Patent Publication Number: US-10307854-B2

Title: Method for selection of weld control algorithms

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. non-provisional application Ser. No. 13/481,066 filed on May 25, 2012, entitled “METHOD FOR SELECTION OF WELD CONTROL ALGORITHMS,” which claims the benefit of U.S. Provisional Patent Application No. 61/490,329 filed May 26, 2011. The disclosures of the above applications are incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     The present application is related to a welding system configured to switch between weld control algorithms. 
     SUMMARY 
     Welding control systems may not provide for optimal automatic control of short-circuit, globular, and spray transfer, and spatter, base material penetration, bead shape and heat input. Welding control system may also fail to provide optimal automatic control in other welding processes, including flux core arc welding, shielded metal arc welding, and gas tungsten arc welding. A system is contemplated herein which may improve these conditions by switching weld control algorithms. 
     In some implementations, a system for generating a weld is provided. A power circuit generates welding output power for a welding process. A control circuit is in communication with the power circuit. The control circuit receives a selected value of a magnitude of an output voltage. The control circuit selects a first weld control algorithm from the plurality of weld control algorithms when the magnitude of the voltage is in a first range of values, and selects a second weld control algorithm from the plurality of weld control algorithms when the magnitude of the voltage is in a second range of values. 
     In some implementations, a method for generating a weld is provided. The method includes receiving a selection of a magnitude of a voltage. The method further includes selecting a first weld control algorithm when the magnitude of the voltage is in a first range of values. The method further includes selecting a second weld control algorithm when the magnitude of the voltage is in a second range of values. The method further includes generating welding output power based on the first and second weld control algorithms. 
     Further objects, features and advantages of this application will become readily apparent to persons skilled in the art after a review of the following description, with reference to the drawings and claims that are appended to and form a part of this specification. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
         FIG. 1  is a schematic view of a welding system; 
         FIG. 2 a    is a perspective view of a housing which contains the welding system of  FIG. 1 ; 
         FIG. 2 b    is a front view of an interface on the housing of  FIG. 2   a;    
         FIG. 3  is a flow chart illustrating a method for automatically selecting weld control algorithms; and 
         FIG. 4  is a schematic view of a processing system for implementing the methods described herein. 
     
    
    
     It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. 
     DETAILED DESCRIPTION 
     The term “substantially” used herein with reference to a quantity or mathematical relationship includes (1) a variation in the recited quantity or relationship of an amount that is insubstantially different from a recited quantity or relationship for an intended purpose or function, or (2) a variation in the recited quantity or relationship of an amount that produces the same quality. 
     Now referring to  FIG. 1 , a power supply for a welding system  100  is provided. The power supply  110  receives input power  112  which may be an alternating current power line, for example a 220 volt AC power line. However, it is understood that the power supply  110  may be adaptable to receive a range of voltages, for example between 187 to 276 volts AC. In addition, it may also be possible to configure the power supply for other voltage ranges depending on the application and required welding output power. The power supply  110  provides a direct current power output voltage  114  that may be used as a welding output power  116 . In some implementations, the power supply  110  may be used for stick welding (also known as Shielded Metal Arc Welding or SMAW) or various other welding applications such as MIG (Metal Inert Gas, also known as gas metal arc welding or GMAW), flux core arc welding, TIG (tungsten inert gas welding, also known as Gas Tungsten Arc Welding or GTAW), plasma arc, or other welding processes. Therefore, in one example the current return lead of the welding output power  116  may be provided to a part  118  that is to be welded, and the supply voltage may be provided to an electrode, for example a stick  120  or wire  122 . Therefore, as the stick  120  comes in contact with the part  118  an arc may be formed that melts both the base metal and electrode and cooperates to form a weld. In other implementations, the output voltage may be provided through a wire  122  which may be continuously fed to the part to form a continuous weld. In TIG mode the electrode is not melted, and generally only the base metal is melted. 
     The power supply  110  may control the output voltage and the output current, as well as the feeding of the wire to optimize the welding process. In addition, the power supply  110  may be connected to one group of accessories  124  including for example a remote wire feeder  126 , a spool gun  128 , or a push/pull gun  130 . Further, the power supply  110  may be connected to other groups of accessories  132 , for example through an 8-pin connector. The second group of accessories  132  may include a MIG gun  134 , a smart gun  136 , a foot pedal  138 , a pendant  140 , a TIG gun  142 , and/or a remote control/trigger  144 . 
     Within the power supply  110 , the input power  112  may be provided to a circuit breaker or switch  154 . Power may be provided from the circuit breaker  154  to a power circuit  150 . The power circuit  150  may condition the input power to provide a welding output power  116 , as well as, for powering various additional accessories to support the welding process. The power circuit  150  may also be in communication with the control circuit  152 . The control circuit  152  may allow the user to control various welding parameters, as well as, providing various control signals to the power circuit  150  to control various aspects of the welding process. The power from the circuit breaker  154  may be provided to an EMI filter  156  of the power circuit  150 . Power is provided from the EMI filter  156  to an input bridge  158 . Power may be provided from the input bridge  158  to a conditioning circuit  162 . The conditioning circuit  162  may include a boost circuit, a transformer, as well as a power factor correction circuit. Power is provided from the conditioning circuit  162  to the inverter  160  where the power is converted to a DC signal  114  thereby providing welding output power  116 . Power may also be provided to a bias circuit  170  to power a number of accessories internal or external to the power supply  110  that facilitate operation of the power supply and welding process. For example, the bias circuit  170  may provide power to gas solenoid valves  172 , fans  174 , as well as, other accessory devices. In addition, power is provided to a motor drive circuit  164  that is in communication with a motor  166 . The motor  166  may be in communication with a feed mechanism  168  configured to feed wire  122  to a weld gun for use in creation of the weld. The control circuit  152  may provide control signals to any of the previously mentioned circuits in the power circuit  150  to optimize the weld process and performance of the power supply  110 . The control circuit  152  may include a pulse width modulator  182  and a processor  184  for analyzing various weld characteristics and calculating various weld parameters according to user settings, as well as, various feedback signals. In addition, an interface circuit  186  may be provided to control a display  188  that may provide information to the user of the welding system. The display  188  may include an LED display, a LCD display, or various other known display technology. The display may provide various menu choices to the user, as well as, providing various feedback on the welding process including the values of various parameters or graphs of previous welding characteristics. The controls  190  may also be in communication with the interface circuit  186  to allow the user to provide input such as various welding parameters to control the operation of the welding process. 
     The power supply  110  may further include a voltage reducing device (VRD) circuit  192 , a low-power circuit that detects contact between the part  118  to be welded and the electrode. When an open circuit condition is detected between the electrode and the work piece, the VRD circuit  192  may reduce the maximum open circuit voltage to safe levels. When contact is made and/or the load is below a threshold resistance, the VRD circuit  192  may no longer reduce the voltage and thus may allow the welding system  100  to operate at full power. The VRD circuit  192  may be in communication with a timer  194 . The timer  194  may be implemented as software as part of the control circuit  152 , or may be comprised of an electronic circuit. 
     Now referring to  FIG. 2 a   , a housing  200  is provided that may be implemented with the welding system  100 . The housing  200  may contain the power supply  110 , and may further include a user interface  202  and a front connection panel  204 . The front connection panel  204  may, for example, be used for connecting the power supply  110  to the first and second groups of accessories  124  and  132 , as discussed above. 
     Now referring to  FIG. 2 b   , a particular implementation of a user interface  202  is provided that may include various inputs selectable by a user and various indicators and displays. A power indicator  210  may indicate when the power supply  110  is receiving the input power  112 . A fault light  220  may indicate when the welding process has entered a fault condition. A VRD “on” indicator  230  may indicate when the VRD is on, and a VRD “off” indicator  232  may indicate when the VRD is off. 
     A mode selection input  240  may allow the user to select a desired welding process. The mode selection input  240  may be a button which when pressed causes the power supply  100  to cycle through and select a welding process. Three welding process indicators  242 ,  244 ,  246  may respectively light upon selection of, for example, MIG, TIG, or stick welding. The MIG selection provides a suitable configuration for both gas metal arc welding and flux core arc welding. 
     A trigger interlock input  270  may allow a user to select between 2 T and 4 T modes for MIG, TIG and stick welds that are activated via an electric switch. The 2 T mode allows the user to push and hold the switch to activate and release the switch to deactivate. The 4 T mode allows the user to push and release the switch to activate, then push and release the switch again to deactivate. An indicator  272  may light when the 2 T mode is selected, and an indicator  274  may light when the 4 T mode is selected. 
     An amperage input  252  may allow a user to select a desired output current. A wire feed speed input  254  may allow a user to select a desired wire feed speed of the wire  122 . The desired wire feed speed may be a desired steady-state wire feed speed. In some implementations, the inputs  252  and  254  may be combined into an adjustable knob. A user may press the adjustment knob to cycle between the inputs  252  and  254 , and then turn the adjustment knob to select a desired value of the current or wire feed speed. The selected desired value may be displayed on a display  250 , which may be a super bright red LED display. 
     A voltage input  262  may allow a user to select a desired output voltage of the welding signal. An inductance input  264  may allow a user to select a desired inductance which, for example, may optimize weld bead characteristics. An arc force input  266  may allow a user to select desired properties of arc force. A down slope input  268  may allow a user to select a down slope time, which is a function of the down ramp rate of the output current. In some implementations, the inputs  262 ,  264 ,  266 , and  268  may be combined into an adjustable knob. A user may press the adjustment knob to cycle between the inputs  262 ,  264 ,  266 , and  268 , and then turn the adjustment knob to select a desired value of the voltage, inductance, or down slope. The selected desired value may be displayed on a display  260 , which may be a super bright red LED display. 
     An advanced features input  280  may allow a user to select menus and toggle through various further inputs, which are displayed on the displays  250  and  260 . A MIG welding main menu may provide inputs for operation control, pre-flow, spot on/off, spot time, stitch on/off, stitch time, dwell time, run-in percentage, post-flow, burn back time, wire sharp, and/or a setup submenu. The setup submenu may provide inputs for wire feed units, amperage calibration, voltage calibration, wire speed calibration, arc hour display, VRD (on, off or triggered), total weld energy (for heat input computation), and/or factory defaults. A stick welding main menu may provide inputs for operation control, hot start on/off, hot start time, hot start amperage, and/or a setup submenu. The setup submenu may provide inputs for arc hour display, VRD disable, and factory defaults. The TIG main menu may provide inputs for operation control, pre-flow, post-flow, and a setup submenu. The setup submenu may provide inputs for arc hour display, VRD disable, and factory defaults. 
     Burn back time may refer to an adjustable period of time that the power supply  110  may provide power for the welding process after the wire feed stops in order to burn back the wire and prevent it from sticking in the weld puddle. Wire sharp refers to the application of predetermined current outputs applied to the wire, for example, a rapid series of powerful current pulses after the motor  166  is de-energized. This prevents a ball of molten metal from freezing on the end of the welding wire, and tapers the end of the weld wire to a sharp point, promoting a cleaner start when welding resumes. The current outputs terminate when an open-circuit is detected or after a predetermined time or condition is reached. Run-in percentage refers to a percent of wire feed speed. The percentage may range, for example, from about 25 percent to about 150 percent of the wire feed speed. The run-in setting may, for example, allow a user to temporarily alter the selected wire feed speed to optimize MIG weld start characteristics. 
     The control circuit  152  may receive each of the quantities respectively associated with each of the inputs. Further, although the above inputs are shown in particular implementations, each of the inputs may be configured as a dial, adjustment knob, button, or switch, for example. Additionally, in some implementations, some of the inputs may be automatically selected by the control circuit  152 . Which inputs are automatically selected and which inputs are user-selectable may depend on which welding process is selected. In some implementations, some parameters, for example wire diameter, material, gas, and joint design, may not be programmed into the control circuit  152 . 
     Now referring to  FIG. 3 , a method  300  for automatically selecting weld control algorithms is provided. The method  300  may be implemented in gas metal arc welding and flux core arc welding, for example when the MIG welding setting is selected. The method may also be implemented in shielded metal arc welding or tungsten inert gas welding, for example. The ordering of the steps presented herein is merely one implementation of the method  300 . Those skilled in the art will recognize that the ordering may be varied, that some steps may occur simultaneously, that some steps may be omitted, and that further steps may be added. Moreover, each step involving the controller may be implemented by configuring (e.g. programming) the controller to perform the step. 
     The method  300  starts in block  310 . In block  310 , if the selected welding process is gas metal arc welding or flux core arc welding, then the control circuit  152  may receive a magnitude of the output voltage from the voltage input  262 . In some implementations, the control circuit may also receive the wire feed speed, inductance, burn-back time, polarity (or variables that define a variable polarity, for example magnitude of polarity and frequency of change in polarity), and/or wire sharp settings from their respective inputs. If the selected welding process is shielded metal arc welding, the control circuit may receive output current, arc force, polarity (or variables that define a variable polarity, for example magnitude of polarity and frequency of change in polarity), hot start amplitude and/or hot start duration settings from their respective inputs. If the selected welding process is gas tungsten arc welding, the control circuit may receive output current, slope control (e.g. starting current, down slope time, and/or up slope time), crater fill, and/or polarity (or variables that define a variable polarity, for example magnitude of polarity and frequency of change in polarity) settings from their respective inputs. Any of the foregoing welding parameters can be user-selected, automatically-selected, or programmed. 
     In some implementations, regardless of the type of welding process, the control circuit  152  may instead receive feedback measurements of the actual magnitude of output voltage rather than a selected output voltage. The control circuit  152  may also receive feedback measurements of the actual magnitude of output current. The method  300  may proceed from block  310  to block  320 . 
     In decision block  320 , the control circuit  152  may continuously determine whether a selected welding parameter, for example the magnitude of the output voltage, is in a first range of values or a second range of values. If the magnitude of the output voltage is in a first range of values, then the method proceeds to block  330 . If the magnitude of the output voltage is in a second range of values, then the method proceeds to block  340 . In some implementations, if the selected welding process is, for example, gas metal arc welding or flux core arc welding, the determination of which block to proceed to may depend on whether the output voltage, inductance, wire feed speed, burn-back time, polarity (or variables that define a variable polarity, for example magnitude of polarity and frequency of change in polarity), wire sharp setting, or combinations thereof fall into respective first and second ranges of values. In other implementations, if the selected welding process is, for example, shielded metal arc welding, the determination of which block to proceed to may depend on whether the output current, arc force, polarity (or variables that define a variable polarity, for example magnitude of polarity and frequency of change in polarity), hot start amplitude and/or hot start duration, or combinations thereof fall into respective first and second ranges of values. If the selected welding process is, for example, gas tungsten arc welding, the determination of which block to proceed to may depend on whether the output current, slope control (e.g. starting current, down slope time, and/or up slope time), crater fill, and/or polarity (or variables that define a variable polarity, for example magnitude of polarity and frequency of change in polarity), or combinations therefore fall into respective first and second ranges of values. 
     In the implementations where the control circuit  152  receives feedback measurements of the actual magnitude of output voltage and/or output current instead of selected welding parameters, the determination of which block to go to may depend on whether the actual output voltage, actual output current, or combinations therefore, fall within the first or second ranges of voltages. The method  300  may proceed from block  320  to block  330 . 
     In block  330 , the control circuit  152  may select the first weld control algorithm. If the selected welding process is gas metal arc welding or flux core arc welding, the first weld control algorithm may be a proportional-integral-derivative (PID) feedback loop, for example, or one of several variations such as a proportional-integral (PI) control loop. The PI loop may be a fast inner loop that cycles about once every fifty microseconds, and may provide short-circuit, globular, and spray transfer. A fast loop may measure and store instantaneous current and voltage, maintain running averages, and use the instantaneous measurements to determine the desired characteristics for the subsequent fast loop cycle. While in the PI loop, the control circuit  152  may control the welding process (e.g. GMAW or FCAW) in voltage control mode, for example. That is, the first weld control algorithm may be a voltage control mode algorithm. 
     The PI loop may operate best in the first range of values. The first range of values may include two non-contiguous intervals: a first interval of between about 14 volts and about 17 or may specifically be between 14 volts and 17 volts, and a second interval of between about 20.3 volts and about 30 volts, or may specifically be between 20.3 volts and 30 volts. As such, the term “range” as defined herein may include two or more non-contiguous intervals. The method  300  may proceed from block  330  back to block  320  to re-determine whether the output voltage is still within the first range of values or is now within the second range of values. 
     If the selected welding process is shielded metal arc welding, the control circuit  152  may control the welding process in current control mode, for example. That is, the first weld control algorithm may be a current control mode algorithm. 
     In block  340 , the control circuit  152  may select the second weld control algorithm. If the selected welding process is gas metal arc welding or flux core arc welding, the second weld control algorithm may be a finite state machine (FSM) loop that governs multiple stages of the short-circuit transfer process. The second range of values may be set to between about 17 volts and about 20.3 volts, or may specifically be between 17 and 20.3 volts. Across this range, the FSM loop may best provide exceptional weld characteristics, including but not limited to spatter, base material penetration, bead shape and heat input, when operated in the short-circuit transfer mode. While in the FSM loop, the control circuit  152  may control the welding process (e.g. GMAW or FCAW) in current control mode or voltage control mode, for example. That is, the second weld control algorithm may be a voltage control mode algorithm or a current control mode algorithm. In some implementations, the control circuit  152  may control both current and voltage during the FSM loop, in which case the second weld control may a combination of a voltage and current control mode algorithm. If the selected welding process is shielded metal arc welding, the control circuit  152  may control the welding process in arc force mode, for example. That is, the second weld control algorithm may be an arc force control mode algorithm. The method  300  may proceed from block  340  back to block  320  to re-determine whether the output voltage is still within the second range of values or is now within the first range of values. 
     In blocks  330  and  340 , the selected ranges (e.g. voltage ranges) thus may provide optimal operation of each algorithm and the control circuit  152  may automatically transition between the algorithms based on changes in the welding parameter (e.g. output voltage) selected by the user or in the feedback measurements (e.g. of the actual output voltage). That is, the control circuit  152  may continuously monitor which of the ranges the welding parameters falls into, and change control algorithms accordingly. Additionally, in blocks  330  and  340 , the power supply  110  generates welding power based respectively on the first and second algorithms. 
     Actual characteristics of the welding power  116 , such as the actual output voltage, may be correlated to the user-selected parameters, such as the output voltage. Thus, a user-selected parameter will correspond to the actual output characteristics of the welding power  116 . Thus, the welding algorithms, for example the PI and FSM loops, may be normalized to ensure a seamless transitions at voltage bounds, for example 17 volts and 20.3 volts. 
     In some implementations the control circuit  152  may provide three, four, five, or any number of different automatically selected weld control algorithms based on whether the inputs, feedback, or any combinations thereof, fall into three, four, five, or any number of a plurality of ranges. 
     In some implementations, selection of welding parameters or detection of feedback in any of the welding processes discussed above may cause selection of alternate circuit paths that effectively implement weld control algorithms. For example, in gas metal arc welding, when the output voltage is in a first range, the system may switch to a first circuit path that effectively implements the PI loop, and when the output voltage is in a second range, the system may switch to a first circuit path that effectively implements the FSM loop. 
     In some implementations the first or second algorithm may be a controlled dip transfer algorithm. Controlled dip transfer may refer to a cyclical control sequence that regulates power supplies, wire feed motors or shielding gas valves to enhance GMAW short circuit transfer performance. By monitoring instantaneous voltage, current, power, energy, heat or other weld conditions and rapidly varying control techniques, parameters and feedback in response, critical characteristics like penetration, bead shape, or spatter can be balanced or optimized. Controlled dip transfer may be implemented in software or electronics as a finite state machine or other mechanism that selects distinct, specialized control modes or circuits for each identified phase of a the short circuit transfer (also called dip transfer) process. 
     Any of the controllers, control circuits, modules, servers, or engines described may be implemented in one or more computer systems or integrated controllers. One exemplary system is provided in  FIG. 4 . The computer system  1000  includes a processor  1010  for executing instructions such as those described in the methods discussed above. The instructions may be stored in a computer readable medium such as memory  1012  or storage devices  1014 , for example a disk drive, CD, or DVD, or in some form of nonvolatile memory, internal or external to the processor, such as EPROM or flash. The computer may include a display controller  1016  responsive to instructions to generate a textual or graphical display on a display device  1018 , for example a computer monitor. In addition, the processor  1010  may communicate with a network controller  1020  to communicate data or instructions to other systems, for example other general computer systems. The network controller  1020  may communicate over Ethernet or other known protocols to distribute processing or provide remote access to information over a variety of network topologies, including local area networks, wide area networks, the Internet, or other commonly used network topologies. 
     In other embodiments, dedicated hardware implementations, such as application specific integrated circuits, programmable logic arrays and other hardware devices, can be constructed to implement one or more of the methods described herein. Applications that may include the apparatus and systems of various embodiments can broadly include a variety of electronic and computer systems. One or more embodiments described herein may implement functions using two or more specific interconnected hardware modules or devices with related control and data signals that can be communicated between and through the modules, or as portions of an application-specific integrated circuit. Accordingly, the present system encompasses software, firmware, and hardware implementations. 
     In accordance with various embodiments of the present disclosure, the methods described herein may be implemented by software programs executable by a computer system or processor. Further, in an exemplary, non-limited embodiment, implementations can include distributed processing, component/object distributed processing, and parallel processing. Alternatively, virtual computer system processing can be constructed to implement one or more of the methods or functionality as described herein. 
     Further, the methods described herein may be embodied in a computer-readable medium. The term “computer-readable medium” includes a single medium or multiple media, such as a centralized or distributed database, and/or associated caches and servers that store one or more sets of instructions. The term “computer-readable medium” shall also include any medium that is capable of storing, encoding or carrying a set of instructions for execution by a processor or that cause a computer system to perform any one or more of the methods or operations disclosed herein. 
     As a person skilled in the art will readily appreciate, the above description is meant as an illustration of the principles of this invention. This description is not intended to limit the scope or application of this invention in that the invention is susceptible to modification, variation and change, without departing from spirit of this invention, as defined in the following claims.