阅读说明：本技术 推拉送丝控制系统 (Push-pull wire feeding control system ) 是由 R·A·爱尔德里奇 于 2019-06-26 设计创作，主要内容包括：本发明涉及一种推拉送丝控制系统。公开了一种用于控制拉动电机的方法,该方法包括：基于代表由推动电机施加到焊丝上的力的信号与代表所期望由所述推动电机施加到所述焊丝上的力的信号之间的差异,生成误差信号；将代表由所述拉动电机施加到所述焊丝上的力的信号与所述误差信号进行比较,并且基于所述比较来生成输出信号；以及基于所述输出信号来控制所述拉动电机的电枢电流。(The invention relates to a push-pull wire feeding control system. A method for controlling a pull motor is disclosed, the method comprising: generating an error signal based on a difference between a signal representative of a force applied to a welding wire by a push motor and a signal representative of a desired force to be applied to the welding wire by the push motor; comparing a signal representative of a force applied to the welding wire by the pull motor to the error signal and generating an output signal based on the comparison; and controlling an armature current of the pull motor based on the output signal.)

1. A method for controlling a pull motor, the method comprising:

generating an error signal based on a difference between a signal representative of a force applied to a welding wire by a push motor and a signal representative of a desired force to be applied to the welding wire by the push motor;

comparing a signal representative of a force applied to the welding wire by the pull motor to the error signal and generating an output signal based on the comparison; and

controlling an armature current of the pull motor based on the output signal.

2. The method of claim 1, wherein controlling the armature current of the pull motor further comprises:

when the signal representative of the force applied to the welding wire by the pull motor is greater than the error signal, reducing the armature current provided to the pull motor, an

Increasing the armature current provided to the pull motor when the signal representative of the force applied to the welding wire by the pull motor is less than the error signal.

3. The method of claim 1, wherein the signal representative of the force applied to the welding wire by the push motor is based on an armature current of the push motor.

4. The method of claim 1, wherein the magnitude of the error signal is adjusted based on a resistance of a feedback resistor.

5. The method of claim 1, wherein the output signal controls a switch for controlling the armature current provided to the pull motor.

6. The method of claim 1, wherein the output signal is a Pulse Width Modulation (PWM) signal.

7. The method of claim 1, further comprising:

determining when the push motor is in a non-operational state; and

controlling the output signal such that the armature current provided to the pull motor is zero when the push motor is determined to be in a non-operational state.

8. The method of claim 1, wherein the frequency of the output signal is controlled by a resistor-capacitor (RC) network.

9. An apparatus, comprising:

a computer-readable storage medium configured to store computer-executable instructions; and

a processor coupled with the computer-readable storage medium and configured to execute the following computer-executable instructions:

generating an error signal based on a difference between a signal representative of a force applied to a welding wire by a push motor and a signal representative of a desired force to be applied to the welding wire by the push motor;

comparing a signal representative of a force applied to the wire by a pull motor to the error signal and generating an output signal based on the comparison; and

controlling an armature current of the pull motor based on the output signal.

10. The apparatus of claim 9, wherein controlling the armature current of the pull motor further comprises:

when the signal representative of the force applied to the welding wire by the pull motor is greater than the error signal, reducing the armature current provided to the pull motor, an

Increasing the armature current provided to the pull motor when the signal representative of the force applied to the welding wire by the pull motor is less than the error signal.

11. The apparatus of claim 9, wherein the signal representative of the force applied to the welding wire by the push motor is based on an armature current of the push motor.

12. The apparatus of claim 9, wherein the magnitude of the error signal is adjusted based on a resistance of a feedback resistor.

13. The apparatus of claim 9, wherein the output signal controls a switch for controlling the armature current provided to the pull motor.

14. The apparatus of claim 9, wherein the output signal is a Pulse Width Modulation (PWM) signal.

15. The apparatus of claim 9, wherein the computer-executable instructions further comprise:

determining when the push motor is in a non-operational state; and

controlling the output signal such that the armature current provided to the pull motor is zero when the push motor is determined to be in a non-operational state.

16. The apparatus of claim 9, wherein a frequency of the output signal is controlled by a resistor-capacitor (RC) network.

17. One or more non-transitory computer-readable storage media encoded with instructions that, when executed by a processor, cause the processor to:

generating an error signal based on a difference between a signal representative of a force applied to a welding wire by a push motor and a signal representative of a desired force to be applied to the welding wire by the push motor;

comparing a signal representative of a force applied to the wire by a pull motor to the error signal and generating an output signal based on the comparison; and

controlling an armature current of the pull motor based on the output signal.

18. The one or more non-transitory computer-readable storage media of claim 17, wherein the instructions further cause the processor to:

when the signal representative of the force applied to the welding wire by the pull motor is greater than the error signal, reducing the armature current provided to the pull motor, an

Increasing the armature current provided to the pull motor when the signal representative of the force applied to the welding wire by the pull motor is less than the error signal.

19. The one or more non-transitory computer-readable storage media of claim 17, wherein the signal representative of the force applied by the push motor onto the welding wire is based on an armature current of the push motor.

20. The one or more non-transitory computer-readable storage media of claim 17, wherein the magnitude of the error signal is adjusted based on a resistance of a feedback resistor.

Technical Field

The present disclosure relates to a push-pull wire feed control system.

Background

Push-pull wire feed systems may be used to advance welding wire (wire) in a variety of applications, such as welding. The push-pull wire feeding system comprises a push motor and a pull motor. The push motor may be located near a source of welding wire (such as a wire drum). The push motor applies a force to the welding wire to push the welding wire through the welding wire conduit. The pull motor may be located at or near the end of the wire guide. For example, the pull motor may be located in or near the weld head in a welding application. The pull motor applies a force to the wire to pull the wire through the conduit.

Drawings

FIG. 1 illustrates a push-pull wire feed system including a push-pull motor control system according to an example embodiment.

FIG. 2 is a circuit diagram of a push-pull motor control system for controlling a pull motor according to an example embodiment.

FIG. 3 is a block diagram of a computing system for controlling a pull motor according to an example embodiment.

FIG. 4 is a graph of push motor armature current values and pull motor armature current values over a period of time according to an example embodiment.

FIG. 5 is a flowchart of a method for controlling a pull motor in a push-pull wire feed system according to an example embodiment.

Detailed Description

SUMMARY

The present disclosure relates generally to controlling the force applied to a welding wire by a pull motor in a push-pull wire feed system. The push-pull wire feed system may include a push motor and a pull motor. The push motor armature current and the pull motor armature current represent the force applied to the welding wire by the push motor and the pull motor, respectively. The system compares the signal representative of the propel motor force to a signal representative of a desired propel motor force to generate an error signal. The system compares the error signal to a signal representative of the pull motor force. Based on the comparison, the system generates an output signal for controlling the current of the armature of the pull motor. For example, when the signal representing the pull motor force is greater than the error signal, the output signal may cause the pull motor armature current to decrease. Conversely, when the signal representing the pull motor force is less than the error signal, the output signal causes the pull motor armature current to increase.

Example embodiments

Referring to FIG. 1, a push-pull wire feed system 100 including a push-pull motor control system 102 is shown according to an example embodiment. Push-pull wire feed system 100 may include a wire source 104, such as a spool of wire. The wire source 104 may include a wire to be used in, for example, a welding application, such as wire 106. Push-pull wire feed system 100 may also include a push motor 108 and a pull motor 110. The push motor 108 and the pull motor 110 may apply a force to the welding wire 106 to advance the welding wire 106. For example, the push motor 108 may apply a force to the welding wire 106 to push the welding wire 106 toward the pull motor 110, and the pull motor 110 may apply a force to the welding wire 106 to pull the welding wire 106 toward itself. Push-pull wire feed system 100 may also include a push motor biasing member 112 and a pull motor biasing member 114. Pushing the motor biasing member 112 and pulling the motor biasing member 114 may bias the welding wire 106 to a desired position. For example, pushing the motor biasing member 112 may position the welding wire 106 such that the welding wire 106 enters the wire guide 116. The wire guide 116 may be positioned between the push motor 108 and the push motor biasing member 112 and the pull motor 110 and the pull motor biasing member 114. The wire guide 116 may define the path taken by the wire 106 from the push motor 108 to the pull motor 110. It should be appreciated that the wire guide 116 may be any length and may also include any number of bends or curves.

In welding applications, the supplied welding wire 106 may have a small diameter and/or be relatively flexible. Feeding the welding wire 106 through the wire guide 116 may be problematic, particularly if the wire guide 116 is relatively long and/or includes numerous bends or curves. For example, the force required to push the welding wire 106 through the wire guide 116 using the push motor 108 may be greater than the breaking strength of the welding wire 106. In such a case, the welding wire 106 may buckle at the entry point of the wire guide 116, causing tangling of the welding wire (commonly referred to as bird nesting). While lower friction wire catheters tend to reduce undesirable bird nesting, problems still exist.

The pull motor 110 may be used to reduce the amount of force that needs to be applied to the welding wire 106 by the push motor 108 to pass the welding wire 106 through the guide tube 116. There are two variants of systems comprising a pull motor: a push-pull wire feed system (not shown) and a push-pull wire feed system (such as push-pull wire feed system 100). In a pull-push wire feed system, the pull motor may determine the speed at which the wire is fed, while the push motor may be torque limited. Because the push motor is torque limited, the push motor can be used to assist the pull motor without exerting enough force to cause the wire to catch and create a bird's nest. One drawback of pull and push wire systems in welding applications is that the pull motor applies a large portion of the force to the wire. However, as mentioned, the pull motor must be kept relatively small because it is located in, for example, a welding torch. Such size limitations may prevent the pull motor from applying sufficient force to the wire and, thus, cause the wire feed to be slower than desired. Another disadvantage is that, also because of size limitations, it is difficult to include a tachometer in the pull motor where the torch is mounted, and thus the wire feed is less accurate.

In push-pull wire feed system 100, the wire feed speed of wire 106 is determined by push motor 108. The push motor 108 is typically regulated by a tachometer, which enables more accurate wire feed delivery. In push-pull wire feed system 100, pull motor 110 applies force to wire 106 to relieve some of the load from push motor 108. To relieve the load from the push motor 108, the pull motor 110 may be matched in speed characteristics to the push motor 108.

In both push and pull wire systems 100, any calibration performed for a given push motor and pull motor configuration is static. In other words, once the wire feed system is calibrated, the wire feed system does not accommodate changes in the limits of the wire conduit (such as conduit wear, conduit length, bends in the conduit, etc.) or changes in the torch in, for example, welding applications. As a result, any changes (such as different welding torches or different wire guides) require manual recalibration.

Turning to FIG. 2 with continued reference to FIG. 1, a circuit 200 of a push-pull wire feed system 100 is shown including a push-pull motor control system 102 for controlling a pull motor 110 according to an exemplary embodiment. The circuit 200 may quantify the force applied to the wire 106 by the push motor 108 to control the force applied to the wire 106 by the pull motor 110. By controlling the force applied by the pull motor 110, the circuit can adjust the force applied to the wire 106 by the push motor 108. The push motor armature current is proportional to the force applied to the welding wire 106 by the push motor 108. Based on the push motor armature current, the push-pull motor control system 102 may determine whether more or less assistance (i.e., force applied to the welding wire 106) is needed from the pull motor 110. The pull motor 110 may be controlled by, for example, a current mode controller (as described with respect to fig. 2) or a computing system (as described with respect to fig. 3). As with the push motor 108, the pull motor armature current is proportional to the force applied to the wire 106 by the pull motor 110. The push-pull motor control system 102 is designed so that the speed of the pull motor can be adjusted to match the speed of the push motor 108 while the wire 106 is being fed.

More specifically, the circuit 200 may include a main control Printed Circuit Board (PCB) 201. PCB 201 is shown in simplified form as including switch 202. For example, the switch 202 may be a Metal Oxide Semiconductor Field Effect Transistor (MOSFET). It should be understood that the MOSFET may be an n-type or p-type MOSFET. Other circuit elements, such as Bipolar Junction Transistors (BJTs), may also be used. The switch 202 may provide a push motor Pulse Width Modulation (PWM) signal 203 to the push-pull motor control system 102, as described in more detail herein. In some embodiments, a tachometer (not shown) may also be included within the PCB 201. The PCB 201 may also supply a positive power supply 204 and a negative power supply 205. For example, as shown in fig. 2, the positive power supply 204 is 60V and the negative power supply is 0V. However, it should be understood that any value of the positive power supply 204 and the negative power supply 205 may be used. The PCB 201 may be connected to a connector 206, which connector 206 may have a connection portion 207 and 210. The positive power supply 204 may be connected to the connection 207, the push motor PWM signal 203 may be connected to the connection 208, and the negative power supply 205 may be connected to the connection 210.

The circuit 200 may also include a connector 211 that may be connected to the push motor 108. The connector 211 may include a connection portion 212 and a connection portion 213. The connection 212 may be connected to the connection 207 and the positive power supply 204. The connection 212, and thus the positive power supply 204, may be connected to the positive terminal of the push motor 108, while the connection 213 may be connected to the negative terminal of the push motor 108. Thus, the push motor armature current may flow to the positive terminal of the push motor 108 through the connection 212. The push motor armature current may return from the push motor 108 to the connection 213 via the negative terminal of the push motor 108.

The push motor armature current may then be input to a hall effect sensor 214, such as the open loop hall effect sensor shown in fig. 2. The hall effect sensor 214 can include an input 215 at which current enters the hall effect sensor 214 and an output 216 at which current exits the hall effect sensor 214. Based on the push motor current, the hall effect sensor 214 can output a signal on an output 217 that represents the current entering on an input 215 and leaving on an output 216. Here, the push motor armature current enters at input 215 and exits at output 216. Thus, the output 217 may output a signal 218 proportional to the push motor armature current. For example, the signal 218 may be a voltage signal. In this embodiment, the Hall effect sensor 214 produces 0.4V for every 1A of push motor armature current. Thus, the signal 218 on the output 217 may be a voltage representative of the current pushing the motor armature. Because the push motor armature current is representative of the force applied by the push motor 108 to the wire 106, the signal 218 on the output 217 is also representative of the force applied by the push motor 108 to the wire 106. It should be appreciated that the hall effect sensor 214 may output any signal representative of the push motor armature current and the force applied to the wire 106 by the push motor 108, not just a voltage. However, for exemplary purposes only, the signal 218 on the output 217 will be described as a voltage 218 representative of the push motor force.

A voltage 218 representative of the push motor force may be input into the negative terminal 219 of the operational amplifier 220. The gain of operational amplifier 220 may be set to-1. In other words, the operational amplifier 220 may invert the voltage 218 representative of the push motor force to produce an inverted voltage 221 representative of the push motor force. An inverse voltage 221 representative of the push motor force may be provided to the current mode PWM controller 222, such as from TexasUC 3843. The current mode PWM controller 222 may include four input terminals 223-. An inverted voltage 221 representative of the push motor force may be received at an input terminal 223 of the current mode PWM controller 222. The input terminal 223 of the current-mode PWM controller 222 mayTo be a summing point. The inverse voltage 221 representing the push motor force may be summed with a signal 229 representing the desired push motor force. For exemplary purposes only, the signal 229 representative of the desired push motor force will be described as a voltage. The voltage 229 representing the desired push motor force may be controlled by, for example, a variable resistor 230, such as a potentiometer. A first terminal of variable resistor 230 may be connected to a positive power supply and a second terminal of variable resistor 230 may be directly or indirectly connected to input terminal 223. The value of the variable resistor 230 may be predetermined, such as at the factory. Alternatively, the value of the variable resistor 230 may be set by a user of the push-pull wire feed system 100 based on, for example, a particular application.

Another signal that may be summed at the summing junction at input terminal 223 is an error or feedback signal 231 generated by the current mode PWM controller 222 and output on output terminal 227, as described in more detail below. The error signal 231 may be based at least in part on a difference between the inverted voltage 221 representative of the push motor force and a voltage 229 representative of the desired push motor force.

The summed signal received at input terminal 223 may be a first input to an amplifier (not shown) included in the current mode PWM controller 222. The second input to the amplifier included in the current mode PWM controller 222 may be a constant voltage, such as 2.5V. In one embodiment, the constant voltage may be an internal reference for the current mode PWM controller 222. The amplifier included in the current mode PWM controller 222 may have a gain characteristic that compares the input at the input terminal 223 with a constant voltage (here, 2.5V). The output of the amplifier may be provided on the output terminal 227 of the current mode PWM controller 222 as an error or feedback signal 231. As described above, the error signal 231 may be provided to a summing junction. The error signal 231 may be provided to the summing junction via a resistor 232. The resistor 232 may be used to control the gain of the amplifier included in the current mode PWM controller 222. In other words, the resistor 232 may be used to adjust the amplitude of the error signal. Thus, the resistance of the resistor 232 may determine how closely the current mode PWM controller 222 attempts to adjust the current drawn by the motor armature, as described herein.

With respect to the pull motor armature current, the pull motor armature current may be controlled by a switch 233 (such as a MOSFET), as shown in fig. 2. The circuit 200 includes a connector 234 that can be connected to the pull motor 110. Connector 234 may include a connection portion 235 and a connection portion 236. The positive power supply 204 may be connected to the positive terminal of the pull motor 110 through a connection 235 of the connector 234, while a connection 236 of the connector 234 may be connected to the negative terminal of the pull motor 110. Thus, the pull motor armature current may flow to the positive terminal of the pull motor 110 through the connection 235 of the connector 234. The pull motor armature current may return from the pull motor 110 to the connection 236 of the connector 234 via the negative terminal of the pull motor 110. When the switch 233 is closed or enabled when a MOSFET is used, a pull motor armature current can flow through the switch 233. However, when the switch 233 is open or deactivated when a MOSFET is used, the pull motor armature current may be reduced. When the switch 233 is open or deactivated for a sufficient amount of time, the pull motor armature current may go to zero. The pull motor armature current may be converted to a signal 237 representative of the pull motor force applied to the wire 106. This transformation may occur at a 1:1 ratio. For exemplary purposes only, the signal 237 representative of the pull motor force is described herein as a voltage.

A voltage 237 representative of the pull-up motor force may be provided as an input to the current mode PWM controller 222 at the input terminal 224. The current mode PWM controller 222 may compare a voltage 237 representative of the pull motor force to an error or feedback signal 231. In some embodiments, a portion of the error signal 231 (such as 1/3) may be compared to a voltage 237 representative of the pull motor force. The result of this comparison may be provided at the output terminal 228 of the current mode PWM controller 222 as the output signal 238. The output signal 238 may be provided to the switch 233 to control when the switch 233 is activated or deactivated. For example, when switch 233 is a MOSFET, output signal 238 can be provided to the gate of the MOSFET, which controls when the MOSFET is enabled or disabled. The output signal 238 may go low when the voltage 237 representing the pull motor force is greater than or exceeds the error signal 231 or a predetermined portion of the error signal 231. Conversely, the output signal 238 may go high when the voltage 237 representing the pull motor force is less than the error signal 231 or a predetermined portion of the error signal 231. Thus, the output signal 238 may be a pulsed output. The duty cycle of the output signal 238 may be the time it takes for the voltage 237 representing the pull-motor force to exceed the error signal 231 or a predetermined portion of the error signal 231.

More particularly, when the voltage 237 representing the pull motor force is greater than the error signal 231, the pull motor armature current may be too high. As described above, when this occurs, the output signal 238 may go low. The output signal 238 going low may cause the switch 233 to become deactivated, thereby causing an open circuit that pulls the motor armature current. This causes the pull motor 110 to freewheel through diode 251 and the pull motor armature current decreases.

The output signal 238 may go high when the pull-motor armature current is reduced to a level such that the voltage 237 representing the pull-motor force is less than the error signal 231. When output signal 238 goes high, switch 233 may become enabled. When the switch 233 is activated, the pull motor armature current circuit is closed, thereby increasing the pull motor armature current. This cycle is repeated as the voltage 237 representing the pull motor force increases or decreases relative to the error signal 231.

The frequency of the output signal 238 may be determined by the input terminal 225. For example, a resistor-capacitor (RC) time constant may be used to set the frequency of the output signal 238. When the RC time constant is used to set the frequency of the output signal 238, a capacitor (such as capacitor 249) may be connected to ground, and a resistor (such as resistor 250) may be connected to the input terminal 226. The capacitance of capacitor 249 and the resistance of resistor 250 determine the RC time constant, which sets the frequency of output signal 238.

In some embodiments, the operation of the pull motor 110 may be disabled. For example, the pull motor 110 may be disabled when, for example, the push motor 108 is not running. In general terms, the comparator may be used to disable the pull motor 110 when the push motor 108 is not running and to enable the pull motor 110 when the push motor 108 is running.

More specifically, the comparator 239 may receive inputs on the first connection portion 240 and the second connection portion 241. As described above, the first connection 240 may receive the push motor PWM signal 203 from the PCB 201. When the push-pull wire feed system 100 is on but the push motor 110 is not already running, the push motor PWM signal 203 may be high. The output 242 of the comparator 239 may also be driven high when the push motor PWM signal 203 is high. The output 242 of the comparator 239 may be received at the input terminal 224 of the current mode PWM controller 222 (i.e., the input terminal that receives the voltage 237 representing the pull-up motor force). As described above, when the voltage 237 representing the pull-motor force is greater than the error signal 231, the output signal 238 is driven low. Thus, the output signal 238 is low because the voltage 237 representing the pull-up motor force is driven high by the output 242. When the output signal 238 is low, the switch 233 is deactivated and the pull motor armature current is reduced. However, because the pull motor armature current is zero since the push pull wire feed system 100 has just been opened, the pull motor armature current is prevented from increasing, thereby disabling the pull motor 110.

Conversely, when the push motor 108 is running, the push motor PWM signal 203 may be low. When the push motor PWM signal 203 is low, the capacitor 243 may discharge through the resistor 244 and the diode 245. The discharge rate of the capacitor 243 may be such that the value of the first connection portion 240 of the comparator 239 does not exceed the value of the second connection portion 241 of the comparator 239. The value of the signal at the second connection portion 241 of the comparator 239 may be a constant voltage, such as 2.5V. The discharge of the capacitor 243 may cause the output 242 of the comparator 239 to be driven low. This results in controlling the pull motor armature current as described above.

The push-pull motor control system 102 may provide power to each component within the push-pull motor control system 102 via a power inverter 246. The power converter 246 may be, for example, a DC-DC power converter. The power converter 246 may receive as inputs the positive power supply 204 and the negative power supply 205. As described above, the positive power supply 204 is 60V and the negative power supply 205 is 0V. The power converter 246 may convert the positive power supply 204 and the negative power supply 205 into a converted positive power supply 247 and a converted negative power supply 248. In this example, the transformed positive power supply 247 is 12V and the transformed negative power supply 248 is-12V. The transformed positive power supply 247 and the transformed negative power supply 248 may be used to power other components of the push-pull motor control system 102, such as the hall effect sensor 214, the operational amplifier 220, the current mode PWM 222, and the comparator 239.

Thus, the circuit 200 provides a technique for controlling the pull motor armature current in response to a deviation of the push motor armature current from a desired push motor armature current. These techniques enable the push-pull wire feed system 100 to accommodate changes in the wire guide 116 and/or changes in the pull motor 110 without requiring manual reconfiguration of the push-pull wire feed system 100.

Turning to FIG. 3 with continued reference to FIG. 1, a block diagram of a computing system 300 for controlling pull motor armature current is shown, according to an example embodiment. Computing system 300 may include a processor 302, a storage medium 304, an input 306, and an output 308. It should be understood that any number of processors 302, storage media 304, inputs 306, and outputs 308 may be included. A first communication bus 310 may be used to enable communication between the processor 302, the storage medium 304, the input 306, and the output 308. The storage medium 304 may include pull motor control logic 312, as described in more detail herein. The processor 302 may be configured to execute instructions stored in the storage medium 304, such as the pull motor control logic 312. The computing system 300 may be connected to the push motor 108 and the pull motor 110 via a second communication bus 312. The input 306 may be configured to receive data such as a signal representative of the force applied to the wire 106 by the push motor 108, a signal representative of the force expected to be applied to the wire 106 by the push motor 108, and a signal representative of the force applied to the wire 106 by the pull motor 110. The output 308 may be configured to output a signal that increases or decreases the pull motor armature current.

For example, the computing system 300 may receive a signal from the push motor 108 representative of the push motor armature current. As described above, the push motor armature current may represent the force applied to the welding wire 106 by the push motor 108. The processor 302 may be configured to transform a signal representative of the push motor armature current into a signal representative of the force applied by the push motor 108 to the welding wire 106. The computing system 300 may also receive a signal representative of a desired force to be applied to the wire 106 by the push motor 108. The pull motor control logic 312 may cause the processor 302 to calculate a difference between the signal representative of the force applied to the wire 106 by the push motor 108 and the signal representative of the force expected to be applied to the wire 106 by the push motor 108. The difference may be an error or a feedback signal.

The computing system 300 may also receive as input a signal representative of the force applied to the wire 106 by the pull motor 110. The signal representative of the pull motor force may be, for example, the pull motor armature current. The pull motor control logic 312 may cause the processor 302 to compare the signal representative of the pull motor force to an error or feedback signal. In one embodiment, the pull motor control logic 312 may cause the processor 302 to compare the signal representative of the pull motor force to a portion of the error (such as 1/3). Based on the comparison, the processor 302 may calculate an output signal. The output signal may control the pull motor armature current. For example, when the signal representative of the pull motor force is less than the error signal, the output signal may cause the pull motor armature current to increase without specifying an accurate pull motor armature current. When the signal representing the pull motor force is greater than the error signal, the output signal also causes the pull motor armature current to decrease without specifying an accurate pull motor armature current.

The computing system 300 may also receive as input a signal indicating whether the push motor 108 is operating. For example, the signal indicating whether the push motor 108 is operating may be a PWM signal. The computing system 300 may output a signal to enable or disable the pull motor 110 based on the signal indicating whether the push motor 108 is running. For example, when the signal indicates that the push motor 108 is not running, the computing system 300 may output a signal that keeps the pull motor armature current at zero, thereby disabling the pull motor 110. Conversely, when the signal indicates that the push motor 108 is running, the computing system 300 may output a signal that enables the pull motor current by controlling the pull motor armature current as described above.

Turning to fig. 4 with continued reference to fig. 2, a graph 400 of signal values over time is shown in accordance with an example embodiment. The graph 400 may be obtained using, for example, an oscilloscope. Graph 400 includes an inverse voltage 221 representing a push motor force and a voltage 237 representing a pull motor force. The inverse voltage 221 representing the push motor force is centered at a division (division)402 and the voltage 237 representing the pull motor force is centered at a division 404. Each vertical division of the inverse voltage 221 representing the push motor force is 2V per division, while each vertical division of the voltage 237 representing the pull motor force is 500mV per division. The horizontal time division represents 40 milliseconds.

Graph 400 illustrates a response to an operating torch. For the inverse voltage 221 representing the push motor force, which rapidly drops to 2V, there is an initial 8V peak. After approximately 80 milliseconds, the push motor has accelerated to the set speed, and as the acceleration of the push motor 108 decreases, the inverse voltage 221, representing the push motor force, decreases. After approximately 200 milliseconds, the inverse voltage 221, representing the push motor force, has stabilized to approximately 2.5V.

The voltage 237 representing the pull motor force changes in response to a change in the inverse voltage 221 representing the push motor force. For example, as the magnitude of the inverse voltage 221 representing the push motor force increases, the voltage 237 representing the pull motor force also increases. In such a case, the voltage 237 representing the pull motor force is increased such that the push motor 108 does not apply an excessive force to the wire 106, which could, for example, cause the wire 106 to buckle and cause bird nests. Conversely, when the magnitude of the inverse voltage 221 representing the push motor force decreases, the voltage 237 representing the pull motor force also decreases. In such a case, the push motor 108 applies less force to the wire 106. Thus, less assistance from the pull motor 110 is required to reduce the risk of the push motor 108 applying excessive force to the wire 106.

Turning to FIG. 5 with continued reference to FIGS. 2 and 3, a flow diagram of a method 500 for controlling pull motor armature current in a push-pull wire feed system 100 is shown, according to an exemplary embodiment. The method 500 may be performed by the current mode PWM controller 222 or the computing system 300. For exemplary purposes only, the operation of the method 500 is described with reference to the current mode PWM controller 222. At operation 502, the current mode PWM controller 222 may generate an error signal 231. The error signal 231 may be generated based on a difference between the signal representative of the force applied to the wire 106 by the push motor 108 and the signal representative of the force expected to be applied to the wire 106 by the push motor 108. For example, the difference may be received as an input at input terminal 223, as described above with reference to fig. 2.

At operation 504, the current mode PWM controller 222 may compare the signal 237 representative of the pull motor force to the error signal 231. The output signal 238 may be based on the comparison. For example, the current mode PWM controller 222 may compare the signal 237 representing the pull motor force to the error signal 231 or a portion of the error signal 231 (such as 1/3). When the signal 237 representing the pull motor force is less than the error signal 231, the current mode PWM controller 222 may cause the output signal 238 to be high. When the signal 237 representing the pull motor force is greater than the error signal 231, the current mode PWM controller 222 may cause the output signal 238 to be low.

At operation 506, the output signal 238 generated in operation 504 may be used to control the pull motor armature current, and thus the pull motor force applied to the wire 106. For example, as depicted in fig. 2, the output signal 238 may control a switch 233, the switch 233 controlling the pull motor armature current. In one embodiment, when the output signal 238 is high, the switch 233 may be enabled, thereby causing the pull motor armature current to increase. However, when the output signal 238 is low, the switch 233 may be deactivated, thereby causing the pull motor armature current to decrease.

In summary, a method for controlling a pull motor is disclosed. The method comprises the following steps: generating an error signal based on a difference between the signal representative of the force applied to the welding wire by the push motor and a signal representative of a desired force to be applied to the welding wire by the push motor; comparing a signal representative of a force applied to the wire by the pull motor to the error signal and generating an output signal based on the comparison; and controlling an armature current of the pull motor based on the output signal.

More particularly, the method may further comprise: reducing the armature current provided to the pull motor when the signal representative of the force applied to the welding wire by the pull motor is greater than the error signal; and increasing the armature current provided to the pull motor when the signal representative of the force applied to the welding wire by the pull motor is less than the error signal.

In addition, the signal representative of the force applied to the welding wire by the push motor is based on the armature current of the push motor.

In addition, the magnitude of the error signal is adjusted based on the resistance of the feedback resistor.

Also, the output signal may control a switch, such as a MOSFET, that controls the armature current provided to the pull motor, which may be a pulse width modulated signal.

Further, the method may further include determining when the push motor is in a non-operational state. The method may control the output signal such that the armature current provided to the pull motor is zero when the push motor is in a non-operational state.

Finally, the output signal may have a frequency controlled by a resistor-capacitor network.

In another embodiment, an apparatus for controlling current to a pulling motor armature is disclosed. More particularly, the apparatus may include a computer-readable storage medium configured to store computer-executable instructions and a processor coupled with the computer-readable storage medium and configured to execute the computer-executable instructions. The computer-executable instructions may include: generating an error signal based on a difference between the signal representative of the force applied to the welding wire by the push motor and a signal representative of a desired force to be applied to the welding wire by the push motor; comparing a signal representative of a force applied to the wire by the pull motor to the error signal and generating an output signal based on the comparison; and controlling an armature current of the pull motor based on the output signal.

In yet another embodiment, one or more non-transitory computer-readable storage media encoded with instructions for execution by a processor are disclosed. In particular, the instructions cause the processor to: generating an error signal based on a difference between the signal representative of the force applied to the welding wire by the push motor and a signal representative of a desired force to be applied to the welding wire by the push motor; comparing a signal representative of a force applied to the wire by the pull motor to the error signal and generating an output signal based on the comparison; and controlling an armature current of the pull motor based on the output signal.

The above description is for the purpose of example only. Although the technology is illustrated and disclosed herein as embodied in one or more specific examples, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein within the scope and range of equivalents of the claims.