Adaptive control of a laser brazing / welding process with a robot

Abstract

Method for adaptive control of an automated work process by a robot, comprising the following steps: Providing a software program for generating process signals that can be executed by the robot during the automatic operation, including one or more execution commands; Providing a first signal-value channel for at least one control process parameter (20) of the robot, wherein the at least one control process parameter (20) is assigned to a controlled device, wherein the first signal-value channel is subject to a first waiting time (t1); Synchronizing the execution timing of the first signal-value channel with the one or more execution commands by taking into account the first waiting time (t1) in relation to the one or more execution commands; and Execution of the software program to generate the process signals and sending the process signals to the controlled device to implement the synchronized execution timing control of the controlled device in relation to the instructed movement of the robot.

Description

[0001] This application claims the benefit of U.S. Provisional Patent Application Serial No. 61 / 806,433, filed March 29, 2013, and also claims the benefit of U.S. Provisional Patent Application Serial No. 61 / 808,328, filed April 4, 2013.

[0002] This invention relates to robot controllers, and more particularly, the invention is directed to adaptive control of a robotic laser brazing / welding process.

[0003] Robotic laser brazing / laser welding has become increasingly popular in the automotive manufacturing industry due to its precision, low thermal distortion, and cost-effectiveness. Many automotive original equipment manufacturers (OEMs) have begun using robotic laser brazing / laser welding for the production of car roofs and trunk lids, especially for welding aluminum.

[0004] Commonly used robotic laser brazing / welding tools use a software program to generate process signals such as wire feed speed and wire feed start commands to a wire feeder, and process signals such as laser power and laser irradiation commands to a laser beam generator. All of these signals are controlled via an arc start command and an arc end command. Current software lacks adequate signal timing adjustment capabilities to meet the laser brazing / welding process requirements. The process is suboptimal because process parameters such as wire feed speed and laser power are always based on commanded values ​​set during the welding sequence and are not adaptable to the actual tool speed, which is typically measured at the tool center point (TCP).As a non-limiting example, it is difficult to time the timing between laser power and wire feed speed during changes in laser power when the wire feed speed is based on commanded values.

[0005] Therefore, robotic applications for laser brazing / welding require flexible and precise synchronization of the timing control for various third-party device and process parameters, such as laser power, gas flow, wire temperature, and wire feed speed. Acceptable laser brazing / welding performance also requires adaptive control of process parameters. In particular, acceptable laser brazing / welding performance requires that process parameters be controlled independently of each other with respect to the actual welding speed.

[0006] For example, during a corner move, the actual movement speed of the welding tool at a corner area may be significantly lower than the commanded speed. Similarly, the welding tool is subject to acceleration or deceleration at the beginning and end of its movement, as well as during changes in direction and speed, causing the actual movement speed of the robot welding tool to change. To compensate for this, the welding parameters must be dynamically updated based on the actual welding speed to ensure the quality of a laser weld. During acceleration or deceleration of the robot welding tool, it is desirable to provide independent edge control for process parameters based on the actual acceleration or deceleration of the robot at the start or end of the laser brazing / welding process.The ability to adapt brazing / welding process parameters to welding speed is critical in laser applications where the laser can quickly cut a hole in the material being welded or feed more wire than needed. Without this adaptability, developing, programming, and validating welding sequences is tedious, time-consuming, and difficult.

[0007] Such control systems and control methods are known from DE 10 2006 021 065 A1, EP 1 757 410 B1, US 2013 / 0 200 053 A1; US ​​2003 / 0 033 052 A1; JP 2005-279 687 A1 and JP H03-114 669 A.

[0008] It is an object of the invention to provide a system and method for laser brazing / welding in which process parameters are controlled independently of one another with respect to the actual welding speed. Another object of the invention is to provide a system and method for laser brazing / welding in which process parameters are adaptable to the actual speed of the tool center point.

[0009] In accordance with the present disclosure, a system and method for laser brazing / welding has surprisingly been discovered in which process parameters are controlled independently of each other with respect to the actual welding speed, and in which process parameters are adaptable to the actual speed of the tool center point.

[0010] In one embodiment, a method for adaptively controlling an automatic operation by a robot is provided. A software program is provided to generate process signals executable by the robot during the automatic operation, including one or more execution instructions. A first signal-value channel is provided for at least one control process parameter of the robot, wherein the first signal-value channel is subject to a first wait time. The timing of the execution of the first signal-value channel is coordinated with the one or more execution instructions by taking into account the first wait time relative to the one or more execution instructions. The software program is executed to generate the process signals, wherein the robot is operated in response to the synchronized timing of the execution of the execution instructions.

[0011] In one embodiment, the timing of the execution of the first signal-value channel is delayed upon receipt of the one or more execution instructions by the amount of the first wait time.

[0012] In another embodiment, a first signal-on channel is provided for the at least one control process parameter, wherein the first signal-on channel is subject to a second wait time. The timing of the execution of the first signal-on channel is synchronized with the one or more execution instructions by taking the second wait time into account in relation to the one or more execution instructions.

[0013] In a further embodiment, a software program is provided for generating process signals executable during the robot's automatic operation, which process signals include one or more execution commands defined in a welding sequence. A first signal-value channel is provided to control at least one process parameter for laser brazing / welding of the robot, wherein the first signal-value channel is subject to a first wait time relative to the one or more execution commands. The timing of the execution of the first signal-value channel is synchronized with the one or more execution commands by adjusting the timing of the execution of the first signal-value channel relative to the one or more execution commands by the size of the first wait time.The software program is executed to generate the process signals, wherein the robot is operated in response to the synchronized timing of the execution of the execution commands. An actual speed of the laser brazing / welding operation by the robot can be tracked, providing independent and adaptive control of the first signal value channel relative to the speed of the laser brazing / welding operation. The at least one laser brazing / welding process parameter is one of laser power, laser on / off, wire feed speed, wire feed on / off, dual wire feed speed, dual wire feed on / off, gas flow, gas flow on / off, gas velocity, gas pressure, gas temperature, wire temperature, wire preheat, and wire preheat on / off.

[0014] Also disclosed is an apparatus for adaptively controlling a robotic laser brazing / welding process. The apparatus includes a robot controller, a robot arm carrying a brazing / welding tool connected to the controller, and a non-volatile memory element connected to the controller and storing a software program executed by the controller to coordinate movement of the robot. The software program generates process signals executable during the automated operation, comprising one or more execution commands specified in a welding sequence. A first signal-value channel controls at least one process parameter of the laser brazing / welding process. The first signal-value channel is subject to a first wait time relative to the one or more execution commands.The software program synchronizes the timing of the execution of the first signal-value channel with the one or more execution instructions by adjusting the timing of the execution of the first signal-value channel relative to the one or more execution instructions by the size of the first wait time.

[0015] The above-mentioned and other advantages of the present invention will be readily apparent to those skilled in the art from the following detailed description of a preferred embodiment when considered in light of the accompanying drawings in which: Fig. Figure 1 is a schematic block diagram of an apparatus for performing adaptive control of a robotic laser brazing / welding operation according to the invention; Fig. Figure 2 illustrates the time relationships between process parameters during a laser brazing / welding process according to the invention; Fig. Figure 3 illustrates a general ramp-up process in conjunction with the time relationships between process parameters during a laser brazing / welding process according to the invention; and Fig. 4 illustrates the increase process of Fig. 3 in connection with the time relationships between two exemplary process parameters, each with two control channels, during a laser brazing / welding process according to the invention.

[0016] The following detailed description and accompanying drawings describe and illustrate various exemplary embodiments of the invention. The description and drawings are intended to enable one skilled in the art to make and use the invention and are not intended to limit the scope of the invention in any way. With respect to the disclosed methods, the steps depicted are exemplary in nature, and thus the order of the steps is not required or critical.

[0017] As in Fig. 1, an apparatus for performing adaptive control of an automated laser brazing / welding operation includes a robot controller 10 that controls the movement of a robot arm 12 carrying the brazing / welding tools. The controller 10 also controls process parameters 20 that affect the brazing / welding process. As non-limiting examples, these process parameters 18 may include the wire feed speed of a wire feeder 14 and the power level of a laser power supply 16. A software program for coordinating the robot movement, wire feed speed, and laser power is stored in a non-volatile memory element 18 connected to the controller 10.

[0018] The present invention recognizes and takes into account the fact that each of the process parameters 20 in Fig. 1 is subject to a waiting time between a time at which a process command is first given and a time at which the process command begins to be executed. Furthermore, each of the process parameters 20 is typically subject to a different waiting time than any of the other process parameters.

[0019] Exemplary relationships between the timing of these process parameters 20 are generally described with reference to Fig. 2 to Fig. 4. The exemplary time relationships between process parameters of Fig. 2 to 4 are illustrated in particular with reference to an arc starting time 30, an arc starting time 32, an arc stopping time 34, and an arc stopping time 36 for both the FINE motion type and the CNT100 (corner) motion type in the laser brazing / welding process. Each of the horizontal time axes of Fig. Figures 2 through 4 illustrate process timing pulses, where a control pulse or command is initiated or modified by the software control program to effect a response to a process parameter such as part motion, robot motion, wire feed, wire speed, laser on, laser power level, and the like. It will be appreciated that the control pulse or command can be a commonly used control scheme, digital or analog.

[0020] Fig. Figure 2 shows a general process signal timing sequence for a CNT100 (corner) motion type between arc starting and arc ending. Each channel has similar control capability, with each channel considering only specific wait times associated with the process parameter controlled by that channel. The brazing / welding corner speed of time axis 40 represents the desired constant welding speed through the brazing / welding corner pass. However, motion line 50 shows the speed of the tool relative to the line required to maintain the brazing / welding corner speed of time axis 40 constant. In particular, a welding motion start command 52 is provided so that the line motion begins concurrently with the arc started time 32.A separate welding movement stop command 54 is provided to signal the end of a commanded movement on the movement line 50 before the arc termination time 36.

[0021] In order to guarantee that the arc-started time 32 coincides with the welding movement start command 52, the present invention takes into account a waiting time t1 between the arc-starting time 30 and the arc-started time 32. Thus, the arc-started time 32 is defined as the arc-starting time 30 plus the waiting time t1. In other words, the time axis 60 must be Fig. The arc start signal shown in Figure 2 must be commanded before the expected arc start time 32 by the magnitude of the wait time t1. Similarly, the arc end signal shown in the time axis 70 must be commanded before the arc end time 36 by a magnitude of the wait time t7. It will be understood that the wait time t1 may or may not be equal to the wait time t7. It will also be understood that the wait time t1 may be independent of the wait time t7, which is because the arc start signal 60 is controlled by a separate channel, different from the arc end signal 70.

[0022] For each process control parameter A used in the brazing / welding process, both a signal value channel, shown as time axis 80, and a signal-on channel, shown as time axis 90, are provided because each process control parameter is associated with its own signal value, and because each process or control associated with the brazing / welding operation is subject to an independent and known wait time associated with that process parameter. It will be appreciated that the signal-on channel can control the movement of a portion of the laser brazing / welding process, such as movement of the robot arm, or also the activation and / or deactivation of a portion of the laser brazing / welding process, such as the activation and / or deactivation of the laser.For example, a process control parameter associated with the laser requires a signal value channel to control a process parameter associated with the laser, such as a laser power level, and also requires a signal-on channel to indicate when the laser is on or off. In addition, there is a known wait time t2 for the process control parameter A, which represents the delay time of the signal value and the realization of the signal value before the arc-start time 32. For example, the signal value of the process control parameter may call for a laser power of 50% when the laser turns on, but this power setting must be commanded before the laser actually turns on. Thus, the control system of the present invention adjusts the wait time t2 relative to the arc-start wait time t1 to achieve a desired signal value 80 before the arc-start time 32.

[0023] When any change is made to the process parameter signal value, there is also a known waiting time t5, which represents the delay time of the signal value change before the actual change to the signal value. Thus, the signal value change is required on the time axis 80 at the arc termination time 34, as shown in Fig. 2, but does not operate until a time t5 after the arc termination time 34. Consequently, the control channel 80 takes into account the waiting time t5 associated with the change in the signal value of the process parameter in relation to the waiting time t7 in order to achieve a desired signal value 80 before the arc termination time 36. As shown in Fig. 2, the arc termination signal of time axis 70 is provided at a time t7 prior to the arc termination time 36, which also coincides with a time t4 prior to a motion signal termination signal on time axis 50. The arc termination signal is also established at a time t5 prior to the signal value change relative to the arc termination time 36.

[0024] Similarly, the present invention incorporates an independent wait time t3 between the arc start signal 30 and the time at which the signal-on channel signal turns on in the time axis 90 to ensure that the signal-on channel turns on precisely at the arc-started time 32. Thus, the present invention allows the control system to adjust the signal-on wait time t3 relative to the arc-start wait time t1 to synchronize the signal-on channel at signal with the arc-started time 32. Similarly, the present invention incorporates the signal-on channel wait time t6 relative to the arc-end signal wait time t7 to ensure that the signal-on channel 90 turns off precisely at the arc-ended time 36.

[0025] Importantly, each control channel independently considers each delay time associated with that control channel. This is necessary because each of the delay times t2, t3, t5, and t6 is independent of each other, even between the signal-value channel and the signal-on channel controlling the same device. Furthermore, each control channel is capable of providing its own on- and off-control parameters. This allows each process parameter associated with the brazing / welding operation to be precisely controlled. The present invention provides a precise signal timing adjustment capability that optimizes the precision and utility of the laser brazing / welding process by synchronizing the timing between all process parameters during the laser brazing / welding process.

[0026] In an additional embodiment of the present invention, each of the control channels is also capable of adapting the control signal to the current speed of the brazing / welding process. As a non-limiting example, the speed of the laser brazing / welding operation and a position of tools performing the brazing / welding operation can be measured relative to a tool center point (TCP) designated by known methods, or can be measured by other known methods with reference to a known point on the tool or on the part undergoing the laser brazing / welding process. As stated above, particularly with regard to a start / stop movement of the tool and its directional changes, the tool is subject to acceleration forces that vary with the speed of the tool.For example, the actual movement speed of the welding tool in a corner area may be significantly lower than the commanded speed.

[0027] The present invention compensates for changes in tool speed as well as changes in any process parameter by allowing independent and adaptive control of any process parameter during the laser brazing / welding process. Fig. 3 defines a general process signal timing in a variable speed FINE motion type between an arc start time 30 and an arc end time 36.

[0028] Everyone in Fig. The channel shown in Figure 3 indicates a similar control capability, with each channel also considering only specific wait times associated with the process parameter controlled by that channel. The TCP brazing / welding speed of timeline 140 shows a desired, variable welding speed through a tool movement adjustment shown in timeline 150. Timeline 160 controls a signal start channel, and timeline 170 controls a signal end channel associated with the signal start channel of timeline 160.

[0029] In Fig. 3, the welding motion line receives an "off" signal 152 at arc-start time 32. Instead of stopping abruptly, which may be physically impossible, the TCP speed adjusts to the motion characteristics of the tool, adaptively decreasing the TCP speed at point 142 to ensure that the TCP speed is zero concurrently with the motion stop signal 152. The motion channel sends an "on" signal at 154, which is also adjusted by an adaptive increase in TCP speed at 144. Subsequently, the motion channel 150 receives an "off" signal 156 at arc-stop time 34, which is adjusted by an adaptive decrease 146 in TCP speed. The motion channel 150 additionally receives an "on" signal at 158 ​​that coincides with the arc termination time 36, which is adjusted by an adaptive increase 148 of the TCP speed.

[0030] Likewise, the signal value signal shown by time axis 180 provides an adaptive increase in signal value to match the TCP speed time axis 140. Specifically, the signal value signal slowly increases over an extended period of time at point 182 to match the signal value parameter to the increase in TCP speed at 144. Subsequently, the signal value signal slowly and adaptively decreases at 184 to match the signal value parameter to the decrease in TCP speed at 146. Thus, the present invention enables a user to adaptively control process parameters associated with the laser brazing / welding process.

[0031] Variable, adaptive control algorithms can be used to control the rate and speed of changes to process parameter values. The present invention allows the use of any adaptive control algorithm. As a non-limiting example, an exemplary adaptive control algorithm useful in the present invention is provided below as Equation 1. speed_ratio=act_speed / cmd_speed where 0 speed_ratio 1,lpw=cmd_lpw(1−k1∗(1−speed_ratio)), where 0 k1 1 and lpwmin lpwcmd_lpwwfs=cmd_wfs(1−k2∗(1−speed_ratio)),where 0 k1 1 and wfsmin wfs cmd_wfsist.

[0032] Equation 1 describes a simple proportional, adaptive control algorithm in which (a) cmd_speed is the command welding speed specified in the welding sequence; (b) act_speed is the measured welding speed; (c) speed_ratio is limited to less than 1.0 (d) cmd_lpw is the command welding speed specified in the welding sequence; (e) lpw is the set laser power; (f) wfs is the set wire feed speed; (g) k1 and k2 are the control gains for lpw and wfs, respectively; (h) lpwmin is the user-defined lower limit for the set laser power; and (i) wfsmin is the user-defined lower limit for the set wire feed rate.

[0033] When a control gain is zero or an actual weld speed equals a commanded weld speed, there is no adjustment to the command process parameters when using the algorithm of Equation 1. If an actual weld speed is less than a commanded weld speed, the process parameters are reduced proportionally, using the gain to control the reduction rate. The control granularity of any adaptive control algorithm can be set to any interpolated loop time or to a multiple of interpolated loop times. It is also possible to apply the updated frequency to some or all of the control channels simultaneously.

[0034] Other adaptive control methods are also available. In one embodiment of the invention, a user of the present invention is provided with four different adaptive control methods that allow adaptive control of process parameters to adapt them to acceleration and deceleration of a motion during arc starting, arc stopping, or sequence changes during a laser brazing / welding operation. A first adaptive control method does not apply time-linear incrementation to the control during either tool acceleration or deceleration. In the first adaptive control method, the signal value will start at a commanded value and will maintain that value by accelerating the laser brazing / welding tool, or will maintain a current value by decelerating the tool, or both.This first adaptive control scheme is known as the time-linear zero-slope control scheme.

[0035] A second adaptive control method utilizes a known acceleration or deceleration time of the movement of a piece of laser brazing / welding equipment and provides for automatic, time-linear incrementing of a signal value during the known acceleration or deceleration time of the movement. In the second adaptive control method, a signal value will start at a first value and increase linearly to a commanded value during the known acceleration time of the movement, or will start at a current value and decrease linearly to a user-defined ramp value during the known deceleration time of the movement, or both. Thus, the ramp rate will be relatively higher for shorter acceleration or deceleration times, while the ramp rate will be relatively lower for longer acceleration or deceleration times.With this adaptive control method, it is not necessary for a user to know the actual acceleration and deceleration times of the movement. Instead, the present invention allows for the adaptive control to automatically ramp up during the acceleration times at arc start or during the deceleration times at arc end. This second adaptive control method is known as the automatic ramp up control method.

[0036] A third adaptive control method allows a user to specify an adaptive control time value to be implemented in synchronization with the motion start timing. In the third adaptive control method, a signal value will start at a first value and linearly increase to a user-defined slope end value during the user-defined adaptive control time upon acceleration of a piece of laser brazing / welding equipment, or will start at a current value and linearly decrease to a commanded value during the user-defined adaptive control time upon deceleration of the equipment, or both. Consequently, the slope will be relatively higher for shorter, user-selected acceleration and deceleration times, and the slope will be relatively lower for longer, user-selected acceleration times.The linear ramp will begin in synchronization with the motion start timing, allowing the linear ramp to occur after a tool movement has begun. This third adaptive control method is known by users as a time-linear ramp control method.

[0037] A fourth adaptive control method utilizes the acceleration and deceleration times of a movement of a piece of laser brazing / laser welding equipment and incorporates an automatic, linear rise of a signal value during the known acceleration and deceleration times of the movement in synchronization with a movement start timer. The rise time is the acceleration time of the movement at arc start or the deceleration time of the movement at arc end. Consequently, the edge start timer is synchronized with the movement start timer at arc start or with a movement end timer at arc end.In this fourth adaptive control method, a signal value will start at a fixed initial value and ramp up linearly to a commanded value during the known acceleration time of the move, or ramp down linearly from a current value to the specified final value at arc termination, or both, in accordance with the velocity profile of the actual movement during acceleration and deceleration. Because the ramp up is based on actual acceleration times, it can be nonlinear. The ramp up can start in synchronization with the move start timing or with the move stop timing, allowing the ramp up to occur after a tool movement has started or stopped as needed. This fourth adaptive control method is known as a ramp-up control method.

[0038] The process signal time sequence of Fig. 3 also synchronizes the timing between all process parameters during the laser brazing / welding process. To ensure that the arc-started time 32 coincides with the weld start motion command 52, the present invention considers a waiting time t'1 between the arc-starting time 30 and the arc-started time 32. Consequently, the arc-started time 32 is defined as the arc-starting time 30 plus the waiting time t'1. In other words, the time axis 160 of Fig. The arc start signal shown in Figure 3 must be commanded before the expected arc start time 32 by the magnitude of the wait time t'1. Likewise, the arc end signal shown in the time axis 170 must be commanded before the arc end time 36 by a magnitude of the wait time t'1. It will be understood that the wait time t'1 may or may not be equal to the wait time t'7. It will also be understood that the wait time t'1 may be independent of the wait time t'7, which is because the arc start signal 160 is controlled by a separate channel, different from the arc end signal 170.

[0039] For each process control parameter A defined in the Fig. 3, both a signal-value channel, shown as time axis 180, and a signal-on channel, shown as time axis 190, are provided because each process control parameter is associated with its own signal value, and because each process or control associated with the brazing / welding process is subject to an independent and known wait time associated with that process parameter. For example, the process control parameter associated with a laser requires a signal-value channel to control a process parameter associated with the laser, such as a laser power level, and also requires a signal-on channel to indicate when the laser is turned on or off. In addition, a known wait time t'2 exists for process control parameter A, which represents the delay time of the signal value and the realization of the signal value before the arc-start time 32.For example, the process control parameter Signal Value Channel may require a laser power of 50% when the laser is on, but this power setting must be commanded before the laser is actually on. Thus, the control system according to the present invention adjusts the wait time t'2 relative to the arc start wait time t'1 to achieve a desired signal value 180 before the arc start time 32.

[0040] When any change is made to the signal value of the process parameter, there is also a known waiting time t'5, which represents the delay time of the signal value change before the actual change to the signal value. Thus, as in Fig. 3, the signal value change on the time axis 180 is requested at the arc termination time 34, which, however, has no influence until a time t'5 after the arc termination time 34. Consequently, the control channel 180 takes into account the waiting time t'5 associated with the change in the signal value of the process parameter in relation to the waiting time t'7 in order to achieve a desired signal value 180 before the arc termination time 36. As shown in Fig. 3, the arc termination signal is provided to time axis 170 at a time t'7 before the arc termination time 36, which also coincides with a time t'4 before a termination signal of the moving line signal on time axis 150. The arc termination signal is also formed a time t'5 before the change in signal value relative to the arc termination time 36.

[0041] Similarly, the present invention considers an independent wait time t'3 existing between the arc start signal 30 and the time at which the signal-on channel signal turns on on the time axis 190 to ensure that the signal-on channel turns on precisely at the arc-started time 32. Thus, the present invention allows the control system to adjust the signal-on wait time t'3 relative to the arc length start wait time t'1 to synchronize the signal-on channel at signal with the arc-started time 32. Similarly, the present invention considers the signal-on channel wait time t'6 relative to the arc-end signal wait time t'7 to ensure that the signal-on channel 190 turns off precisely at the arc-ended time 36.

[0042] In another embodiment, a user is provided with a user-selectable time delay that allows the user to manually adjust the control system by adding the user-selectable time delay to an arbitrary wait time associated with a control channel. This user-selectable time delay provides a user with the ability to manually fine-tune and adjust a control of the delay time of the controller's adaptive ramp relative to the commanded motion start time. The user-selectable time delay is intended to allow the user to address tolerance coverage issues within the laser brazing / welding robotic process.As a non-limiting example, the user-selectable time delay may be used to account for a mechanical delay in the actual motion start time relative to the commanded motion start time caused by gear meshing backlash.

[0043] Importantly, each control channel independently considers any arbitrary wait time associated with that control channel, which is necessary because each of the wait times t'2, t'3, t'5, and t'6 are independent of each other. Thus, the present invention provides the ability to precisely adjust the signal timing through the signal value channel, optimizing the accuracy and usability of the laser brazing / welding process by synchronizing the timing between all process parameters during the laser brazing / welding operation. Furthermore, each control channel is capable of providing its own on / off control parameters through the signal on channel by incorporating the use of adaptive process parameter control. Thus, each process parameter associated with the brazing / welding operation can be precisely controlled in addition to the process parameter timing.In one embodiment, the present invention therefore enables adaptive controls of process parameters associated with the laser brazing / welding operation as a function of the arc start time 30 and the arc stop time 36.

[0044] Fig. Figure 4 provides an example sequence of process signal timing for a laser brazing / welding process for two process parameters in the FINE motion type at the arc start time 30 and the arc end time 36. In a laser brazing / welding process of the type shown in Fig. 4, the welding parameters must be dynamically updated based on the actual welding speed to ensure the quality of the laser weld. During acceleration of the robot welding tool, it is desirable to provide independent edge rise control for process parameters based on actual robot acceleration or deceleration at the start or end of the laser brazing / welding process. The ability to adapt the brazing / welding process parameters to the welding speed is critical in laser applications where the laser can quickly cut a hole in the material being welded or feed more wire than needed. Without this adaptability, developing, programming, and validating welding sequences is tedious, time-consuming, and difficult.

[0045] As mentioned above, each channel of Fig. 4 an independent controller, each channel has similar control capability and furthermore, each channel only considers specific wait times associated with the process parameter controlled by that channel. The brazing / welding speed of time axis 240 shows a desired variable welding speed by adjusting the tool movement, which is shown in time axis 250. Each additional control channel considers dynamic control of a process parameter relative to the welding speed time axis 240. The arc start signal is shown in time axis 260 and the arc end signal in time axis 270. Control of the signal-value parameter of the laser power is shown in time axis 280 and control of a signal-value parameter of the wire feed speed is shown in time axis 310.A control of a signal-on parameter is shown in the time axis 290 and a control of a signal-on parameter of the wire feed is shown in the time axis 320.

[0046] The arc start time axis begins with an arc start signal 262, which is the basis of the timing for all related to each of the Fig. 4 in relation to the arc started time 32. The arc end time axis controls the end of the laser brazing / laser welding operation by triggering the arc end time 34 with an arc end signal at 272, which forms the basis of the timing for all actions related to each of the process parameters in Fig. 4 actions in relation to the arc termination time 36.

[0047] Thus, the welding motion line receives an "off" signal 252 that coincides with a first taught position of the robot at time 300, represented as (arc start time 30 plus T1), where T1 is the motion control wait time. Instead of stopping abruptly, which may be physically impossible, the welding speed advances and adapts to the motion characteristics of the tool, adaptively reducing the welding speed at 242 to ensure that the welding speed is zero simultaneously with the motion stop signal 252 at (arc start time 30 plus T1), the in-position time 300. At the same time, the laser power signal value parameter and the wire feed speed signal value parameter are both controlled as a function of the arc start time 30.Specifically, the laser power level at 282 is set at (arc starting 30 plus T3), where T3 is the laser power control wait time. Similarly, the wire feed control speed is set at 312 at (arc starting 30 plus T4), where T4 is the wire feed speed control wait time. The laser on (signal on) parameter receives an "on" signal at (arc starting 30 plus T5), where T5 is the laser wait time. Similarly, the wire feed speed on (signal on) parameter receives an on signal at (arc starting 30 plus T6), where T6 is the wire feeder wait time. Time T7 accounts for any latency associated with laser device movement after receiving the on signal. In this way, all waiting times associated with any of the process parameters related to the laser brazing / welding process are taken into account in relation to the arc starting time 30.The control of each of the parameters is therefore possible independently and at an extremely high level of accuracy.

[0048] At arc-started time 32, the motion channel sends an "on" signal at 254 that coincides with the arc-started time 32, which is also adjusted by an adaptive increase in welding speed at 244, in laser power at 284, and in wire feed speed at 314. Subsequently, the motion channel 25 receives an "off" signal 256 that coincides with a taught position reached by the robot at time 302, defined as (arc-stop + T2), where T2 is the motion "off" control wait time. The "off" signal 256 is preempted by an adaptive reduction 246 of the welding speed, laser power 286, and wire feed speed 316 to ensure that the process parameters change adaptively when the welding speed decreases to zero simultaneously with the move stop signal 256 at (arc termination 34 + T2), the in-position time 302.The laser power control receives an "off" signal at a time (arc termination 34 + T8), where T8 is the wait time of the laser power control parameter. The wire feed speed control receives an "off" signal at a time (arc termination 34 + T11), where T11 is the wait time of the wire feed speed control parameter. Likewise, the laser on control parameter receives an off signal at a desired time (arc termination 34 + T9), where T9 is the wait time of the laser on control parameter, and the wire feed speed on control parameter receives an off signal at a desired time (arc termination 34 + T10), where T10 is the wait time of the wire feed speed on control.Finally, the motion channel 250 additionally receives an "on" signal at 258 coinciding with the arc termination time 36, which is adjusted by an adaptive increase 248 in the welding speed as the tool repositions.

[0049] Each of the process parameters of Fig.4 is therefore easily controlled with respect to any waiting times for each process parameter, which further allows for dynamic adjustment of other process parameters associated with the laser brazing / welding process with respect to any changes in the actual welding speed, including any changes in welding speed due to tool acceleration or deceleration. It will be appreciated that the illustrated timing and adaptive controls of the process can be extended to any additional channels associated with an additional process parameter, such as twin wire feed, gas flow and speed, wire temperature / preheat, and the like. The present invention therefore maximizes welding speed and minimizes the difficulty of developing, programming, and validating welding sequences for each part to be joined by a laser brazing / welding process.

Claims

[1] A method for the adaptive control of an automatic work process by a robot, comprising the steps: Providing a software program for generating process signals executable by the robot during the automatic work process, including one or more execution commands; Providing a first signal-value channel for at least one control process parameter (20) of the robot, wherein the at least one control process parameter (20) is associated with a controlled device, wherein the first signal-value channel is subject to a first waiting time (t1); Synchronizing the execution timing of the first signal-value channel with the one or more execution instructions by taking into account the first waiting time (t1) relative to the one or more execution instructions; and Executing the software program to generate the process signals and sending the process signals to the controlled device to implement the synchronized execution timing of the controlled device relative to the commanded movement of the robot. [2] The method of claim 1, wherein during the step of synchronizing the first signal-value channel, the execution timing of the first signal-value channel is delayed by the amount of the first wait time (t1) upon receipt of the one or more execution instructions. [3] The method of claim 1, further comprising the steps of: Providing a first signal-on channel (90) for the at least one control process parameter (20), wherein the first signal-on channel (90) is subject to a second waiting time (t2); and Synchronizing the execution timing of the first signal-on channel (90) with the one or more execution instructions by taking into account the second wait time (t2) relative to the one or more execution instructions. [4] The method of claim 3, wherein during the step of synchronizing the first signal-on channel (90), the execution timing of the first signal-on channel (90) is delayed by the size of the second wait time (t2) upon receipt of the one or more execution commands. [5] The method of claim 4, further comprising the steps of: Providing independent and adaptive control of one of the first signal-value channel and the first signal-on channel (90) in relation to a speed of the automatic operation. [6] A method for adaptively controlling an automatic laser brazing / welding process by a robot, comprising the steps of: Providing a software program for generating process signals executable by the robot during the automatic work process, including one or more execution commands defined in a welding sequence; Providing a first signal-value channel for controlling at least one Process parameters (20) of the laser brazing / welding of the robot, wherein the at least one brazing / welding process parameter (20) is associated with a controlled device, wherein the first signal value channel is subject to a first waiting time (t1) relative to the one or more execution commands; Synchronizing an execution timing of the first signal-value channel with the one or more execution instructions by adjusting the execution timing of the first signal-value channel relative to the one or more execution instructions by the size of the first waiting time (t1); and Executing the software program to generate the process signals and send the process signals to the controlled device to implement the synchronized execution timing of the controlled device relative to the commanded movement of the robot. [7] The method of claim 6, further comprising the step of: Tracking an actual speed of the laser brazing / welding process; and Providing independent and adaptive control of the first signal value channel relative to the speed of the laser brazing / welding process. [8] The method of claim 6, wherein the at least one process parameter (20) of the laser brazing / welding is one of laser power, laser on / off, wire feed speed, wire feed on / off, double wire feed speed, double wire feed on / off, gas flow, gas flow on / off, gas velocity, gas pressure, gas temperature, wire temperature, wire preheating, and wire preheating on / off. [9] The method of claim 6, wherein the step of synchronizing the execution timing of the first signal value channel is automatically updated in response to a change in the welding sequence. [10] The method of claim 6, further comprising the steps of: Providing a first signal-on channel (90) for controlling at least one Process parameter (20) of laser brazing / welding, wherein the first signal-on channel (90) is subject to a second waiting time (t2) relative to the one or more execution commands; and Synchronizing an execution timing of the first signal-on channel (90) with the one or more execution instructions by adjusting the execution timing of the first signal-on channel (90) relative to the one or more execution instructions by the size of the second wait time (t2). [11] The method of claim 10, further comprising the step of: Tracking a current speed of the laser brazing / welding process; and Providing independent and adaptive control of the first signal-on channel (90) in proportion to the speed of the laser brazing / welding process. [12] The method of claim 11, wherein the step of synchronizing the execution timing of the first signal value channel is automatically updated in response to a change in the welding sequence. [13] The method of claim 12, wherein the welding sequence comprises a laser brazing / welding start command (52) and a laser brazing / welding stop command, and wherein an execution of the first signal value channel is automatically adaptively controlled in response to an acceleration in response to the laser brazing / welding start command (52), and wherein an execution of the first signal value channel is automatically adaptively controlled in response to a deceleration in response to the laser brazing / welding stop command. [14] Apparatus for adaptively controlling a robotic laser brazing / welding process, comprising: a robot control device (10); a robot arm (12) carrying a brazing / welding tool connected to the control unit; a non-volatile memory element (18) connected to the control unit (10) and stores a software program executed by the control unit for coordinating a movement of the robot, the software program generating process signals executable during the robot operation, including one or more execution commands defined in a welding sequence; and a first signal-value channel for controlling at least one process parameter (20) of the laser brazing / welding, the first signal-value channel being subject to a first waiting time (t1) in relation to the one or more execution commands; wherein the software program synchronizes an execution timing of the first signal-value channel with the one or more execution instructions by adjusting the execution timing of the first signal-value channel relative to the one or more execution instructions by the size of the first wait time (t1). [15] The apparatus of claim 14, wherein the software program tracks an actual laser brazing / welding speed and provides independent and adaptive control of the first signal value channel in proportion to the actual laser brazing / welding speed. [16] The apparatus of claim 15, wherein the software program automatically updates an execution timing of the first signal value channel in response to a change in the welding sequence. [17] The apparatus of claim 14, further comprising: a first signal-on channel (90) for controlling the at least one process parameter (20) of the laser brazing / welding process, wherein the first signal-on channel (90) is subject to a second wait time (t2) relative to the one or more execution commands; wherein the software program synchronizes an execution timing of the first signal-on channel (90) with the one or more execution instructions by adjusting the execution timing of the first signal-on channel (90) relative to the one or more execution instructions by the size of the second wait time (t2). [18] The apparatus of claim 17, wherein the software program tracks an actual laser brazing / welding speed and provides independent and adaptive control of the first signal-value channel and the second signal-on channel (90) in proportion to the actual laser brazing / welding speed. [19] Apparatus according to claim 18, wherein the at least one process parameter (20) of the laser brazing / welding process is one of laser power, laser on / off, wire feed speed, wire feed on / off, double wire feed speed, double wire feed on / off, gas flow, gas flow on / off, gas velocity, gas pressure, gas temperature, wire temperature, wire preheating and wire preheating on / off. [20] The apparatus of claim 18, wherein the software program provides independent and adaptive control of the first signal value channel by applying to the first signal value channel one of a proportional control method, a time-linear zero-rise control method, an automatic linear rise control method, a user linear rise control method, and a rate-linear rise control method.

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