Friction stir welding speed control system and method

Abstract

A friction stir welding speed control system and method, the purpose of which is to achieve the stability of the welding process and the improvement of the quality of the weld joint without direct measurement through temperature and torque sensors. The current and voltage sensor 10 in the control system can feed back the current and voltage of the spindle motor 02 to the data signal acquisition board 11 in real time, and the data signal acquisition board 11 feeds back the collected current and voltage values ​​to the control computer 12 through the electrical signal that can be recognized and read by the computer. The control computer 12 can process the data signal transmitted by the data signal acquisition board 11 in real time to calculate the real-time motor spindle 02 torque, and compare it with the pre-set spindle torque, so as to send out an adjustment signal and transmit it to the workpiece motor driver 13 through the data signal line. The workpiece motor driver 13 can adjust the rotation speed of the workpiece motor 07 in real time, thereby controlling the welding speed of the welding process.

Description

Technical Field

[0001] The invention belongs to the technical field of welding process parameter regulation, and in particular relates to a welding speed control technology in a friction stir process. Background Art

[0002] Friction stir welding is a solid-state connection technology for plate connection. During the welding process, friction heat causes the temperature of the welded part of the material to rise to a plastic state. The main process parameters such as welding speed and stirring head speed directly affect the temperature field in the welding area and the thickness of the plastic layer. The change in the elastic-plastic properties of the material also affects the torque and power of friction. The disclosed invention patents (publication numbers CN 103658965 A and CN 110640300 A) use feedback from temperature or torque sensors to adjust the process parameters of friction stir welding online. In fact, by synchronously monitoring the spindle motor current, voltage and speed, calculating the spindle input power and analyzing the power loss during the welding process, the heating power acting on friction and the dynamic torque of the welding process can also be obtained. From the welding heat input, it can be seen that the stirring head speed is a constant value. If the welding speed is too low, a wider thermal-mechanical affected zone will be generated, which will reduce the joint strength; if the welding speed is too high, the material will not soften enough and loose void defects will easily occur. Therefore, the welding speed as the main parameter needs to be accurately adjusted. For annular closed workpieces with overlapping heating temperature fields during friction stir welding, the degree of softening of the plastic layer in the welding zone is inconsistent, and the welding speed needs to be dynamically adjusted. The present invention does not require a temperature or torque sensor, but directly collects the current and voltage of the spindle motor to calculate the real-time torque and feedback, and makes real-time adjustments to the welding speed, which can improve the stability of the welding process and the quality of the joint welding. Summary of the invention

[0003] The purpose of the present invention is to achieve the improvement of welding process stability and weld joint quality without direct measurement by temperature and torque sensors.

[0004] The present invention is a friction stir welding speed control system and method. The friction stir welding speed control system includes a spindle motor 02, a current and voltage sensor 10, a data signal acquisition board 11, a control computer 12, a workpiece motor driver 13, a workpiece motor 07, and a mechanical transmission device 08. The spindle motor 02 provides the spindle speed required for welding, and the motor inputs current and voltage to realize the spindle constant speed rotation. The spindle motor 02 is fixed on the spindle fixture 01 and mechanically connected to the stirring head fixture 03 so that it rotates synchronously with the spindle motor 02; the current and voltage sensor 10 performs real-time level conversion on the current and voltage electrical signals input to the spindle motor, and transmits them to the data signal acquisition board 11; the current and voltage sensor is connected to the spindle motor 02 through a data signal line, and the other end is connected to the data signal acquisition board 11 through a data signal line; the data signal acquisition board 11 can perform digital discrete processing on continuous voltage and current level signals, and transmit them to the control computer 12. The data signal acquisition board 11 is connected to the current and voltage sensor 10 and the control computer 12 through data signal lines respectively; the control computer 12 can analyze and process the data input by the data signal acquisition board 11, and after comparing with the set value, adjust the pulse frequency and output it to the workpiece motor driver 13. The control computer 12 is connected to the workpiece motor driver 13 and the data signal acquisition board 11 through data signal lines respectively.

[0005] The control method of the friction stir welding speed control system described above specifically includes the following steps:

[0006] Step 1: Initialize the control computer 12 and the data signal acquisition board 11;

[0007] Step 2: Use the current and voltage sensor 10 to collect the idling current and voltage of the spindle motor 02 when no welding is performed, and calculate the idling power of the spindle motor 02 through the control computer 12;

[0008] Step 3: Collect the current and voltage of the spindle motor 02 during welding and calculate its power, subtract the idling power of the spindle motor 02, and obtain the real-time welding friction power. In addition, a linear relationship model between stir friction welding power and welding speed is established;

[0009] Step 4: When the welding friction power value is equal to the power value corresponding to the preset optimized welding speed, the current stir friction welding speed parameters are maintained unchanged; when the stir friction power value exceeds this threshold, according to the preset process specifications, the pulse frequency is reduced, and the speed of the workpiece motor 07 in the welding direction is reduced; when the stir friction power is lower than this threshold, the pulse frequency is increased, and the speed of the workpiece motor 07 in the welding direction is increased; during the welding process, the stir friction power value is continuously fed back to the control computer 12, thereby dynamically adjusting the welding speed to form a closed-loop control to achieve continuous and stable welding.

[0010] The beneficial effects of the present invention are as follows: 1. The spindle motor is an energy output device for stir friction. The spindle motor current and voltage can be directly collected to obtain real-time torque without the need for an external temperature or torque sensor, which dynamically reflects the degree of softening of the plastic layer of the welded metal during the welding process. 2. The real-time torque is obtained and fed back by the spindle motor current and voltage to achieve the adjustment of the welding speed, thereby improving the stability of the welding process and the welding quality of the joint. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a schematic diagram of the control system of the present invention, and the accompanying drawings and corresponding names are: 01-spindle clamping component, 02-spindle motor, 03-stirring head fixture, 04-stirring head, 05-welding workpiece, 06-workbench, 07-workpiece motor, 08-mechanical transmission device, 10-current and voltage sensor, 11-data signal acquisition board, 12-control computer, 13-workpiece motor driver. DETAILED DESCRIPTION

[0012] like Figure 1 As shown, the present invention is a friction stir welding speed control system and method, the friction stir welding speed control system includes a spindle motor 02, a current and voltage sensor 10, a data signal acquisition board 11, a control computer 12, a workpiece motor driver 13, a workpiece motor 07, and a mechanical transmission device 08. The spindle motor 02 provides the spindle speed required for welding, and the motor inputs current and voltage to realize the spindle constant speed rotation. The spindle motor 02 is fixed on the spindle fixture 01 and mechanically connected to the stirring head fixture 03 so that it rotates synchronously with the spindle motor 02; the current and voltage sensor 10 performs real-time level conversion on the current and voltage electrical signals input to the spindle motor, and transmits them to the data signal acquisition board 11; the current and voltage sensor is connected to the spindle motor 02 through a data signal line, and the other end is connected to the data signal acquisition board 11 through a data signal line; the data signal acquisition board 11 can perform digital discrete processing on continuous voltage and current level signals, and transmit them to the control computer 12. The data signal acquisition board 11 is connected to the current and voltage sensor 10 and the control computer 12 through data signal lines respectively; the control computer 12 can analyze and process the data input by the data signal acquisition board 11, and after comparing with the set value, adjust the pulse frequency and output it to the workpiece motor driver 13. The control computer 12 is connected to the workpiece motor driver 13 and the data signal acquisition board 11 through data signal lines respectively.

[0013] In the friction stir welding speed control system described above, the workpiece motor driver 13 can simultaneously output the electric energy required to control the rotation of the workpiece motor 07 by controlling the pulse frequency. The workpiece motor driver 13 is connected to the control computer 12 and the workpiece motor (07) via a data signal line.

[0014] In the friction stir welding speed control system described above, the workpiece motor 07 is driven by the electric energy output by the workpiece motor driver 13 to rotate the motor to achieve direction and speed control. The workpiece motor 07 is connected to the workpiece motor driver 13 through a data signal line and is connected to the mechanical transmission device 08 through a mechanical connection.

[0015] In the friction stir welding speed control system described above, the mechanical transmission device 08 can realize the relative movement between the stirring head 04 and the welding workpiece 05 through mechanical transmission. The mechanical transmission device 08 is connected to the inside of the workbench 06 through gear meshing.

[0016] The control method of the friction stir welding speed control system described above specifically includes the following steps:

[0017] Step 1: Initialize the control computer 12 and the data signal acquisition board 11;

[0018] Step 2: Use the current and voltage sensor 10 to collect the idling current and voltage of the spindle motor 02 when no welding is performed, and calculate the idling power of the spindle motor 02 through the control computer 12;

[0019] Step 3: Collect the current and voltage of the spindle motor 02 during welding and calculate its power, subtract the idling power of the spindle motor 02, and obtain the real-time welding friction power. In addition, a linear relationship model between stir friction welding power and welding speed is established;

[0020] Step 4: When the welding friction power value is equal to the power value corresponding to the preset optimized welding speed, the current stir friction welding speed parameters are maintained unchanged; when the stir friction power value exceeds this threshold, according to the preset process specifications, the pulse frequency is reduced, and the speed of the workpiece motor 07 in the welding direction is reduced; when the stir friction power is lower than this threshold, the pulse frequency is increased, and the speed of the workpiece motor 07 in the welding direction is increased; during the welding process, the stir friction power value is continuously fed back to the control computer 12, thereby dynamically adjusting the welding speed to form a closed-loop control to achieve continuous and stable welding.

[0021] The control method of the friction stir welding welding speed control system described above, the welding speed adjustment method in step 2 is as follows:

[0022] The motor friction torque M(t) and friction heating power P are:

[0023] (1)

[0024] (2)

[0025] in, is the friction coefficient; p(r,t) is the friction pressure; R is the radius of the workpiece; r is the distance from a point on the friction surface of the workpiece to the axis of the workpiece; n(t) is the friction speed;

[0026] Since n(t) is independent of r, then:

[0027] (3)

[0028] The control computer 12 realizes real-time synchronous detection of the stator voltage and current of the spindle motor 02 and the friction speed. First, the input power of the spindle motor 02 is calculated. Then, the heating power acting on the friction welding joint is calculated by analyzing and calculating various power losses in the friction welding process. The dynamic torque of the friction welding process is calculated according to formula (3).

[0029] The control method of the stir friction welding speed control system described above calculates the relationship between torque and welding speed: when the stirring head rotates the welding material at high speed, the current and voltage signals of the spindle motor 02 are collected and fed back to the data signal acquisition board 11 through the current and voltage sensor 10. The data signal acquisition board 11 can summarize and generate data curves to the control computer 12. The control computer 12 can calculate the real-time torque of the spindle motor 02 through software: when the torque of the stirring head 04 exceeds a certain threshold, the welding speed is reduced; when the torque of the stirring head 04 is less than the preset threshold, the welding speed is increased.

[0030] In order to better explain the present invention and facilitate understanding, the technical solutions and effects of the present invention are described in detail below through specific implementation modes in conjunction with the accompanying drawings.

[0031] like Figure 1 As shown, the friction stir welding speed control system of the present invention includes 01-spindle clamping component, 02-spindle motor, 03-stirring head fixture, 04-stirring head, 07-workpiece motor, 08-mechanical transmission device, 10-current and voltage sensor, 11-data signal acquisition board, 12-control computer and 13-workpiece motor driver. The workbench 06 is driven by the workpiece motor 07 to drive the mechanical transmission device 08. The spindle motor 02 is connected to the current and voltage sensor 10 through a data signal line, the current and voltage sensor is connected to the data signal acquisition board 11 through a data signal line, the data signal acquisition board 11 is connected to the control computer 12 through a signal line, and the control computer 12 is connected to the workpiece motor driver 13.

[0032] The friction stir welding speed control method of the present invention specifically comprises the following steps:

[0033] Step 1: Initialize the data signal acquisition board 11 and the serial port, timer and register inside the control computer 12.

[0034] Step 2: Adjust the data signal acquisition board 11 and the control calculation program, record the current and voltage values ​​collected when the spindle is idling without welding, and calculate the corresponding output torque value;

[0035] Step 3: Measure multiple groups of welding speed data through preliminary tests, obtain the torque value of the spindle motor 02 corresponding to the welding speed when the welding area is in the most ideal state, input it into the control computer 12, and determine the torque of the stirring head 03 by measuring the difference between the spindle torque and the torque when the spindle is idling. Use the control computer 12 to set the initial welding speed, and establish a linear relationship model between the spindle motor 02 torque and the welding speed of the stirring head 04 according to the relationship between the welding speed and the spindle motor torque. At the same time, according to the preset ideal welding speed value, calculate the welding speed correction parameter of the stirring head 04 to achieve real-time adjustment of the welding speed during the stir friction welding process; the method for correcting the welding speed is as follows:

[0036] When the stirring head 04 rotates at high speed to weld the welding material 05, the current and voltage acquisition device collects the real-time current and voltage of the spindle motor 02 at a fixed frequency and feeds it back to the data signal acquisition board. The data signal acquisition board can generate a real-time current and voltage image and feed it back to the control computer 12. The control computer 12 calculates the real-time torque of the spindle motor 02 using the collected current and voltage data and obtains the real-time torque of the stirring head 03 by subtracting it from the torque when the spindle motor 02 is idling.

[0037] Step 4: When the torque of the spindle motor 02 is equal to the motor torque corresponding to the preset ideal welding speed, the current spindle rotation speed parameters are maintained unchanged; when the torque of the spindle motor 02 exceeds this threshold, according to the preset process specifications, the speed of the workpiece motor 07 is reduced to reduce the welding speed of the stirring head 04; when the motor torque is lower than the threshold, the speed of the workpiece motor 07 is increased to increase the welding speed of the stirring head 04; the control computer 12 feeds back the adjustment of the welding speed to the numerical control system of the welding equipment, forming a loop control to achieve continuous steady-state welding.

Claims

1. A friction stir welding speed control system, comprising a spindle motor (02), a current and voltage sensor (10), a data signal acquisition board (11), a control computer (12), a workpiece motor driver (13), a workpiece motor (07), and a mechanical transmission device (08), characterized in that: The spindle motor (02) provides the spindle speed required for welding, and the motor inputs current and voltage to realize the constant speed rotation of the spindle; the spindle motor (02) is fixed on the spindle fixture (01) and mechanically connected to the stirring head fixture (03) so that it rotates synchronously with the spindle motor (02); the current and voltage sensor (10) performs real-time level conversion on the current and voltage electrical signals input to the spindle motor, and transmits them to the data signal acquisition board (11); the current and voltage sensor is connected to the spindle motor (02) through a data signal line, and the other end is connected to the data signal acquisition board (11) through the data signal line; the data signal The acquisition board (11) can perform digital discrete processing on continuous voltage and current level signals and transmit them to a control computer (12); the data signal acquisition board (11) is connected to the current and voltage sensor (10) and the control computer (12) through data signal lines respectively; the control computer (12) can analyze and process the data input by the data signal acquisition board (11), and after comparing it with the set value, adjust the pulse frequency and output it to the workpiece motor driver (13); the control computer (12) is connected to the workpiece motor driver (13) and the data signal acquisition board (11) through data signal lines respectively.

2. The friction stir welding speed control system according to claim 1, characterized in that The workpiece motor driver (13) can simultaneously output the electric energy required to control the rotation of the workpiece motor (07) by controlling the pulse frequency; the workpiece motor driver (13) is connected to the control computer (12) and the workpiece motor (07) via a data signal line.

3. The friction stir welding speed control system according to claim 1, characterized in that The workpiece motor (07) is driven to rotate by the electric energy output by the workpiece motor driver (13) to achieve direction and speed control; the workpiece motor (07) is connected to the workpiece motor driver (13) via a data signal line, and is connected to the mechanical transmission device (08) via a mechanical connection.

4. The friction stir welding speed control system according to claim 1, characterized in that The mechanical transmission device (08) can realize the relative movement between the stirring head (04) and the welding workpiece (05) through mechanical transmission; the mechanical transmission device (08) is connected to the inside of the workbench (06) through gear meshing.

5. The control method of the friction stir welding speed control system according to claim 1 is characterized in that: The specific steps include: Step 1: Initialize the control computer (12) and the data signal acquisition board (11); Step 2: using a current and voltage sensor (10) to collect the idling current and voltage of the spindle motor (02) when no welding is performed, and calculating the idling power of the spindle motor (02) through a control computer (12); Step 3: Collect the current and voltage of the spindle motor (02) during welding and calculate its power, subtract the idling power of the spindle motor (02), and obtain the real-time welding friction power; Step 4: When the welding friction power value is equal to the power value corresponding to the preset optimized welding speed, the current stir friction welding speed parameter is maintained unchanged; when the stir friction power value exceeds this threshold, according to the preset process specifications, the pulse frequency is reduced and the speed of the workpiece motor (07) in the welding direction is reduced; when the stir friction power is lower than this threshold, the pulse frequency is increased and the speed of the workpiece motor (07) in the welding direction is increased; during the welding process, the stir friction power value is continuously fed back to the control computer (12), thereby dynamically adjusting the welding speed to form a closed-loop control to achieve continuous and stable welding.

6. The control method of the friction stir welding speed control system according to claim 5, characterized in that: The spindle motor idling power P in step 2 a The relationship with the idling voltage U0 and current I0 is: P a =U0I0 (1) Spindle motor power P during welding in step 3 b The relationship between the spindle motor voltage U1 and current I1 during welding is: P b =U1I1 (2) The calculation method of the real-time power P of the spindle motor is: P=P b -P a =U1I1-U0I0 (3) The real-time power of the spindle motor is related to the friction torque of the stirring head. Ignoring the mechanical transmission and the internal energy loss of the spindle motor, the relationship between the friction torque of the stirring head M(t) and the real-time power P of the spindle motor is: Among them, n(t) is the spindle motor speed.

7. The control method of the friction stir welding speed control system according to claim 5, characterized in that: The relationship between the spindle motor (02) power and welding speed is: When the stirring head rotates the welding material at a high speed, the current and voltage signals of the spindle motor (02) are collected and fed back to the data signal acquisition board (11) through the current and voltage sensor (10). The data signal acquisition board (11) can summarize and generate a data curve to the control computer (12). The control computer (12) can calculate the power of the spindle motor (02) through software: when the power of the spindle motor (02) exceeds a certain threshold, the welding speed is reduced; when the power of the spindle motor (02) is less than a preset threshold, the welding speed is increased.

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