JP3692233B2 - Drive control device and drive control method for welding gun arm - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a drive control device and a drive control method for a welding gun arm for controlling the drive of a gun arm constituting a welding device.
[0002]
[Prior art]
Generally, a resistance welding machine that applies a voltage (current) to a workpiece and welds the workpiece has a pair of gun arms that sandwich and pressurize a portion where the workpiece is welded. The gun arm is provided with a driving device, and is displaced in a direction approaching or separating from each other under the biasing action of the driving device. Conventionally, a fluid pressure type cylinder has been used as the driving device.
[0003]
[Problems to be solved by the invention]
By the way, as the drive device, an electric motor can be used instead of the fluid pressure type cylinder.
[0004]
The present invention relates to a drive control device and a drive control method for a welding gun arm configured using this electric motor, and after the gun arm is displaced in the direction approaching the work and collides with the work, the work is stopped and the work is added. It is an object of the present invention to provide a drive control device and a drive control method for a welding gun arm capable of suitably controlling the pressing operation.
[0005]
[Means for Solving the Problems]
In the welding gun arm drive control apparatus according to the present invention, the motor for driving the welding gun arm is the current value or the second calculation obtained by the first calculation means from the deviation between the set speed of the motor and the actual rotation speed. The control unit controls the current value obtained from the set speed, the rotation speed, and the predetermined set current value based on a predetermined calculation formula.
[0006]
In this case, since the motor can be driven in different operation modes, for example, when the gun arm is moved at a high speed, the motor is supplied with the current value from the first calculation means, so that the motor is set at a set speed. The gun arm can be rotated to reduce the movement time of the gun arm, and when the gun arm collides with a workpiece, the current value from the second calculation means is supplied to the motor. Thus, the current value can be set so that the impact generated at the time of the collision is reduced.
[0007]
  Further, the current value from the first calculation means and the current value from the second calculation means are switched by the switching means.The WhereThe switching operation in the switching means may be performed based on a signal output from the timing detection means at a predetermined timing based on the set speed and the rotation speed.Yes.In this case, the operation mode of the motor can be easily switched corresponding to the operation schedule of the motor.
[0008]
  Further, the calculation for obtaining the current value in the second calculating means is performed when the current value changes in an inclined manner with respect to the change in the rotation speed of the motor and the rotation speed is the same as the set speed of the motor. When the current value is 0 and the rotation speed is 0, the current value may be set based on a calculation formula configured to be the set current value.Yes.
[0009]
In this case, since the torque generated in the motor increases from 0 as the motor decelerates, for example, when the gun arm collides with the workpiece, a large torque is instantaneously generated in the motor. It is avoided that a large impact is applied to the gun arm or the workpiece.
[0010]
  Further, the calculation of the current value in the second calculation means is expressed by the following equation:
    I = (1−V / V0) × Ic
You can do it based onYes.In this case, the current value can be obtained by a simple calculation formula, and the configuration of the second calculation means can be simplified and the calculation time can be shortened.
[0011]
  next,BookIn the present invention, a series of operations of stopping and pressurizing the workpiece after the gun arm approaches and collides with the workpiece, an approach stage in which the gun arm approaches the workpiece, and the gun arm collides with the workpiece and stops. The operation mode of the motor is changed at the collision stop stage.
[0012]
In this case, in the approaching stage, for example, an operation mode capable of moving the gun arm at high speed is selected, and in the collision stopping stage, for example, the impact generated when the gun arm collides with the workpiece is reduced, and By selecting an operation mode capable of reducing the time for shifting from the collision to pressurization, it is possible to reduce the welding time and to prevent the welding quality from being deteriorated by the collision.
[0013]
  Further, a current value to be supplied to the motor is obtained based on a deviation between the set rotational speed of the motor and the actual rotational speed in the approaching stage, and the set rotational speed of the motor and the actual rotational speed in the collision stopping stage. It may be determined from a speed and a predetermined set current value based on a predetermined calculation formula.Yes.
[0014]
In this case, in the approaching stage, high responsiveness to the set speed of the motor rotation speed can be obtained, and in the collision stopping stage, the gun arm pressurizes the work from the collision with the work. By arbitrarily setting the torque to be generated in the motor based on the calculation formula, the welding time can be shortened and the welding quality can be improved.
[0015]
  Further, the calculation of the current value performed in the collision stop stage is performed when the current value supplied to the motor changes in an inclined manner with respect to the change in the rotation speed of the motor, and the rotation speed is the same as the set rotation speed. When the current value becomes 0 and the motor stops and the rotation speed becomes 0, the current value may be set based on a calculation formula configured to be the set current value.Yes.In this case, by setting the torque generated in the motor as the motor decelerates to increase, for example, from 0, the motor momentarily increases when the gun arm collides with the workpiece. And it is avoided that a large impact is applied to the gun arm or the workpiece.
[0016]
  In addition, the calculation of the current value performed in the collision stop stage, the following formula,
    I = (1−V / V0) × Ic
You can do it based onYes.In this case, the current value can be obtained by simple calculation, and the means for calculating the current value can be simplified and the calculation time can be shortened.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a welding gun arm drive control device and drive control method according to the present invention (hereinafter simply referred to as a control device according to embodiments) will be described below with reference to FIGS.
[0021]
Before describing the control device according to the present embodiment, the configuration of the welding device will be briefly described.
[0022]
As shown in FIG. 1, a welding apparatus 10 to which a control device according to the present embodiment is applied includes a first gun arm 12 and a second gun arm 14 which are a pair of gun arms for performing welding on workpieces W1 and W2. Welding tips 16a and 16b are provided at the tip portions of the first gun arm 12 and the second gun arm 14 facing each other.
[0023]
The first gun arm 12 is connected to a rotating shaft of a motor (AC servo motor) 20 fixed to a hollow cylindrical base 18 via a bearing member (not shown) provided on the first gun arm 12. And the inside of the base body 18 is displaced so as to freely advance and retract along the axial direction of the base body 18 under the driving action of the motor 20. The second gun arm 14 is fixed to the base 18. The first gun arm 12 and the second gun arm 14 are connected to a power supply device (not shown) for applying a welding voltage (current) between the welding tips 16a and 16b.
[0024]
The motor 20 is wired to a later-described servo amplifier 60 via cables 24a to 24c (in the case where it is not necessary to distinguish between the motors 20), and is connected to a servo amplifier 60 to be described later. And driven by output (torque). The rotation direction of the motor 20 is positive when the first gun arm 12 is moved forward and negative when the first gun arm 12 is moved backward.
[0025]
Next, the control device according to the present embodiment will be described.
[0026]
As shown in FIG. 1, the control device 100 according to the present embodiment includes a main controller 42 that controls the operation of the welding device 10 and the entire control device 100, speed data Dv0 and limit data supplied from the main controller 42. Based on the data Di and the actual speed data Dv obtained by the detector 44 provided in the motor 20 and the synchronization signal Sd, the current value and frequency of the alternating current to be supplied to the motor 20 are obtained, and the current value command signal Sic. , Sid output speed control unit 50, and current value command signals Sic, Sid from speed control unit 50 are detected current value signals Sii supplied from current sensors 52a, 52b provided in cables 24a, 24b, A current control unit 54 that performs control based on Sij and outputs the current value command signals Sie and Sif; A PWM circuit 56 that modulates the pulse width based on the current value command signals Sie and Sif from the control unit 54 and outputs it as an alternating current signal having a pulse train, and a three-phase alternating current based on the alternating current signal from the PWM circuit 56 A servo amplifier 60 that supplies (current value I) to the motor 20, and a timing detection unit (timing detection) that detects a predetermined timing based on the speed data Dv0 and the actual speed data Dv and outputs a timing signal St at this timing. Means) 82.
[0027]
In particular, the speed control unit 50 obtains the current value of the alternating current to be supplied to the motor 20 based on the speed data Dv0, limit data Di, and actual speed data Dv, and outputs the current value as a current value command signal Sia or Sih. A calculation means 102; a limit means 64 for limiting the upper limit of the current value command signal Sia or Sih from the current value calculation means 102 based on the limit data Di and outputting it as a current value command signal Sib; and the limit means 64 Distribution means 66 for outputting the current value command signal Sib from the output as pulsed current value command signals Sic and Sid at a timing based on the synchronization signal Sd.
[0028]
As shown in FIG. 2, the current value calculation means 102 calculates a speed deviation based on the speed data Dv0 and the actual speed data Dv, and outputs it as speed deviation data Dσ (first calculation). Means) 68, deviation current value calculation means (first calculation means) 70 for calculating a current value based on the speed deviation data Dσ from the speed deviation calculation means 68 and outputting it as a current value command signal Sia, and the speed A coefficient calculation means (second calculation means) 104 for calculating a coefficient based on a predetermined calculation formula from the data Dv0 and the actual speed data Dv and outputting it as coefficient data Dk, the coefficient data Dk from the coefficient calculation means 104 and the main A coefficient for obtaining the current value of the alternating current to be supplied to the motor 20 based on the limit data Di from the controller 42 and outputting it as the current value command signal Sih Based on the current value calculation means (second calculation means) 106 and the timing signal St from the timing detector 82, the current value command signal Sia from the deviation current value calculation means 70 and the coefficient current value calculation means 106 And a selector (switching means) 108 for switching the current value command signal Sih to output to the limit means 64.
[0029]
The detector 44 shown in FIG. 1 includes a speed sensor that detects the rotation frequency of the motor 20 and outputs it as a rotation frequency signal, and a magnetic pole sensor that detects the position of the magnetic pole of the motor 20 and outputs it as a synchronization signal Sd. Has been. Specifically, it is configured by an optical encoder, a magnetic encoder or the like provided with the speed sensor and the magnetic pole sensor. The rotation frequency signal from the detector 44 is converted into a voltage signal by the F / V conversion circuit 72, and then converted into digital data by the A / D conversion circuit 74, so that the actual speed data Dv (rotation speed) is obtained. V). Further, the frequency of the three-phase alternating current supplied from the servo amplifier 60 to the motor 20 is determined by the synchronization signal Sd.
[0030]
The servo amplifier 60 temporarily converts a three-phase AC current supplied from a power source (not shown) connected through terminals 58a to 58c (hereinafter referred to as a terminal 58) into a DC current, and then the AC from the PWM circuit 56. The motor 20 is configured to be reconverted into a three-phase alternating current based on the current signal.
[0031]
The speed data Dv0 is stored in a storage means (not shown) of the main controller 42 as a speed look-up table for setting a schedule (speed schedule) for the rotation speed V of the motor 20. The speed data Dv0 is read from the speed lookup table every predetermined time, and is output from the main controller 42 as a set rotational speed for setting the rotational speed of each time of the motor 20. The speed lookup table is stored as a plurality of data groups in the storage means of the main controller 42, and a desired one is selected from them.
[0032]
The limit data Di is stored in the storage means of the main controller 42 as a limit lookup table for setting a limit value schedule (limit schedule) for limiting the upper limit of the current value I of the alternating current to be supplied to the motor 20. Has been. The limit data Di is read from the limit lookup table every predetermined time and output from the main controller 42 as a set limit value (set current value) for setting a limit value for each time of the current value I. Is done. The limit look-up table is stored as a plurality of data groups in the storage means of the main controller 42 as with the speed data Dv0, and a desired one is selected from them.
[0033]
The operation schedule of the motor 20 is determined by the speed schedule and the limit schedule.
[0034]
Next, the processing operation of the control device 100 according to the present embodiment will be described.
[0035]
A set rotational speed is supplied as speed data Dv0 from the main controller 42 to the speed deviation calculating means 68 and coefficient calculating means 104 constituting the current value calculating means 102, and the coefficient current value calculating means 106 of the current value calculating means 102 and A set limit value is supplied as limit data Di to the limit means 64 (see FIGS. 1 and 2). Further, the rotational speed V of the motor 20 is supplied as the actual speed data Dv from the detector 44 to the speed deviation calculating means 68 and the coefficient calculating means 104 via the F / V conversion circuit 72 and the A / D conversion circuit 74.
[0036]
The timing detector 82 detects a predetermined timing based on the speed data Dv0 (set rotational speed) and the actual speed data Dv, and outputs a timing signal St to the main controller 42 and the selector 108 at this timing.
[0037]
The speed deviation calculating means 68 calculates a speed deviation based on the speed data Dv0 and the actual speed data Dv, and outputs it as speed deviation data Dσ. In this case, the value of the speed deviation data Dσ becomes a negative value when the value of the actual speed data Dv (the rotational speed V of the motor 20) exceeds the set rotational speed, and the rotational speed V becomes the set rotational speed. When the value is below, it becomes a positive value.
[0038]
The deviation current value calculation means 70 calculates a current value based on the speed deviation data Dσ from the speed deviation calculation means 68 and outputs it as a current value command signal Sia. In this case, the sign of the current value command signal Sia depends on the sign of the speed deviation data Dσ.
[0039]
On the other hand, the coefficient calculation means 104 calculates a coefficient based on a predetermined calculation formula from the speed data Dv0 and the actual speed data Dv, and outputs it as coefficient data Dk. Then, the coefficient current value calculating means 106 obtains the current value of the alternating current to be supplied to the motor 20 based on the coefficient data Dk from the coefficient calculating means 104 and the limit data Di from the main controller 42, and the current value Output as command signal Sih.
[0040]
The selector 108 switches between the current value command signal Sia from the deviation current value calculation means 70 and the current value command signal Sih from the coefficient current value calculation means 106 based on the timing signal St from the timing detection unit 82. To the limit means 64.
[0041]
The limit means 64 limits the upper limit of the current value command signal Sia or Sih from the selector 108 based on the limit data Di and outputs it as a current value command signal Sib. In this case, the upper limit of the current value command signal Sia or Sih is limited as an absolute value, and does not depend on the sign of the value.
[0042]
The distribution unit 66 outputs the current value command signal Sib from the limit unit 64 as pulsed current value command signals Sic and Sid at a timing based on the synchronization signal Sd supplied from the detector 44.
[0043]
The current control unit 54 controls the current value command signals Sic and Sid from the distribution means 66 based on the detected current value signals Sii and Sij supplied from the current sensors 52a and 52b, and the current value command signals Sie and Sif. Output as.
[0044]
The PWM circuit 56 modulates the pulse width based on the current value command signals Sie and Sif from the current control unit 54 and outputs it as an alternating current signal having a pulse train. In this case, the frequency of the alternating current signal depends on the timing (pulse period) of the current value command signals Sic and Sid output from the distribution means 66.
[0045]
The servo amplifier 60 once converts a three-phase alternating current supplied from a power source (not shown) connected via a terminal 58 into a direct current, and then reconverts it into a three-phase alternating current based on the alternating current signal from the PWM circuit 56. This is converted and supplied to the motor 20. The alternating current is in a rank phase with respect to the rotating magnetic field of the motor 20 when the value of the current value command signal Sia is positive, and is in the opposite phase when negative.
[0046]
The motor 20 rotates by generating a torque depending on the current value I of the alternating current supplied from the servo amplifier 60. In this case, the period of the alternating current is modulated in synchronization with the rotation of the motor 20. The motor 20 is accelerated or decelerated by increasing or decreasing the current value I and rotating the phase forward and backward.
[0047]
The first gun arm 12 advances and retreats with respect to the base body 18 by the rotation of the motor 20. The position at which the welding tip 16a provided at the tip of the first gun arm 12 contacts the workpiece W1 is referred to as the welding position of the first gun arm 12.
[0048]
Thus, in the control device 100 according to the present embodiment, the rotational speed V of the motor 20 that drives the first gun arm 12 can be controlled based on a predetermined speed schedule. It is possible to arbitrarily set the advance / retreat speed.
[0049]
Further, limit data Di (set limit value) to be supplied from the main controller 42 to the limit means 64 is output from the timing detector 82 at a predetermined timing based on the speed data Dv0 (set rotation speed) and the actual speed data Dv. Therefore, the timing for changing the set limit value can be set according to the speed schedule.
[0050]
In addition, according to the timing signal St supplied from the timing detection unit 82 to the selector 108, the signal output from the selector 108 (that is, the current value calculation unit 102) is output by the speed deviation calculation unit 68 and the deviation current value calculation unit 70. The obtained current value command signal Sia can be changed to the current value command signal Sih obtained by the coefficient calculation means 104 and the coefficient current value calculation means 106. Therefore, the motor 20 can be driven in different operation modes during one welding operation. As a result, the operation mode of the motor 20 is changed, for example, when the first gun arm 12 is displaced to the vicinity of the welding position and immediately before the first gun arm 12 collides with the workpiece W1. It is possible to perform the displacement in a short time and to buffer an impact when the first gun arm 12 collides with the workpiece W1.
[0051]
Note that the current value calculation means 102 may be constituted by a plurality of coefficient calculation means 104 and coefficient current value calculation means 106. In this case, the motor 20 can be driven in a plurality of operation modes during one welding operation.
[0052]
Further, by supplying the timing signal St from the timing detection unit 82 to the coefficient calculation unit 104 and the coefficient current value calculation unit 106, the calculation formulas set in the coefficient calculation unit 104 and the coefficient current value calculation unit 106 are changed. It is also possible to configure so as to. Also in this case, the motor 20 can be driven in a plurality of operation modes during one welding operation.
[0053]
Next, an example of the control device 100 according to the present embodiment will be described.
[0054]
In this embodiment, the coefficient calculation by the coefficient calculation means 104 is performed based on the following equation.
[0055]
k = 1-V / V0 (1)
Here, k is a coefficient, V is the rotation speed of the motor 20 supplied as actual speed data Dv, and V0 is the set rotation speed (high speed Va or low speed Vb) of the motor 20 supplied as speed data Dv0. Respectively.
[0056]
On the other hand, the calculation of the current value in the coefficient current value calculation means 106 is performed based on the following equation.
[0057]
I = k × Ic (2)
Here, I is a current value output as the current value command signal Sih (the same value as the current value of the alternating current supplied to the motor 20), k is the coefficient, and Ic is a set limit supplied as limit data Di. Each of the values {set current value (high limit value Ia or low limit value Ib)}.
[0058]
Further, as shown in FIGS. 3A to 3C, the speed schedule (shown by a dotted line in FIG. 3A) is such that the set rotational speed becomes the high speed Va during the period from the time point a to c, and becomes the low speed Vb after the time point c. Is set to On the other hand, the limit schedule (indicated by a dotted line in FIG. 3B) is set such that the set limit value becomes the high limit value Ia during the period from the time point a to d and becomes the low limit value Ib after the time point d. The set rotational speed and the set limit value are assumed to be 0 in the initial state (before time point a). FIG. 3C shows the characteristics of the pressure applied to the first gun arm 12.
[0059]
Further, when the timing detector 82 detects that the rotational speed V of the motor 20 has reached the low speed Vb after the set rotational speed has been changed from the high speed Va to the low speed Vb, the motor 20 Is set to output a timing signal St when a decrease in the rotational speed V of the motor 20 is detected during driving and when a stop of the motor 20 is detected while the motor 20 is also driven at the low speed Vb. ing.
[0060]
Further, it is assumed that the current value command signal Sia supplied from the deviation current value calculation means 70 is selectively output from the selector 108 during the period from the time point a to d.
[0061]
First, at a time point a, a set rotational speed (high speed Va) is supplied as speed data Dv0 from the main controller 42 to the speed deviation calculation means 68 constituting the current value calculation means 102, and to the limit means 64. Thus, the set limit value (high limit value Ia) is supplied as limit data Di (see FIGS. 1 and 2). Along with this, the motor 20 starts.
[0062]
That is, since the rotational speed V of the motor 20 is 0 at this time point a, the speed deviation calculating means 68 obtains a positive value based on the deviation between the rotational speed V and the set rotational speed (high-speed speed Va). Speed deviation data Dσ is output. With the supply of the speed deviation data Dσ, the deviation current value calculation means 70 starts outputting a positive current value command signal Sia based on the speed deviation data Dσ to start the motor 20.
[0063]
Until the rotation speed V of the motor 20 reaches the high speed Va, the value of the speed deviation data Dσ output from the speed deviation calculation means 68 is positive based on the deviation between the rotation speed V of the motor 20 and the high speed Va. Therefore, the value of the current value command signal Sia output from the deviation current value calculation means 70 also becomes a positive value based on the deviation, and the motor 20 continues to accelerate (acceleration during the period from time point a to b). region). In this case, when the current value command signal Sia exceeds the high limit value Ia, the limit means 64 outputs a current value command signal Sib in which the upper limit of the current value command signal Sia is limited by the high limit value Ia.
[0064]
When the rotational speed V of the motor 20 reaches the high speed Va, the speed deviation calculated by the speed deviation calculating means 68 becomes substantially zero, so the value of the current value command signal Sia output from the deviation current value calculating means 70 is Then, the speed of the motor 20 is reduced to a value (approximately 0) necessary for maintaining the high speed Va (time b). Then, the motor 20 is driven at a constant speed Va at a high speed Va until a time point c (a period of time points b to c during a high speed drive region).
[0065]
At the time point c, the set rotational speed supplied from the main controller 42 to the speed deviation calculation means 68 as the speed data Dv0 is changed from the high speed Va to the low speed Vb. At this time, since the rotational speed V of the motor 20 exceeds the low speed Vb, the speed deviation calculation means 68 gives negative speed deviation data based on the deviation between the rotational speed V and the low speed Vb. Dσ is output. The deviation current value calculation means 70 outputs a negative current value command signal Sia based on the speed deviation data Dσ to decelerate the motor 20. Along with this, the motor 20 starts to decelerate.
[0066]
Until the rotational speed V of the motor 20 reaches the low speed Vb, the speed deviation data Dσ output from the speed deviation calculating means 68 is a negative value based on the deviation between the rotational speed V and the low speed Vb. The current value command signal Sia output from the deviation current value calculation means 70 also becomes a negative value based on the deviation, and the motor 20 continues to decelerate (period of time point cd).
[0067]
When the rotational speed V of the motor 20 reaches the low speed Vb, the speed deviation calculated by the speed deviation calculating means 68 becomes almost zero. Therefore, the value of the current value command signal Sia sets the speed of the motor 20 to the low speed Vb. To a value (approximately 0) necessary to maintain the value (decrease when viewed as an absolute value) (time point d). At this time, when the timing detector 82 detects that the rotational speed V of the motor 20 has reached the low speed Vb, it outputs a timing signal St to the main controller 42 and the selector 108.
[0068]
Based on this timing signal St, the main controller 42 changes the set limit value to be supplied as the limit data Di to the limit means 64 from the high limit value Ia to the low limit value Ib (see time point d in FIGS. 3A and 3B). ).
[0069]
On the other hand, the selector 108 is supplied from the coefficient current value calculation means 106 instead of the current value command signal Sia supplied from the deviation current value calculation means 70 based on the timing signal St from the timing detection unit 82. The current value command signal Sih is output. Thereby, the operation mode of the motor 20 is changed.
[0070]
At this time, the coefficient calculation means 104 performs a calculation based on the equation (1) from the speed data Dv0 and the actual speed data Dv, obtains the coefficient k, and outputs it as the coefficient data Dk. Actually, the set rotational speed V0 supplied to the coefficient calculating means 104 as the speed data Dv0 is the low speed Vb, and the rotational speed of the motor 20 supplied to the coefficient calculating means 104 as the actual speed data Dv. Since V has reached the low speed Vb, V / V0 = 1, and the coefficient k obtained at this point d is almost zero.
[0071]
The coefficient current value calculation means 106 performs a calculation based on the equation (2) on the basis of the coefficient data Dk from the coefficient calculation means 104 and the limit data Di (low limit value Ib) from the main controller 42 to obtain a current. A value I is obtained and output as a current value command signal Sih. Actually, since the coefficient k supplied as the coefficient data Dk is almost zero, the current value I obtained here is also almost zero.
[0072]
As a result, no torque is generated in the motor 20, and the motor 20 is driven at a constant speed at the low speed Vb (the period from the time point d to e). However, when a fluctuation occurs in the rotational speed V of the motor 20, a current value I for canceling the fluctuation is obtained based on the expressions (1) and (2) and supplied to the motor 20.
[0073]
When the tip of the first gun arm 12 collides with the workpiece W1, the path of the first gun arm 12 is blocked and its forward speed decreases, and accordingly, the rotational speed V of the motor 20 also decreases (time point e). . In this case, it is assumed that the welding tip 16b at the tip of the second gun arm 14 is in contact with the other workpiece W2. At this time, since the rotational speed V of the motor 20 in the formula (1) is smaller than the set rotational speed V0 (low speed Vb), V / V0 <1, and the coefficient calculation means 104 is based on the formula (1). The coefficient k obtained in this way is a positive value.
[0074]
The current value I obtained by the coefficient current value calculation means 106 based on the equation (2) is also a positive value because the coefficient k supplied to the coefficient current value calculation means 106 as the coefficient data Dk is a positive value. It becomes. Therefore, an alternating current having a positive current value is supplied to the motor 20, and torque is generated in the motor 20.
[0075]
As the rotational speed V of the motor 20 decreases, the value of V / V0 in the equation (1) decreases, so the value of the coefficient k obtained by the coefficient calculation means 104 increases. In response to this, the current value I obtained from the coefficient current value calculation means 106 based on the equation (2) gradually increases, and the torque generated in the motor 20 based on this current value I also gradually increases (time point). (period of e to i, collision area).
[0076]
When the motor 20 stops, the rotational speed V of the motor 20 in the equation (1) becomes almost zero, so V / V0 = 0, and the coefficient k obtained by the coefficient calculation means 104 based on the equation (1) is almost the same. 1 Therefore, the current value I obtained by the coefficient current value calculation means 106 based on the equation (2) is almost the same value as the low limit value Ib. Accordingly, torque based on the low limit value Ib is generated in the motor 20 (time point i).
[0077]
As long as the motor 20 is stopped, the motor 20 generates a substantially constant torque based on the low limit value Ib. Accordingly, the first gun arm 12 and the second gun arm 14 pressurize the workpieces W1 and W2 by a substantially constant pressure generated between the first gun arm 12 and the second gun arm 14 in accordance with this torque (after the time point i, Pressure area).
[0078]
The timing signal St is supplied from the timing detector 82 to the selector 108 at the time point i, and the signal output from the selector 108 is changed from the current value command signal Sih to the current value command signal Sia to change the operation mode of the motor 20. It may be changed again.
[0079]
Thus, in the present embodiment, the process performed by the current value calculation unit 102 based on the timing signal St output from the timing detection unit 82 to the selector 108 at the time point d is the rotational speed V of the motor 20. Current value command signal Sia based on the formula (1) and formula (2) from the rotation speed V, the set rotation speed, and the set limit value. It is changed to the process to ask for.
[0080]
The equations (1) and (2) are set so that the current value command signal Sih increases in inverse proportion to the decrease in the rotation speed V as the rotation speed V of the motor 20 decreases. When the first gun arm 12 collides with the workpiece W1 and the motor 20 decelerates, a large torque is instantaneously generated in the motor 20, and the first gun arm 12 is elastically deformed to cause vibration. It can be avoided.
[0081]
Therefore, by calculating the current value of the current to be supplied to the motor 20 based on such a simple calculation formula, the collision area (period ei in FIG. 3A to FIG. 3C) is shortened, and the welding time. Loss is avoided. Further, the configuration of the coefficient calculation means 104 and the coefficient current value calculation means 106 can be simplified.
[0082]
Comparative example
Next, in order to clarify the characteristics of the present invention, a comparative example for the present embodiment (example) will be described.
[0083]
First, a first comparative example will be described with reference to FIGS. 4 to 7C.
[0084]
As illustrated in FIG. 4, the control device 40 according to the first comparative example is configured not to include the timing detection unit 82 with respect to the control device 100 according to the present embodiment illustrated in FIG. 1. Further, the limit data Di is not supplied to the current value calculation means 62.
[0085]
Further, as shown in FIG. 5, the current value calculating means 62 is configured not to include the coefficient calculating means 104, the coefficient current value calculating means 106, and the selector 108 with respect to the current value calculating means 102 shown in FIG. Yes. That is, only the current value command signal Sia from the deviation current value calculation means 70 is supplied to the limit means 64.
[0086]
Subsequently, an operation mode in the case where the welding apparatus 10 is driven by the control apparatus 40 according to the first comparative example with the same speed schedule and limit schedule (see FIGS. 3A and 3B) as in the above embodiment will be described.
[0087]
In the period from the time point a to d, substantially the same processing is performed as in the case of the above-described embodiment (see FIGS. 3A to 3C).
[0088]
When the rotational speed V of the motor 20 reaches the low speed Vb at the time point d, the speed deviation calculated by the current value calculation means 62 becomes almost zero, so that the value of the current value command signal Sia indicates the speed of the motor 20. It rises to a value (approximately 0) required to maintain the low speed Vb (decreases when viewed as an absolute value). Thereafter, the set limit value supplied as the limit data Di from the main controller 42 to the limit means 64 is changed from the high limit value Ia to the low limit value Ib. Then, the motor 20 is driven at a constant speed at this low speed Vb until the tip of the first gun arm 12 (welding tip 16a) collides with the workpiece W1 (landing region during the period from time point d to time e).
[0089]
When the tip of the first gun arm 12 collides with the workpiece W1, the path of the first gun arm 12 is blocked and its forward speed decreases, and accordingly, the rotational speed V of the motor 20 also decreases. As the rotational speed V of the motor 20 decreases, the rotational speed V falls below the low speed Vb. Therefore, the speed deviation calculating means 68 determines a positive value based on the deviation between the rotational speed V and the low speed Vb. Value velocity deviation data Dσ is output. The deviation current value calculation means 70 outputs a positive current value command signal Sia based on the speed deviation data Dσ to accelerate the motor 20. Along with this, a positive torque is generated in the motor 20 (time point e).
[0090]
After the tip of the first gun arm 12 collides with the workpiece W1 at the time point e, the rotational speed V of the motor 20 rapidly decreases, and accordingly, the speed deviation data Dσ output from the speed deviation calculating means 68 is reduced. The value soars. The value of the current value command signal Sia output from the deviation current value calculation means 70 based on this speed deviation data Dσ also rises rapidly and reaches the upper limit value (low limit value Ib) instantaneously. As a result, the limit means 64 continuously outputs a current value command signal Sib having substantially the same value as the low limit value Ib (period from time point ef to time f).
[0091]
When the motor 20 is stopped, a constant torque based on the current value command signal Sib is generated in the motor 20, and the first gun arm 12 and the second gun arm 14 cause the workpieces W1, W2 to be fixed by this torque. Pressurization is performed by applying pressure (after time f, pressurization region).
[0092]
By the way, in the first comparative example, after the first gun arm 12 collides with the workpiece W1, the value of the current value command signal Sia rises rapidly, so that the motor 20 has substantially the same value as the low limit value Ib. Torque based on the current value command signal Sib is instantaneously generated. As a result, a pressing force is instantaneously applied to the first gun arm 12 and the second gun arm 14, and elastic deformation occurs in the first gun arm 12 and the second gun arm 14 due to this pressing force, and this elastic deformation is restored. (Refer to the period from time point ef in FIGS. 6A to 6C). Therefore, as compared with the case of the above-described embodiment, it takes more time for the first gun arm 12 and the second gun arm 14 to be stopped and to be in a state where welding can be performed. Occurs (see FIGS. 7A and 7B).
[0093]
Next, a second comparative example will be described with reference to FIGS. 7A to 10C.
[0094]
As shown in FIG. 8, in the control device 80 according to the second comparative example, the current value calculation means 84 has a limit from the main controller 42 as compared with the control device 100 according to the present embodiment shown in FIG. The data Di is not supplied.
[0095]
The current value calculation means 84 shown in FIG. 9 limits the increase / decrease rate of the current value command signal Sia from the deviation current value calculation means 70 to a predetermined slope with respect to the current value calculation means 62 shown in FIG. Thus, it is configured to include an increase / decrease rate limiting means 86 that outputs the current value command signal Sig. The increase / decrease rate limiting means 86 starts or stops the process of limiting the increase / decrease rate of the current value command signal Sia based on the timing signal St from the timing detection unit 82.
[0096]
Next, an operation mode when the welding apparatus 10 is driven by the control apparatus 80 according to the second comparative example with the same speed schedule and limit schedule (see FIGS. 3A and 3B) as in the above embodiment will be described.
[0097]
In the period of time points a to d (including time point d), almost the same processing as in the above-described embodiment (see FIGS. 3A to 3C) is performed (except for processing in the selector 108 and the like).
[0098]
After the tip of the first gun arm 12 collides with the workpiece W1 at the time point e, the rotational speed V of the motor 20 rapidly decreases, and accordingly, the speed deviation data Dσ output from the speed deviation calculating means 68 is reduced. The value increases rapidly. Then, the current value command signal Sia output from the deviation current value calculation means 70 on the basis of the speed deviation data Dσ also rises rapidly (period from the time point e to g, the first collision area).
[0099]
When the timing detection unit 82 detects that the rotation speed V of the motor 20 has decreased when the set rotation speed of the motor 20 is the low speed Vb, the timing detection unit 82 performs timing with respect to the increase / decrease rate limiting unit 86 of the current value calculation unit 84. The signal St is output (time point g). The increase / decrease rate limiting unit 86 limits the increase / decrease rate of the current value command signal Sia supplied from the deviation current value calculating unit 70 to a predetermined slope based on the timing signal St from the timing detection unit 82 to obtain a current value. The process of outputting the command signal Sig is started. When the current value command signal Sig reaches the low limit value Ib, the limit means 64 continuously outputs a current value command signal Sib substantially the same value as the low limit value Ib (period from time point g to h). , Second collision area).
[0100]
When the motor 20 stops, a substantially constant torque based on the current value command signal Sib (the same value as the low limit value Ib) is generated in the motor 20, and the first gun arm 12 and the second gun arm 14 are generated by this torque. Pressurizes the workpieces W1 and W2 with a constant pressure (after time point h, a pressurizing region). When the timing detection unit 82 detects that the motor 20 has stopped, the timing detection unit 82 outputs a timing signal St to the increase / decrease rate limiting unit 86 of the current value calculation unit 84. The increase / decrease rate limiting unit 86 stops the process of limiting the increase / decrease rate of the current value command signal Sia supplied from the deviation current value calculating unit 70 based on the timing signal St from the timing detection unit 82.
[0101]
As described above, in the second comparative example, when a decrease in the rotational speed V of the motor 20 is detected when the set rotational speed is the low speed Vb, based on the timing signal St output from the timing detection unit 82. Since the process of limiting the increase / decrease rate of the current value command signal Sia in the increase / decrease rate limiting means 86 is started, it is possible to buffer the impact when the tip of the first gun arm 12 collides with the workpiece W1.
[0102]
However, since the current value command signal Sia rises rapidly after the collision between the first gun arm 12 and the workpiece W1 until the start of the limit of the increase / decrease rate, as in the case of the first comparative example, Vibration occurred in the first gun arm 12 and the second gun arm 14. Therefore, in the second comparative example, the effect of reducing the loss of welding time was not sufficiently obtained as compared with the case of the above-described example (see FIGS. 7A and 7C).
[0103]
As described above, in the control device 100 according to the present embodiment, an excellent vibration suppressing effect is obtained with respect to the first and second comparative examples, and therefore, the welding time is shortened.
[0104]
【The invention's effect】
According to the drive control device and the drive control method for a welding gun arm according to the present invention, the operation of stopping and pressurizing the workpiece after the gun arm is displaced in the direction approaching the workpiece and collides with the workpiece is suitably controlled. As a result, the occurrence of vibration when the gun arm collides with the workpiece is suppressed, and the welding time can be shortened.
[Brief description of the drawings]
FIG. 1 is a block diagram of a control device according to the present embodiment.
FIG. 2 is a block diagram showing a configuration of current value calculation means according to the present embodiment.
FIG. 3 is a graph showing the operation of the motor in this embodiment, FIG. 3A shows the actual rotational speed and set rotational speed of the motor, and FIG. 3B shows the current value and limit of the alternating current to be supplied to the motor. FIG. 3C is a diagram showing the pressure applied to the gun arm.
FIG. 4 is a block diagram of a control device according to a first comparative example.
FIG. 5 is a block diagram showing a configuration of current value calculation means according to a first comparative example.
6 is a graph showing the operation of the motor in the first comparative example, FIG. 6A shows the actual rotational speed and the set rotational speed of the motor, and FIG. 6B shows the current value of the alternating current to be supplied to the motor. FIG. 6C is a diagram showing the applied pressure generated in the gun arm.
FIG. 7A shows the applied pressure generated in the gun arm in this embodiment, FIG. 7B shows the applied pressure generated in the gun arm in the first comparative example, and FIG. 7C shows the applied pressure in the gun arm in the second comparative example. It is a figure which shows the applied pressure which arises.
FIG. 8 is a block diagram of a control device according to a second comparative example.
FIG. 9 is a block diagram showing a configuration of current value calculation means according to a second comparative example.
10 is a graph showing the operation of the motor in the second comparative example, FIG. 10A shows the actual rotational speed and the set rotational speed of the motor, and FIG. 10B shows the current value of the alternating current to be supplied to the motor. FIG. 10C is a diagram showing the applied pressure generated in the gun arm.
[Explanation of symbols]
10 ... welding device 12 ... first gun arm
14 ... Second gun arm 20 ... Motor
42 ... main controller 50 ... speed controller
54 ... Current control unit 60 ... Servo amplifier
64 ... Limit means
68. Speed deviation calculating means (first calculating means)
70: Deviation current value calculation means (first calculation means)
82 ... Timing detection unit (timing detection means)
DESCRIPTION OF SYMBOLS 100 ... Control apparatus 102 ... Current value calculation means
104: Coefficient calculation means (second calculation means)
106: Coefficient current value calculation means (second calculation means)
108 ... selector (switching means)

Claims (8)

A device for controlling the operation of a motor for driving a gun arm for welding to a workpiece when an electrode approaches the workpiece, during a collision and during pressurization,
A main controller for managing the operation schedule of the motor;
Current value calculation means for obtaining a current value to be supplied to the motor based on the operation schedule;
A servo amplifier that supplies a current based on a current value from the current value calculation means to the motor;
The current value calculation means includes first calculation means for obtaining the current value from a deviation between a set speed of the motor and an actual rotation speed;
Second computing means for obtaining the current value by performing a calculation based on a predetermined calculation formula from the set speed, the rotational speed and a predetermined set current value ;
Switching means for switching and outputting the current value obtained by the first computing means and the current value obtained by the second computing means ,
The set current value is an upper limit of a current value supplied to the motor when the electrode approaches the workpiece and a current value to be supplied to the motor during pressurization. Drive control device. In the drive control apparatus of the gun arm for welding of Claim 1 ,
There is provided timing detection means for outputting a signal at a predetermined timing based on the set speed and the rotation speed, and the switching means performs a switching operation based on a signal from the timing detection means. Gun arm drive control device. In the drive control apparatus of the gun arm for welding of Claim 1 or 2 ,
The calculation formula for obtaining the current value in the second calculating means is such that the current value changes in an inclined manner with respect to the change in the rotation speed of the motor, and the current value when the rotation speed is the same as the set speed. The welding gun arm drive control device is configured such that when the rotation speed is 0, the current value becomes the set current value. In the drive control apparatus of the gun arm for welding of Claim 3 ,
When the current value is I, the set speed is V0, the rotation speed is V, and the set current value is Ic,
I = (1−V / V0) × Ic
A drive control device for a welding gun arm. A method for controlling the operation of a motor that drives a gun arm for performing welding on a workpiece,
A series of operations for stopping and pressurizing the workpiece after the gun arm approaches and collides with the workpiece, an approach stage in which the gun arm approaches the workpiece, and a collision stop in which the gun arm collides with the workpiece and stops. And a step for controlling the operation of the motor in a step. In the drive control method of the gun arm for welding according to claim 5 ,
The current value supplied to the motor is determined based on a deviation between the set rotational speed of the motor and the actual rotational speed in the approaching stage,
The welding gun arm drive control method characterized in that, in the collision stop stage, the welding gun arm is obtained from a predetermined rotational speed, an actual rotational speed and a predetermined set current value based on a predetermined calculation formula. The drive control method for a welding gun arm according to claim 6 ,
In the calculation formula, the current value supplied to the motor changes in an inclined manner with respect to a change in the actual rotational speed of the motor, and when the rotational speed is the same as the set rotational speed, the current value becomes 0, The welding gun arm drive control method, wherein the current value becomes the set current value when the motor stops and the actual rotation speed becomes zero. In the drive control method of the gun arm for welding according to claim 7 ,
When the current value supplied to the motor is I, the set current value is Ic, the set rotational speed of the motor is V0, and the actual rotational speed of the motor is V,
I = (1−V / V0) × Ic
A drive control method for a welding gun arm.

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