JP2000033482A - Method for controlling controller for welding apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To sufficiently apply the capacity of a control device and to execute the control of the speed of a motor, torque developed with the motor and current for welding in a sufficient accuracy by changing sampling periods to the motor speed, the supplying current into the motor and the current for welding with a shifting mode of a gun arm with the motor and a welding mode for supplying the current to the gun arm. SOLUTION: In the shifting mode, since the welding work is not executed, the sampling of the current for welding is not executed. On the other hand, since the rotation of the motor is necessary to control at the high accuracy, to the motor speed and the current for operating the motor, the sufficient control accuracy is obtd. i.e., the sampling is executed in the short period. In the welding mode, the sampling of the current for welding is executed in the sampling period T/2 corresponding to the peak of the primary side welding current of AC current. The sampling periods of the current for operating the motor and the motor speed are set to T/2 and 3T/2, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a welding current supply device for supplying a welding current for performing welding to a workpiece to a gun arm, and a motor for moving the gun arm. The present invention relates to a control method of a control device for a welding device, which is suitable for being applied to a control device for controlling the welding.

[0002]

2. Description of the Related Art Conventionally, a DC resistance welding apparatus has been used as an apparatus for welding a workpiece. This DC resistance welding apparatus generally includes a pair of gun arms including a welding tip for sandwiching a workpiece, a driving device for driving the gun arm, and converting an AC current to a DC current to supply the DC current between the welding tips. And a transformer.

An electric motor can be used as the driving device. In this case, the control device for the motor and the control device for supplying the AC current to the transformer are connected to one CPU.
May be constituted by one DSP (digital signal processing device) having the following.

[0004] The DSP comprises a motor rotation speed (motor speed), a driving current supplied to the motor (motor driving current), and a current supplied between a transformer and a welding tip (primary and secondary welding). Current).

[0005] In this case, since the primary side welding current is an alternating current, the sampling cycle is set corresponding to the peak of the primary side welding current. Also, the secondary welding current is a DC current, and the sampling cycle of the secondary welding current is the same as the sampling cycle of the primary welding current because the sampling cycle can be set arbitrarily. It is said.

The sampling cycle of the motor driving current and the motor speed is determined based on the characteristics of the motor. Generally, the sampling cycle of the motor driving current is set to a shorter value than the sampling cycle of the welding current. The sampling period of the motor speed is set to a longer value than the sampling period of the motor driving current.

More specifically, as shown in FIG. 4, if the cycle of the alternating current supplied to the transformer is T (= 100 μs), the sampling cycle of the welding current is set to T / 2, The current sampling period is, for example,
Is set to T / 4, and the sampling period of the motor speed is
For example, it is set to 3T / 4.

[0008]

By the way, the above-mentioned D
In the SP, the sampling of the motor speed, the motor driving current, and the welding current must be constantly performed for each sampling cycle (3T / 4, T / 4, T / 2), so the sampling cycle is set short. Then, the DS
Due to the ability of P, there is a case where each of the sampling processes cannot be performed within a predetermined sampling period. For this reason, there is a problem that the sampling period cannot be set short, and the processing accuracy with respect to the motor speed and the like decreases. In order to avoid this, it is conceivable to employ a plurality of DSPs, but in this case, the cost is increased.

The present invention has been made in view of such problems, and can make full use of the capability of the control device, and furthermore, the rotational speed of the motor, the torque generated by the motor, and the welding current. It is an object of the present invention to provide a control method of a control device for a welding device, which enables the control of welding to be performed with sufficient accuracy.

[0010]

According to the present invention, there is provided a welding current supply device for supplying a welding current for performing welding to a workpiece to a gun arm, and a motor for driving the gun arm. In a control device that controls the welding device by one CPU, the motor is rotated in a movement mode in which the motor is rotated to move the gun arm, and a welding mode in which the welding current is supplied to the gun arm to perform a welding operation. The sampling cycle for at least one of the speed and the supply current to the motor is changed, and the sampling cycle for the welding current is changed (the invention according to claim 1).

Specifically, in the moving mode, sampling is not performed on the welding current, and the sampling period for at least one of the speed of the motor and the current supplied to the motor in the moving mode is set to the sampling period in the welding mode. It is set to be shorter than the sampling period (the invention according to claim 2).

In this case, since the welding current is not sampled in the moving mode, even when the sampling period for at least one of the motor speed and the current supplied to the motor is set short, the sampling can be reliably performed. it can. Further, in the welding mode, by setting the sampling cycle for at least one of the motor speed and the supply current to the motor longer than the sampling cycle in the movement mode, the motor speed and the supply current to the motor are set. Sampling and at least one of the welding current can be reliably performed.

Therefore, the capability of the control device can be fully utilized, and the motor and the welding current supply device can be controlled with sufficient accuracy.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a control device for a welding device to which a control method according to the present invention is applied will be described below with reference to FIGS. 1, 2, 3A and 3B.

First, the configuration of a welding device to which the control device according to the present embodiment is applied will be briefly described.

As shown in FIG. 1, a welding apparatus (DC resistance welding apparatus) 10 has a pair of gun arms 12a and 12b for performing welding on works (workpieces) W1 and W2. Welding tips 14a, 14b are provided at opposite ends of 12a, 12b. The gun arms 12a and 12b are connected by a joint member 16, and the gun arms 12a and 12b are connected to each other.
Under the driving action of an actuator 18 attached to the rear end side of 2b, the tip portions are displaced in a direction approaching or moving away from each other.

The driving source of the actuator 18 is a motor (AC servo motor: M) 20.
Is connected to the control device 100 via cables 24a to 24c (when not particularly required to be separately described, is referred to as a cable 24), and is supplied with an alternating current (motor driving current) from the control device 100. Thus, the motor rotates at a predetermined rotation speed (motor speed) and output (torque).

The gun arms 12a and 12b are fixed to a transformer with rectifier (current supply device for welding: TR) 26 via one of the gun arms 12b. The gun arms 12a, 12b are connected to a transformer 26 via cables 126a, 126b, and welding work is performed on the works W1, W2 by a welding current supplied from the transformer 26 to between the welding tips 14a, 14b. . The transformer 26 is fixed to a robot arm (not shown). By displacing the robot arm, the gun arms 12a and 12b
1. It is moved to the desired welding site of W2.

Next, a control device according to the present embodiment will be described with reference to FIGS. 2, 3A and 3B.

As shown in FIG. 2, a control unit (DSP) 1
00 is a central processing unit having a calculation control function.
U102, and a bus 104
(Read only memory) 106 in which a control program is stored, a RAM (random access memory) 108 as a temporarily used storage means, and a DPRAM (dual port RA) functioning as an interface.
M) 110 is connected. An upper controller 112 is connected to the DPRAM 110, and a CP is sent from the controller 112 via the DPRAM 110.
Command data for operating U102 is supplied.

A bus 104 outputs an AC current signal having a pulse train based on a command from the CPU 102.
WM (pulse width modulation) generators 114 and 116 are connected, and these PWM generators 114 and 116 are connected to an inverter 118 that outputs an AC current based on an AC current signal from the PWM generators 114 and 116.
120 are respectively connected.

One inverter 118 is configured to output a two-phase AC current (primary welding current), and the primary welding current is supplied to the cables 122a and 122a.
It is supplied to the transformer 26 via 2b. Transformer 26
Converts the AC current into a DC current (secondary welding current) and supplies it to the gun arms 12a and 12b via the cables 126a and 126b. The other inverter 120 is configured to output a three-phase AC current (motor driving current).
4 to the motor 20.

The bus 104 is connected to an A / D converter 128 for U-phase and an A / D converter 130 for V-phase for converting an analog signal into digital data.
The / D converters 128 and 130 are connected to a multiplexer 132. The multiplexer 132 is connected to the cable 12
2a, a current sensor 134 and a cable 126a
Current sensor 136 and cables 24a,
4b is connected to the current sensors 138a and 138b provided by wires, and a detection value Iw1 of the primary-side welding current is output from the current sensor 134 to the current sensor 13b.
6, the detection value Iw2 of the secondary welding current is supplied, and the current sensors 138a, 138b supply the detection values Ima, Imb of the motor driving current. this house,
The detected value Iw1 of the primary welding current and the detected value Ima of the motor driving current are output from the multiplexer 132 to the A / D converter 128, and the detected value Iw of the secondary welding current is output.
2 and the detected value Imb of the motor driving current are output from the multiplexer 132 to the A / D converter 130.

Further, the bus 104 has an interface 1
40 are connected. The interface 140 is connected to a pulse generator 142 provided on the motor 20 by wiring, and a detection pulse pk output every time the motor 20 rotates a predetermined angle is supplied from the pulse generator 142. The detection pulse pk is converted into a voltage signal indicating the rotation speed (motor speed) V of the motor 20 by an F / V converter (not shown) and output to the bus 104.

Next, the control device 100 according to the present embodiment
3 will be described in detail with reference to timing charts shown in FIGS. 3A and 3B.

The CPU 102 operates according to a control program supplied from the ROM 106. In this case, CP
U102 receives command data from the host controller 112, the multiplexer 132 and the A / D converters 128, 1
30, the detected values Ima and Imb of the motor driving current supplied via the interface 140, the detected value Iw1 of the primary welding current, and the detected value I of the secondary welding current
Based on w2 and the detection pulse pk (motor speed V), the current value and frequency of the alternating current supplied to the transformer 26 and the motor 20 are determined, and the PWM generator 114,
116.

Here, the processing operation in the CPU 102 is performed at the timing (sampling cycle) shown in the timing charts of FIGS. 3A and 3B. That is, input / output switching between the multiplexer 132 and the interface 140 is performed based on the timing.
In this case, the sampling cycle is changed according to the operation mode of the welding device 10 (moving mode and welding mode described later).

As the motor 20 rotates, the gun arm 12
FIG. 3A is a timing chart showing a specific example of the sampling period in the mode in which the a and 12b move (moving mode), and the sampling period in the mode (welding mode) for supplying a welding current between the gun arms 12a and 12b. A specific example is shown in the timing chart of FIG. 3B.

As shown in FIG. 3A, since no welding operation is performed in the moving mode, the sampling of the welding current is not performed. On the other hand, since the rotation of the motor 20 needs to be controlled with high accuracy, the motor speed and the motor driving current are sampled at a sampling period (ie, a short sampling period) at which sufficient control accuracy is obtained. . Here, the cycle of the primary side welding current is T (= 10
0 μs), the sampling period of the motor driving current is T / 4, and the sampling period of the motor speed is 3T / 4.

As described above, since the welding current is not sampled in the moving mode, even when the motor speed and the sampling period of the motor driving current are set short,
Sampling processing for the motor speed and the motor driving current in the CPU 102 is reliably performed.

As shown in FIG. 3B, in the welding mode, the welding current is sampled at a sampling cycle (T / 2) corresponding to the peak of the primary side welding current, which is an alternating current. At this time, the pressing force applied to press the works W1 and W2 to the motor 20 is applied to the gun arm 12.
Since it is necessary to perform torque control for generating torques at the a and 12b, the sampling period of the motor driving current is set to a sufficient sampling period (T / T) for performing the torque control.
Set to 2). The motor speed sampling period is
For example, 3T / 2 capable of detecting an operation abnormality
Is set to

As described above, the sampling period of the motor speed and the motor driving current in the welding mode is set longer than the sampling period of the motor speed and the motor driving current in the moving mode.
No. 02 can reliably perform sampling processing for all of the welding current, the motor speed, and the motor driving current.

In this embodiment, the gun arm 12
The motors 20 for driving the motors a and 12b are controlled. In addition, a motor constituting a robot arm (not shown) for moving the gun arms 12a and 12b and the transformer 26 is controlled and welding is performed. Not only the motors constituting the device, but also a plurality of motors whose required control accuracy changes during operation can be set as control targets. In this case, the sampling period is set to a desired value based on the required control accuracy, as in the present embodiment.

In the present embodiment, the welding current is selected as a sampling target, and when either one of the motor driving current and the motor speed is selected, the same as the sampling period is applied to these. Sampling can be performed periodically. Of course, CPU1
The sampling cycle for either the motor driving current or the motor speed selected here may be changed in accordance with the capacity of the motor No. 02.

As described above, in the present embodiment, the welding current is not sampled in the moving mode. Further, the sampling cycle of the motor driving current and the motor speed in the moving mode is set to be shorter than the sampling cycle of the motor driving current and the motor speed in the welding mode.

In this case, since the welding current is not sampled in the moving mode, even when the sampling period of the motor speed and the motor driving current is set short, the sampling for the motor speed and the motor driving current is reliably performed. be able to. Further, in the welding mode, by setting the sampling period of the motor speed and the motor driving current longer than the sampling period of the motor speed and the motor driving current in the moving mode, the welding current, the motor speed and the motor Sampling for all of the drive currents can be reliably performed.

Therefore, the ability of the control device 100 can be fully utilized, and the rotational speed of the motor 20 can be improved.
The torque generated by the motor 20 and the welding current can be controlled with sufficient accuracy.

It should be noted that the present invention is not limited to the above-described embodiment, but can adopt various configurations without departing from the gist of the present invention.

[0039]

As described above, according to the present invention, a welding current supply device for supplying a welding current for performing welding to a work to a gun arm, and a motor for moving the gun arm are provided. In a control device that controls a welding device having a single CPU, the capability of the control device can be fully utilized, and the control of the rotation speed of the motor, the torque generated by the motor, and the welding current can be performed. It can be performed with sufficient accuracy.

[Brief description of the drawings]

FIG. 1 is a plan view showing a schematic configuration of a welding apparatus to which an embodiment of the present invention is applied.

FIG. 2 is a block diagram illustrating a schematic configuration of a control device.

FIG. 3 shows a timing of processing in the control device, FIG. 3A is a timing chart showing a sampling cycle in a moving mode, and FIG. 3B is a timing chart showing a sampling cycle in a welding mode.

FIG. 4 is a timing chart showing the timing of processing in a control device according to the related art.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Welding device 12a, 12b ... Gun arm 20 ... Motor 26 ... Transformer 100 ... Control device 102 ... CPU 104 ... Bus 106 ... ROM 108 ... RAM 110 ... DPRAM 114, 116 ... PWM generators 118, 120 ... Inverters 128, 130 ... A
/ D converter 132: multiplexers 134, 136, 138a, 138b: current sensor 140: interface 142: pulse generator

Claims (2)

[Claims] A single CPU controls a welding device having a welding current supply device for supplying a welding current for performing welding to a workpiece to a gun arm, and a motor for driving the gun arm. A control method applied to a control device that performs a welding operation by rotating the motor and moving the gun arm; and a welding mode in which the welding current is supplied to the gun arm to perform a welding operation. And changing the sampling period for at least one of the speed and the supply current to the motor and changing the sampling period for the welding current. 2. The method according to claim 1, wherein in the moving mode, sampling is not performed on the welding current, and a sampling period for at least one of the speed of the motor and the current supplied to the motor in the moving mode is set as: A control method for a control device for a welding device, wherein the sampling period in the welding mode is set shorter than the sampling period.