KR101858741B1 - Method of controlling power of spot weldng system and spot weldng system using thereof - Google Patents

Abstract

A power control method of a spot welding system and a spot welding system using the same are provided. A spot welding system includes a welding electrode and a power supply for providing desired power to the welding electrode by controlling the inverter module, the spot welding system comprising: a detecting module for detecting voltage and current provided to the welding electrode; A current correction value calculation module for calculating a current to be applied to the welding electrode at a detected voltage and a preset target power and for calculating a current correction value corresponding to an error between the calculated current and the detected current; A control signal generation module for generating a switch control signal for driving the inverter module according to the calculated current correction value; And a switch driving module for controlling the inverter module according to the generated switch control signal to provide the desired target power to the welding electrode. This not only makes it possible to control the power, but also has a technical effect to consider the variation of the dynamic resistance.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spot welding system,

The present invention relates to a method and system for controlling the power of an inverter type DC spot welding system among resistance welding machines that can be used in a vehicle assembly line or the like.

Generally, the inverter type DC spot welding is a type of electric welding in which two metal plates are laid out and then sandwiched between the lower welding electrodes and pressure is applied and a large current is flowed using an inverter module . Such spot welding is used in various fields such as automobile body assembly line and thin plate joining process of electronic device production process.

 Especially, in the body assembly line of automobiles, various materials such as high strength steel and aluminum alloy are used to lighten the body, and one of the problems of these materials is poor weldability. Various welding techniques have been developed to solve these problems.

One such welding technique is constant current controlled spot welding. The spot welding of the constant current control method is a method of controlling the current flowing through the welding electrode to a constant current having a constant value. However, in the case of such a constant current control method, only the current can be controlled without considering the variation of the voltage applied to the welding electrode, and the power control is impossible. Further, since the fluctuation of the dynamic resistance of the welding electrode can not be taken into account, the weldability is deteriorated, and it is difficult to secure various data such as dynamic resistance and electric power.

According to one embodiment of the present invention, there is provided a power control method for a spot welding system that enables power control of an inverter type DC spot welding system and a spot welding system using the same.

According to another embodiment of the present invention, there is provided a power control method for a spot welding system capable of securing various data such as dynamic resistance and power amount, taking into account the variation in dynamic resistance of the welding electrode, and a spot welding system using the method .

According to the first embodiment of the present invention,

A spot welding system comprising: a welding electrode; and a power supply for providing a desired target power to the welding electrode by controlling an inverter module,

A voltage detecting module for detecting a voltage supplied to the welding electrode;

A current correction value calculation module for calculating a current correction value to be applied to the welding electrode from a voltage detected by the voltage detection module and a predetermined target power;

A control signal generation module for generating a switch control signal for driving the inverter module according to the calculated current correction value; And

And a switch driving module for controlling the inverter module according to the generated switch control signal to provide the target electric power to the welding electrode.

Here, the voltage detection module may include:

And a low-pass filter for low-pass filtering the detected voltage.

Further, in the spot welding system,

A current detection module for detecting a current provided to the welding electrode;

A power calculation module for calculating a current power provided to the welding electrode from the detected voltage and current; And

And a display module for displaying at least one of the calculated current power, the detected voltage and current, the resistance calculated from the detected voltage and current, and the amount of power of the current power.

In addition,

Constant power having a constant value or variable power capable of being variable.

In addition,

A first rectification module for rectifying an input AC power;

A capacitor module for converting AC power rectified by the first rectification module to DC power;

An inverter module including a plurality of switching elements for switching the DC power converted by the capacitor module according to the switch control signal;

A transformer module for stepping up or down the power source switched by the inverter module; And

And a second rectification module for rectifying a power source that is boosted or stepped down by the transformer module.

According to the second embodiment of the present invention,

A power supply for supplying a desired target power to the welding electrode by controlling the inverter module,

Detecting a voltage provided to the welding electrode;

Calculating a current correction value to be applied to the welding electrode from the detected voltage and a predetermined target power;

Generating a switch control signal for driving the inverter module according to the calculated current correction value; And

And controlling the inverter module according to the generated switch control signal to provide the target electric power to the welding electrode.

Further, the step of detecting the voltage may include:

And low-pass filtering the detected voltage.

In the power control method,

Detecting a current provided to the welding electrode;

Computing current power provided to the welding electrode from the detected voltage and current; And

The method may further include displaying at least one of the calculated current power, the detected voltage and current, the resistance calculated from the detected voltage and current, and the amount of power of the current power.

In addition,

Constant power having a constant value or variable power capable of being variable.

In addition,

A first rectification module for rectifying an input AC power;

A capacitor module for converting the AC power rectified by the first rectification module to DC power;

An inverter module including a plurality of switching elements for switching the DC power converted by the capacitor module according to the switch control signal;

A transformer module for stepping up or down the power source switched by the inverter module; And

And a second rectification module for rectifying a power source that is boosted or stepped down by the transformer module.

According to one embodiment of the present invention, there is a technical effect that not only power control is possible by detecting a voltage provided to a welding electrode, but also a variation in dynamic resistance can be considered.

Further, according to another embodiment of the present invention, there is a technical effect of securing and displaying diverse data such as dynamic resistance and power amount.

1 is a block diagram of a spot welding system according to an embodiment of the invention.
2 is a flowchart for explaining a power control method of a spot welding system according to an embodiment of the present invention.
FIG. 3A is a graph showing measured actual power when the target power is set to the constant power according to an embodiment of the present invention. FIG.
FIG. 3B is a graph showing the detected voltage, current, and dynamic resistance when the target power is set to the constant power according to an embodiment of the present invention. FIG.
FIG. 4A is a graph showing measured actual power when the target power is set as a variable power according to an embodiment of the present invention. FIG.
FIG. 4B is a graph showing the detected voltage, current, and dynamic resistance when the target power is set to a variable power in accordance with an embodiment of the present invention. FIG.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, the embodiments of the present invention can be modified into various other forms, and the scope of the present invention is not limited to the embodiments described below. The shape and the size of the elements in the drawings may be exaggerated for clarity and the same elements are denoted by the same reference numerals in the drawings.

1 is a block diagram of a spot welding system according to an embodiment of the invention. A spot welding system according to an embodiment of the present invention includes a welding electrode 105 and a power supplier 100 to 104 for providing desired power to the welding electrode 105 by controlling the inverter module 102 A spot welding system comprising: a detection module (110) for detecting a voltage and a current provided to a welding electrode (105); and a current calculation unit for calculating a current correction value to be applied to the welding electrode A control signal generation module 114 for generating a switch control signal for driving the inverter module 102 in accordance with the calculated current correction value and a control signal generation module 114 for controlling the inverter module 102 according to the generated switch control signal, To provide a desired target power to the welding electrode 105, by controlling the welding current. Further, according to one embodiment of the present invention, the spot welding system includes a power calculation module 111 for calculating the current power supplied to the welding electrode from the detected voltage and current, and a power calculation module 111 for calculating the calculated current power, A resistance calculated from the detected voltage and current, and a power amount of the current power.

Hereinafter, a spot welding system according to an embodiment of the present invention will be described in detail with reference to FIG.

1, a power supplier 100 to 104 includes a first rectifier module 100, a capacitor module 101, an inverter module 102, a transformer module 103, and a second rectifier module 104 ).

The first rectifier module 100 of the power supplies 100 to 104 includes a plurality of diodes and is capable of rectifying the input three-phase AC power. The rectified AC power can be transmitted to the capacitor module 101.

Among the power supplies 100 to 104, the capacitor module 101 may include one or more capacitors, and the rectified AC power received from the first rectification module 100 may be smoothed and converted into DC power. The converted DC power may be transmitted to the inverter module 102.

Among the power supplies 100 to 104, the inverter module 102 includes a plurality of switching elements, for example, a field effect transistor (FET), an insulated gate bipolar transistor (IGBT) And can be switched according to an applied switch control signal.

Meanwhile, among the power supplies 100 to 104, the transformer module 103 may include a primary winding 103a and a secondary winding 103b, and the primary winding 103a and the secondary winding 103b The power source switched by the inverter module 102 can be stepped up or stepped down according to the winding ratio. The step-up or step-down power supply can be delivered to the second rectification module 104.

The second rectifier module 104 of the power supplies 100 to 104 may include a plurality of diodes and may rectify the step-up or step-down power supplied from the transformer module 103. The rectified power can be supplied to the welding electrode 105. The base material S composed of two metal plates between the welding electrodes 105 is bonded by the power supply provided to the welding electrode 105. [

On the other hand, in order to control the power of the power supplies 100 to 104 described above, according to an embodiment of the present invention, the power control apparatuses 110 to 115 may be included. The power control devices 110 to 115 include a detection module 110, a power calculation module 111, a display module 112, a current correction value calculation module 113, a control signal generation module 114, And may include a driving module 115.

The detection module 110 of the power control devices 110 to 115 may include a current detection unit 110a and a voltage detection unit 110b. The current detection unit 110a may be configured to detect a current flowing through the welding electrode 105, The voltage provided to the welding electrode 105 can be detected through the voltage detection unit 110b. The detected voltage and current may be transmitted to the power calculation module 111. According to one embodiment of the present invention, the current detecting unit 110a and the voltage detecting unit 110b may further include a low-pass filter for obtaining a more stable voltage and current by low-pass filtering the detected voltage and current, respectively .

The power calculation module 111 of the power control devices 110 to 115 calculates the current power supplied to the welding electrode 105 from the voltage and current detected by the detection module 110 as shown in the following Equation 1 have.

[Equation 1]

P _{n -1} = V _{n -1} x I _{n -1}

Where P _{n -1} is the calculated current power, V _{n - 1} is the detected voltage, and I _{n - 1} is the detected current. In addition, the power calculation module 111 can calculate the dynamic resistance and the power amount (also referred to as an 'input heat amount') from the detected voltage and current as shown in Equation (2) below.

&Quot; (2) "

R _{n -1} = V _{n -1} / I _{n -1} , Q _{n -1} = V _{n -1} × I _{n -1} × t

Where R _{n -1} is the current calculated resistance, Q _{n - 1} is the current calculated power, and t is the time.

The calculated dynamic resistance, current power, and power amount may be transmitted to the current correction value calculation module 111 and the display module 112 together with the detected voltage and current.

The display module 112 of the power control apparatuses 110 to 115 controls the current power calculated by the power calculation module 111, the voltage and current detected by the detection module 110, A resistance, and an amount of electric power can be stored and displayed.

The current correction value calculation module 113 of the power control apparatuses 110 to 115 calculates the current correction value from the voltage V _{n -1} detected by the detection module 110 and the preset target power P _n In the next step, the current correction value I _n to be applied to the welding electrode 105 is calculated.

&Quot; (3) "

I _n = P _n / V _{n -1}

Here, I _n denotes a current correction value, P _n denotes a target power, and V _{n -1} denotes a detected current voltage. The calculated current correction value may be transmitted to the control signal generation module 114. The above-described target power may include constant power (see FIG. 3A) or variable power (see FIG. 4A) having a constant value.

The above-described target electric power can be given one by one per cycle. For example, assuming that the welding is performed for 300 ms, the target power can be given in total of 600, one for each 0.5 ms. Accordingly, a total of 600 current correction values can be calculated, and thus a total of 600 inverter modules 102 can be controlled.

Meanwhile, the control signal generation module 114 of the power control devices 110 to 115 may generate a switch control signal for driving the inverter module 102 according to the calculated current correction value. The generated switch control signal may be transmitted to the switch driving module 115. The switch control signal may be, for example, a pulse width modulation (PWM) signal. Specifically, the control signal generation module 114 may generate a PWM signal proportional to the magnitude of the current correction value. For example, if the current correction value is large, the pulse width of the PWM signal becomes large. If the current correction value becomes small, The switch control signal can be generated so that the pulse width becomes smaller.

The switch driving module 115 of the power control devices 110 to 115 controls the inverter module 102 in accordance with the switch control signal received from the control signal generating module 114, And a switch drive module 115 that provides a target power.

2 is a flowchart for explaining a power control method of a spot welding system according to an embodiment of the present invention. On the other hand, FIG. 3A shows the measured current power when the target power is set to the constant power according to the embodiment of the present invention, and FIG. 3B shows the current power when the target power is set to the constant power according to the embodiment of the present invention And the detected voltage, current, and dynamic resistance. 4A is a graph showing measured actual power when a target power is set to a variable power in accordance with an embodiment of the present invention and FIG. Current, and dynamic resistance.

Hereinafter, a power control method of a spot welding system according to an embodiment of the present invention will be described in detail with reference to FIG. 1 to FIG.

Referring to Figs. 1 and 2, in step S200, the detection module 110 can detect a voltage and a current provided to the welding electrode 105. Fig. The detected voltage and current may be transmitted to the power calculation module 111. According to one embodiment of the present invention, the current detecting unit 110a and the voltage detecting unit 110b may further include a low-pass filter for obtaining a more stable voltage and current by low-pass filtering the detected voltage and current, respectively .

In step S201, a current correction value calculation module 113 to a voltage (V _{n -1)} and a preset target power (P _n) to the welding electrode 105 is detected by the detection module 110, as shown in equation (1) Lt; RTI ID _{= 0.0} &_gt; I _n &_lt; / _RTI >

[Equation 1]

I _n = P _n / V _{n -1}

Here, I _n denotes a current correction value, P _n denotes a target power, and V _{n -1} denotes a detected current voltage. The calculated current correction value may be transmitted to the control signal generation module 114. The above-described target power may include constant power (see FIG. 3A) or variable power (see FIG. 4A) having a constant value.

In step S202, the control signal generation module 114 may generate a switch control signal for driving the inverter module 102 in accordance with the calculated current correction value. The generated switch control signal may be transmitted to the switch driving module 115. The switch control signal may be, for example, a pulse width modulation (PWM) signal. Specifically, the control signal generation module 114 may generate a PWM signal proportional to the magnitude of the current correction value. For example, if the current correction value is large, the pulse width of the PWM signal becomes large. If the current correction value becomes small, The switch control signal can be generated so that the pulse width becomes smaller.

Finally, in step S203, the switch driving module 115 controls the inverter module 102 in accordance with the switch control signal received from the control signal generating module 114, thereby providing a desired target power to the welding electrode 105 And a switch driving module 115.

The above-described steps 200 to 203 may be executed once for one cycle (for example, 0.5 ms).

On the other hand, according to the embodiment of the present invention, the power calculation module 111 can calculate the current power supplied to the welding electrode 105 from the voltage and current detected by the detection module 110. [ In addition, the power calculation module 111 can calculate the dynamic resistance and the power amount from the detected voltage and current, and the calculated dynamic resistance, current power, and power amount are calculated together with the detected voltage and current in the current correction value calculation module 111 and the display Module 112, as shown in FIG. Thereafter, the display module 112 displays the current power calculated by the power calculation module 111, the voltage and current detected by the detection module 110, the dynamic resistance calculated from the detected voltage and current, One or more may be stored and displayed.

FIG. 3A shows the measured current power when the target power is set to the constant power according to the embodiment of the present invention, and FIG. 3B shows the detected current power when the target power is set to the constant power according to the embodiment of the present invention Voltage, current, and dynamic resistance.

As shown in FIG. 3A, when the target power is set as the constant power, it can be seen that the current power 300 is controlled almost constantly with time by the power control method according to the embodiment of the present invention have. As shown in FIG. 3B, when the target power is set to the constant power, it can be seen that the current 301 is fluctuating to maintain the constant power when the voltage 302 is fluctuated. In addition, reference numeral 303 denotes a copper resistance which can be calculated from a voltage and a current.

4A shows measured actual power when the target power is set to a variable power according to an embodiment of the present invention, and FIG. 4B shows a case where the target power is set to a variable power according to an embodiment of the present invention And the detected voltage, current, and dynamic resistance. Here, the variable power is a power capable of varying the target power over a multistage over time, and the target power is set in two steps in Fig. 4A.

As shown in FIG. 4A, when the target power is set to two-stage variable power, it can be seen that the current power 400 is changed in two steps by the power control method according to the embodiment of the present invention. Further, as shown in FIG. 4B, when the target power is set to the variable power, it can be seen that the current 401 is changed to maintain the target power when the voltage 402 is changed. In addition, reference numeral 403 denotes a copper resistance which can be calculated from a voltage and a current.

As described above, according to the embodiment of the present invention, there is a technical effect that not only the power provided by detecting the voltage provided to the welding electrode can be controlled but also the variation of the dynamic resistance can be taken into consideration. Further, according to another embodiment of the present invention, there is a technical effect of securing and displaying diverse data such as dynamic resistance and power amount.

According to one embodiment of the present invention as described above, the current correction value calculation module 113 of FIG. 1 is a detection module 110, the voltage detected by the (V _{n -1)} and a preset target power as shown in Equation 3 The current correction value I _n to be applied to the welding electrode 105 in the next step is calculated using the current correction value P _n . However, the present invention is not limited thereto.

For example, the current correction value calculation module 113 of FIG. 1 may be implemented as a fuzzy controller.

Specifically, the current correction value calculation module 113 of FIG. 1 receives the current power calculated according to Equation (1) from the power calculation module 111, and generates an error power of the received current power and a predetermined target power can do. The power calculation module 111 may then operate as a fuzzy controller to generate a current correction value from the generated error power. Specifically, the power calculation module 111 can generate the current correction value from the error power based on the fuzzy logic. The generated current correction value may be transmitted to the control signal generation module 114 of FIG. 1. The control signal generation module 114 generates a switch control signal for driving the inverter module 102 according to the received current correction value . The generated switch control signal may be transmitted to the switch driving module 115. The switch control signal may be, for example, a pulse width modulation (PWM) signal. Specifically, the control signal generation module 114 may generate a PWM signal proportional to the magnitude of the current correction value. For example, if the current correction value is large, the pulse width of the PWM signal becomes large. If the current correction value becomes small, The switch control signal can be generated so that the pulse width becomes smaller. As described above, in the case of generating the current correction value based on the fuzzy theory, the functions of the other components except for the current correction value calculation module 113 are the same as those described above, so that a separate explanation will be omitted.

The present invention is not limited to the above-described embodiments and the accompanying drawings. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims, .

100: first rectification module 101: capacitor module
102: inverter module 103: transformer module
104: second rectification module 105: welding electrode
S; Base material 110: Detection module
110a: current detection module 110b: voltage detection module
111: Power calculation module 112: Display module
113: current correction value calculation module 114: control signal generation module
115: Switch driving module

Claims (10)

A spot welding system comprising: a welding electrode; and a power supplier for providing a desired target power to the welding electrode by controlling an inverter module,
A voltage detecting module for detecting a voltage supplied to the welding electrode;
A current correction value calculation module for calculating a current correction value to be applied to the welding electrode from a voltage detected by the voltage detection module and a predetermined target power;
A control signal generation module for generating a switch control signal for driving the inverter module according to the calculated current correction value; And
And a controller for controlling the inverter module according to the generated switch control signal,
/ RTI >
Wherein the target power includes constant power having a constant value or variable power capable of being variable,
Spot welding system. The method according to claim 1,
The voltage detection module includes:
And a low-pass filter for low-pass filtering the detected voltage. The method according to claim 1,
In the spot welding system,
A current detection module for detecting a current provided to the welding electrode;
A power calculation module for calculating a current power provided to the welding electrode from the detected voltage and current; And
And a display module for displaying at least one of the calculated current power, the detected voltage and current, the resistance calculated from the detected voltage and current, and the amount of power of the current power. delete The method according to claim 1,
The power supply unit,
A first rectification module for rectifying an input AC power;
A capacitor module for converting AC power rectified by the first rectification module to DC power;
An inverter module including a plurality of switching elements for switching the DC power converted by the capacitor module according to the switch control signal;
A transformer module for stepping up or down the power source switched by the inverter module; And
And a second rectification module for rectifying the step-up or step-down power by the transformer module. A power control method of a spot welding system, comprising: a welding electrode; and a power supplier for providing a desired target power to the welding electrode by controlling an inverter module,
Detecting a voltage provided to the welding electrode;
Calculating a current correction value to be applied to the welding electrode from the detected voltage and a predetermined target power;
Generating a switch control signal for driving the inverter module according to the calculated current correction value; And
Controlling the inverter module according to the generated switch control signal, thereby providing the target electric power to the welding electrode
Lt; / RTI >
Wherein the target power includes constant power having a constant value or variable power capable of being variable,
A method of power control of a spot welding system. The method according to claim 6,
Wherein the step of detecting the voltage comprises:
And low-pass filtering the detected voltage. ≪ Desc / Clms Page number 21 > The method according to claim 6,
The power control method includes:
Detecting a current provided to the welding electrode;
Computing current power provided to the welding electrode from the detected voltage and current; And
Further comprising displaying at least one of the calculated current power, the detected voltage and current, the resistance calculated from the detected voltage and current, and the amount of power of the current power. delete The method according to claim 6,
The power supply unit,
A first rectification module for rectifying an input AC power;
A capacitor module for converting AC power rectified by the first rectification module to DC power;
An inverter module including a plurality of switching elements for switching the DC power converted by the capacitor module according to the switch control signal;
A transformer module for stepping up or down the power source switched by the inverter module; And
And a second rectification module for rectifying the step-up or step-down power by the transformer module.

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