1<1。 2. The method of claim 1, wherein: The welding pressure control includes the following steps: Step 2.1: After receiving the external signal to start welding, the welding controller starts to output current according to the preset process current Iset and output welding pressure according to the preset process pressure Fset. Step 2.2: The welding controller collects the secondary current Isec and welding clamp pressure F at a sampling rate of 1KHz; Step 2.3: The welding controller adjusts the welding pressure output value Fout in real time based on the collected secondary current Isec and welding clamp pressure F.

3. A method of welding for a double closed loop controlled welding system of an electric resistance welder according to claim 2, characterized in that: The specific implementation methods of steps 1.2 and 2.2 are as follows: the welding controller collects the secondary current Isec through the secondary current sensor at a sampling rate of 1KHz, collects the voltage signal Uf through the series piezoelectric sensor, charge amplifier, acquisition circuit and filter circuit, and calculates the welding clamp pressure F through the control unit.

4. The welding method of a resistance welding machine with dual closed-loop control according to claim 2, characterized in that: The specific implementation method of step 2.3 is as follows: The pressure value Foutp output by the welding gun of the system is pre-calculated based on the welding gun pressure F: Foutp(n)=Fset(n)+b2*(Fset(n)-F(n)) Where Foutp(n) is the pre-output pressure value of the welding clamp at time n, Fset(n) is the pre-set process pressure of the system at time n, F(n) is the output welding pressure of the system at time n, and Fset(n)-F(n) is the pressure output deviation of the system at time n; b2 is the pressure regulating coefficient, with a value range of 0. <b2<1; The final pressure value Fout output by the system welding gun is calculated based on the pre-output pressure value Foutp and the acquired secondary current Isec: Fout(n)=Foutp(n)+a2*Foutp(n)*(Iset(n)-Isec(n)) / Iset(n)+c2 Where Fout(n) is the pressure value output by the welding clamp at time n, Iout(n) is the current value output by the system at time n, Iset(n) is the preset process current of the system at time n, (Iset(n)-Isec(n)) / Iset(n) is the current deviation coefficient at time n; a2 is the voltage regulation current coefficient, with a value range of a2<0; c2 is the voltage regulation coefficient, with a value range of 0. <c2<1。

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