Sound-based weld travel speed sensing system and method

A weld travel speed sensing system includes at least one sound sensor configured to sense a sound generated to allow determination of a position of a welding torch. The weld travel speed sensing system is configured to determine a position of a point on the welding torch based on the sensed sound.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Non-Provisional Patent Application of U.S. Patent Application No. 61/597,556, entitled “Weld Travel Speed Sensing Systems and Methods”, filed Feb. 10, 2012, which is herein incorporated by reference.

BACKGROUND

The invention relates generally to welding systems, and, more particularly, to sensing systems for monitoring a travel speed of a welding torch during a welding operation.

Welding is a process that has become ubiquitous in various industries for a variety of types of applications. For example, welding is often performed in applications such as shipbuilding, aircraft repair, construction, and so forth. While these welding operations may be automated in certain contexts, there still exists a need for manual welding operations. In some manual welding operations, it may be desirable to monitor weld parameters, such as the travel speed of the welding torch, throughout the welding operation. While the travel speed of an automated torch may be robotically controlled, the travel speed of the welding torch in manual operations may depend on the operator's welding technique and pattern. Unfortunately, it may be difficult to measure this weld motion during a welding operation due to features of the welding environment, operator considerations, and so forth.

BRIEF DESCRIPTION

In a first embodiment, a weld travel speed sensing system includes at least one sound sensor configured to sense a sound generated to allow determination of a position of a welding torch. The weld travel speed sensing system is configured to determine a position of a point on the welding torch based on the sensed sound.

In another embodiment, a weld travel speed sensing system includes at least one sound sensor configured to sense a sound emitted from a welding arc produced by a welding torch. The weld travel speed sensing system is configured to determine a position of the welding arc based on the sensed sound.

In a further embodiment, a method includes determining, via a sound sensor associated with a welding system, a sensor signal indicative of a sound emitted for determination of a position of a welding torch of the welding system. The method also includes determining, via a processing system, a position of a point on the welding torch based at least in part on the sensor signal.

DETAILED DESCRIPTION

As described in detail below, provided herein are systems and methods for determining the travel speed of a welding device during a welding operation. The foregoing systems and methods may be used separately or in combination to obtain information during the welding operation relating to the three dimensional position of a point on the welding torch. The change in this position with respect to time may be used to determine the speed of the welding torch along the surface of the metal being welded, and this weld travel speed may be utilized to evaluate the heat input to a welding workpiece at a given time. The monitored position of one or more points on the welding torch may be used to determine other parameters as well, including orientation, travel direction, and velocity of the welding torch. In some embodiments, the methods described herein may be utilized in unconstrained or manual welding operations to offer advantages over traditional systems in which it may be difficult to measure the weld motion. However, the foregoing systems and methods may be utilized in a variety of suitable welding systems, such as automated or robotic systems.

Present embodiments are directed toward systems and methods for sensing a travel speed of a welding torch using a sound-based detection system. More specifically, the disclosed systems include a travel speed sensing system that monitors a sound associated with the welding system via at least one sound sensor, and detects or determines a travel speed of the welding torch based on the monitored sound. In some embodiments, the travel speed sensing system may include an array of sound sensors (e.g., microphones) located throughout a weld area, and the sound sensors detect a sound emitted from the welding torch. The term “array” in the following discussion refers to an arrangement of two or more elements (e.g., sensors, emitters) that may be located in fixed or unfixed positions relative to one another. In other embodiments, a single sound sensor may be disposed on the welding torch, and an array of sound emitting devices may be located throughout the weld area. By monitoring a change in time of flight of one or more emitted sounds to one or more sensors throughout the system, the travel speed sensing system may determine a change in spatial location of the welding torch with respect to time.

Turning now to the figures,FIG. 1is a block diagram of an embodiment of a welding system10in accordance with the present techniques. The welding system10is designed to produce a welding arc12on a workpiece14. The welding arc12may be of any type of weld, and may be oriented in any desired manner, including MIG, metal active gas (MAG), various waveforms, tandem setup, and so forth. The welding system10includes a power supply16that will typically be coupled to a power source18, such as a power grid. Other power sources may, of course, be utilized including generators, engine-driven power packs, and so forth. In the illustrated embodiment, a wire feeder20is coupled to a gas source22and the power source18, and supplies welding wire24to a welding torch26. The welding torch26is configured to generate the welding arc12between the welding torch26and the workpiece14. The welding wire24is fed through the welding torch26to the welding arc12, molten by the welding arc12, and deposited on the workpiece14.

The wire feeder20will typically include control circuitry, illustrated generally by reference numeral28, which regulates the feed of the welding wire24from a spool30, and commands the output of the power supply16, among other things. Similarly, the power supply16may include control circuitry29for controlling certain welding parameters and arc-starting parameters. The spool30will contain a length of welding wire24that is consumed during the welding operation. The welding wire24is advanced by a wire drive assembly32, typically through the use of an electric motor under control of the control circuitry28. In addition, the workpiece14is coupled to the power supply16by a clamp34connected to a work cable36to complete an electrical circuit when the welding arc12is established between the welding torch26and the workpiece14.

Placement of the welding torch26at a location proximate to the workpiece14allows electrical current, which is provided by the power supply16and routed to the welding torch26, to arc from the welding torch26to the workpiece14. As described above, this arcing completes an electrical circuit that includes the power supply16, the welding torch26, the workpiece14, and the work cable36. Particularly, in operation, electrical current passes from the power supply16, to the welding torch26, to the workpiece14, which is typically grounded back to the power supply16. The arcing generates a relatively large amount of heat that causes part of the workpiece14and the filler metal of the welding wire24to transition to a molten state, thereby forming the weld.

To shield the weld area from being oxidized or contaminated during welding, to enhance arc performance, and to improve the resulting weld, the welding system10also feeds an inert shielding gas to the welding torch26from the gas source22. It is worth noting, however, that a variety of shielding materials for protecting the weld location may be employed in addition to, or in place of, the inert shielding gas, including active gases and particulate solids.

Presently disclosed embodiments are directed to a sound-based travel speed sensing system used to detect a change in position of the welding torch26over time throughout the welding process. In some embodiments, the travel speed of the welding torch26may refer to a change in three dimensional position of the welding torch with respect to time. In other embodiments, the travel speed of the welding torch26may refer to a change in two dimensional position of the welding torch26within a plane parallel to a welded surface of the workpiece14. AlthoughFIG. 1illustrates a gas metal arc welding (GMAW) system, the presently disclosed techniques may be similarly applied across other types of welding systems, including gas tungsten arc welding (GTAW) systems and shielded metal arc welding (SMAW) systems. Accordingly, embodiments of the sound-based travel speed sensing systems may be utilized with welding systems that include the wire feeder20and gas source22or with systems that do not include a wire feeder and/or a gas source, depending on implementation-specific considerations.

FIG. 2is a block diagram of an embodiment of the welding system10, including a travel speed sensing system50in accordance with presently disclosed techniques. The travel speed sensing system50may include, among other things, a travel speed monitoring device52configured to process signals received from one or more sound sensors54disposed about a weld area56. The sound sensors54may be any desirable type of sensor that converts acoustic energy into an electrical signal. For example, the sound sensors54may include any number or arrangement of microphones disposed about the weld area56. The weld area56may include a weld cell within which a welding operator is using the welding system10to perform a welding operation. In some embodiments, the weld area56may include a surface or structure upon which the workpiece14is located throughout the welding process, or the workpiece14itself.

The sound sensors54may be used to monitor one or more sounds58generated to allow determination of a position of the welding torch26. The sounds58may come from one or more sound sources60within the weld area56. For example, the one or more sounds58may be emitted from one or more sound emitting devices disposed on the welding torch26, or from the welding arc12produced by the welding torch26. In other embodiments, the sounds58may be emitted from one or more sound emitting devices disposed about the weld area56external to the welding torch26. Each of the sound sensors54may convert the acoustic energy of the sound waves58incident on the sound sensor54into an electrical signal62. The travel speed sensing system50may then transmit the signal62to a processor64of the travel speed monitoring device52. In certain embodiments, the one or more sounds58associated with the welding system10are distinguishable, via the travel speed sensing system50, from one or more sounds associated with additional welding systems that may be located nearby.

As shown, the travel speed monitoring device52may include the processor64, which receives inputs such as sensor data from the sound sensors54via the signal62. Each signal62may be communicated over a communication cable, or wireless communication system, from the one or more sound sensors54located throughout the weld area56. In an embodiment, the processor64may also send control commands to a control device66of the welding system10in order to implement appropriate actions within the welding system10. For example, the control device66may control a welding parameter (e.g., power output, wire feed speed, gas flow, etc.) based on the determined travel speed of the welding torch26. The processor64also may be coupled with a display68of the travel speed monitoring device52, and the display68may provide a visual indicator of the travel speed of the welding torch26based on the determined travel speed.

Further, the processor64is generally coupled to a memory70, which may include one or more software modules72that contain executable instructions, transient data, input/output correlation data, and so forth. The memory70may include volatile or non-volatile memory such as magnetic storage memory, optical storage memory, or a combination thereof. Furthermore, the memory70may include a variety of machine readable and executable instructions (e.g., computer code) configured to provide a calculation of weld travel speed, given input sound-based sensor data. Generally, the processor64receives such sensor data from the one or more sound sensors54in the weld area56, and references data stored in the memory70to implement such calculation. In this way, the processor64is configured to determine a travel speed of the welding torch26, based at least in part on the signal62.

In some embodiments, the travel speed sensing system50may be provided as an integral part of the welding system10ofFIG. 1. That is, the travel speed sensing system50may be integrated into a component of the welding system10, for example, during manufacturing of the welding system10. For example, the power supply16may include appropriate computer code programmed into the software to support the travel speed sensing system50. However, in other embodiments, the travel speed sensing system50may be provided as a retrofit kit that may enable existing welding systems10with the sound-based travel speed sensing capabilities described herein. The retrofit kit may include, for example, the travel speed sensing system50, having the processor64and the memory70, as well as one or more sound sensors54from which the travel speed sensing system50receives sensor input. In some embodiments, the retrofit kit may also include the welding torch26, having the sound sensor54or sound emitting device installed thereon. To that end, such retrofit kits may be configured as add-ons that may be installed onto existing welding systems10, providing travel speed sensing capabilities. Further, as the retrofit kits may be installed on existing welding systems10, they may also be configured to be removable once installed.

FIG. 3is a process flow diagram of an embodiment of a method90for detecting the travel speed of the welding torch26using the travel speed sensing system50. The method90includes various blocks that may be implemented via the travel speed monitoring device52. More specifically, the method90may be implemented as a computer or software program (e.g., code or instructions) that may be executed by the processor64to execute one or more of the steps of the method90. Additionally, the program (e.g., code or instructions) may be stored in any suitable article of manufacture that includes at least one tangible non-transitory, computer-readable medium that at least collectively stores these instructions or routines, such as the memory70or another storage component of the travel speed monitoring device52. The term non-transitory indicates that the medium is not a signal.

The method90includes comparing (block92) times of arrival of one or more sounds58to one or more sound sensors54based on the signals62from the sound sensors54. The travel speed monitoring device52may perform this comparison by analyzing the signals62to detect the times at which an identifiable characteristic of the sound58associated with the welding system10reaches each sensor54. In some embodiments, the sound58associated with the welding system10may be identifiable by the travel speed sensing system50based on a pulse, a chirp, a delay, a waveform, a frequency content, a sound wave shape, a pulse pattern, or some combination thereof. Times of arrival may then be compared to determine a relative time of arrival of each sound58to each sound sensor54. The method90may include trilateration (block94) of a position of a point on the welding torch26based on the compared time of arrival, or time of flight. Time of flight of the sound waves58is proportional to the distance from the sound source60to the sound sensor54. Therefore, it may be possible to determine a three dimensional position of the point on the welding torch26based on the relative times of arrival of the sounds58to the sound sensors54.

In addition, the method90includes determining (block96) the travel speed of the welding torch26by detecting a change in position of the point on the welding torch26with respect to time. This may involve processing signals received from the one or more sound sensors54at a regular time interval. The processor64may determine a change in the position of the welding torch26from signals received at two subsequent times, and divide this change in position by the time interval. Other methods may be utilized to determine the change in position of the welding torch26with respect to time, thereby detecting the travel speed of the welding torch26.

FIG. 4illustrates the welding system10including components capable of determining a point on the welding torch26, and thus a travel speed of the welding torch26, in accordance with one embodiment. In the illustrated embodiment, the one or more sound sensors54includes a six element microphone array110, which includes a first microphone112, a second microphone114, a third microphone116, a fourth microphone118, a fifth microphone120, and a sixth microphone122. The microphone array110surrounds the welding area56, which includes the workpiece14(e.g., a metal plate) being welded. The welding torch26produces the welding arc12between a tip of the welding torch26and the current location of the applied weld.

In the illustrated embodiment, the sound58comes from a single sound source60, which is the welding arc12. As indicated by semicircles, the sound waves58are emitted from the welding arc12and reach one or more of the microphones in the microphone array110. The sound58arrives at each microphone at a time proportional to a distance between the welding arc12and each microphone. For example, the sound58arrives at the microphone112at a time proportional to a distance124between the welding arc12and the microphone112. Similarly, distances126and128determine the time at which the sound58reaches the microphones114and116, respectively. The current sound location of the welding arc12may be defined by the region where spherical surfaces130,132, and134intersect. The spherical surfaces130,132, and134are associated with the distances124,126, and128from each of the microphones112,114, and116, respectively. Weld travel speed may be derived from changes in time of the position of the three dimensional sound located welding arc12.

More specifically, the sound58emitted by the welding arc12may be detected by the array110of microphones with known relative positions. Features of the sound58may be used to determine relative timing of sound arrival and therefore distances, or changes in distances, between the welding arc12and the array110of microphones. In some embodiments, such features of the sound58may include natural fluctuations in the welding arc12, which provide an inherent modulation in the sound58emitted from the welding arc12. For example, the natural fluctuations of the welding arc12may emit a unique sound over time, based on fluctuating plasma in the welding arc12or spatter output during weld formation. In other embodiments, the sound58may be augmented by modulating the weld current over time to create a marker, pulse, or sound pattern that may be more easily identified and whose time of detection may be more precisely determined. Further, in another embodiment, the sound58may be augmented by attaching a sound emitting device to the welding torch26. Indeed, in some embodiments, it may be desirable to have one or more features in the sound signal that enable the determination of when the same feature or features is detected at different nearby sound sensors54.

In the embodiment illustrated inFIG. 4, the microphone array110is placed around the periphery of the weld area56to detect the sound58emitted from the welding arc12. The microphones112,114,116,118,120, and122are used to concurrently measure the sound signal reaching each respective microphone. In certain embodiments, the time between sound emission and reception may be used to determine the approximate distance (e.g., distances124,126, or128) from each microphone to the sound source60. The distance124,126, or128defines a radius of a time of flight sphere for each microphone, each time of flight sphere defining a spherical surface upon which the sound source60is located. The intersection point of the spherical surfaces (e.g.,130,132, and134) from several microphones defines the current location of the sound source60. In certain embodiments, during operation, the spherical surfaces130,132, and134may not all intersect at the same location and, therefore, such surfaces may define a region near their intersections (or between near miss intersections), and the sound source60may be assumed to be in this location. Accordingly, the average or centroid of this intersection zone may be defined as the current estimate of the location of the point on the welding torch26or the welding arc12. A number of trilateration algorithms exist that could be applied to determine a best estimate location for the current position. In this way, the weld torch position may be estimated over time during a weld operation. The change in position divided by the change in time that elapsed since the last determination of position provides an indication of the three-dimensional weld travel speed of the welding torch26.

In some embodiments, to facilitate timing of the arrival of a sound feature at each microphone, it may be desirable to have a pulse with fast rise time or other higher frequency components that create an edge, peak, or other rapidly changing inflection feature. The travel speed monitoring device52may determine a time of arrival (or time of flight) by analyzing the magnitude, edge, peak, derivative, or other features of the sound pulse/wave. In other embodiments, the travel speed monitoring device52may analyze sound phase delays or sound group delays when transmitting the sound in a semi-continuous or full-continuous mode. Alternatively, in another embodiment, a segment of the signal with unique time-based features may be identified for timing analysis using cross correlation techniques on a segment of the signal. Still further, in another embodiment, the signal might be band pass filtered at one or more frequency bands to accentuate or isolate some frequency band prior to timing or cross correlation analysis between the microphone signals. Sound magnitude measurements may be utilized in certain embodiments. This involves determining a position based on a sound pressure level (loudness) of the sound58when it hits the one or more sensors54. The detected sound58may have a lower sound pressure level according to the distance it traveled from the sound source60to the sound sensor54. Additionally, in some embodiments, it may be desirable to utilize ultrasonic sound frequencies to create a sound feature. Using an ultrasonic frequency signal for sound timing determination may enable relatively easy processing, via isolation of the high frequency signal, without increasing the audible noise of the welding system10.

It should be noted that the placement of the microphone array110may be subject to a variety of implementation-specific variations. For example, in one embodiment, the individual microphones may be spaced around the weld area56and may or may not be located in the same plane. Further, although six microphones are provided in the illustrated embodiment, it should be noted that any suitable number of microphones may be provided in other embodiments. Additionally, instead of positioning a plurality of individual microphones around the welding area, in some embodiments, the microphone array110may include a plurality of sub-arrays of microphones positioned about the weld area56of interest. In such embodiments, beamforming or holographic methods may be employed to localize the sound. Beamforming methods may involve processing signals from the microphones in each subarray to account for acoustic interference within the sound58traveling to the subarray.

In still other embodiments, there may be an additional microphone (not shown) disposed on the welding torch26, which is not in a fixed relative position to the other microphones of the microphone array110. This additional microphone may be located near the torch tip, relatively close to the welding arc12. The travel speed monitoring device52may compare a time of arrival of the sound58to this microphone with the time of arrival of the sound58to each of the fixed microphones. As a result, the position determination of the welding arc12may account for the speed of the sound58traveling from the welding arc12to each microphone.

In certain welding environments, there may be multiple welding systems10being utilized in relatively close proximity. In such instances, sounds58emitted from one welding system10may enter the weld area56of an adjacent welding system10and be picked up by the sound sensors54located about the weld area56. To keep acoustic interference of the sounds58from affecting the travel speed detection, it may be desirable to distinguish the sounds58emitted from each different welding system10located in a welding environment. This allows the travel speed monitoring device52to isolate the sound58emitted from the corresponding welding system10from other sounds emitted from other systems. To accomplish this, any distinguishing signal emitted from the sound source60may be unique to the corresponding welding system10. For example, it may be desirable to superimpose a distinguishing signal on the welding power from the power supply16(e.g., via current modulation). Each power supply16may be associated with a distinct signal, thus enabling detection of which signal originated from which power supply16. In embodiments with a sound emitter located on the welding torch26, the emitter may output a pattern of chirps or pulses that is unique to the welding torch26. In still other embodiments, acoustic interference may be overcome by using highly directional microphones to detect the sound58emitted from a particular welding system10. The microphone array110may be positioned so that only sounds58that hit the microphone from a specific direction are detected. In this way, the sounds58from each of the welding systems10do not have to be unique, because the directional microphones pick up the sounds emitted directly from their specific weld area56.

As mentioned above, the sound source60that outputs the sound58for determining travel speed of the welding torch26may include an emitter disposed on the welding torch26.FIG. 5illustrates one such embodiment, including the microphone array110for sensing the sound58emitted from a sound emitting device150disposed on the welding torch26. The sound58emitted from the sound emitting device150may be distinguishable from the sound emitted from the welding arc12produced via the welding torch26. For example, the sound emitting device150may output a pulse, chirp, ultrasonic signal, or another sound that is identifiable with respect to time, so that arrival times of the sound58to each of the microphones can be compared. In some embodiments, a single omni-directional sound emitter may be used. However, in other embodiments, multiple sound emitters may be collocated and disposed on the welding torch26, near a single location. In such embodiments, each emitter may be configured to output sound energy in a directed cone-like pattern. These multiple emitters could be arranged to point in multiple directions and to emit identical sounds at the same instant, providing a more omni-directional sound emission pattern. By using multiple sound emitters, it may be possible to achieve wider directionality in the emitted sound than would be possible with a single directional sound emitter, such that the sound may be easily detected by all elements in the microphone array110.

It should be noted that in some embodiments, it may be desirable to reduce or eliminate the likelihood of weld travel speed errors due to the sound emitting device150being positioned far from the welding arc12. Accordingly, in the illustrated embodiment, one or more sensors152(e.g., triaxial accelerometers, electrolytic tilt sensors, etc.) may be placed on the welding torch26to provide the travel speed monitoring device52with a current torch angle154of the welding torch26in the earth's gravitational field. In such an embodiment, measured changes in the torch angle154may be detected by these sensors152, and the travel speed sensing device52may determine the position of a point (e.g., tip) on the welding torch26based in part on the torch angle154. In this way, corrections may be made to the weld travel speed based upon the geometry of the sound emitter mounting location (e.g., distance156) relative to the torch tip and the measured three-dimensional torch angle154. In some embodiments, multiple sound emitting devices150may be disposed at different points on the welding torch26. The travel speed monitoring device52may determine positions of two or more points on the welding torch26(where the sound emitting devices150are located), based on the detected sound. The travel speed monitoring device52may use this position information to determine an orientation of the welding torch26with respect to the workpiece14. In certain contexts. As noted above, the orientation may be utilized for correcting a weld travel speed calculation performed via the travel speed monitoring device52.

FIG. 6illustrates another embodiment of the welding system10including components capable of determining a position of a point on the welding torch26, and thus the travel speed of the welding torch26. As shown, the sound source60of the illustrated embodiment is a sound element emitter array170, which includes emitter elements172,174,176,178,180, and182whose relative positions are determined. The emitter array170is shown surrounding the weld area56defined by the workpiece14being welded using the welding torch26. In the illustrated embodiment, an omni-directional (i.e., a random incidence) microphone184is mounted to the welding torch26. Sounds58emitted by one or more emitter elements of the emitter array170may reach the microphone184. For example, in the illustrated embodiment, sound58emitted by emitter elements172,174, and176reach the microphone184. Because the microphone184and the sound emitters172,174,176,178,180, and182may be connected to the same electronics (e.g., travel speed monitoring device52), the time between sound emission from each emitter and the detection by the microphone184may be determined. Further, radial distances186,188, and190between the microphone184and each emitter may be calculated from the time delay. Therefore, the position of the microphone184, which corresponds to the approximate location of the welding arc12, may be determined by time of flight trilateration, and the three-dimensional speed of the microphone184may be calculated over time to provide an indication of welding torch travel speed during a welding operation.

In the embodiment illustrated inFIG. 6, as compared toFIGS. 4 and 5, the location of the sound source60(e.g., emitters, welding arc12) and sound sensors54(e.g., microphones) are reversed. That is, in this embodiment, the sound emitters172,174,176,178,180, and182are located around the weld area56, and the one or more microphones184are placed at specific points on the welding torch26to receive the emitted sounds. In embodiments where a single microphone184is located on the welding torch26, the microphone184may provide a signal to the travel speed monitoring device52for processing. The travel speed monitoring device52may separate the sounds58from each of the sound emitters170to determine relative times of arrival of the sounds58at the microphone184. In embodiments where multiple sound sensors54(e.g., microphones) are disposed at different points on the welding torch26, the travel speed monitoring device52may receive signals from each of the sound sensors54. The travel speed monitoring device52may determine, based on the multiple signals, an orientation of the welding torch26in the earth's gravitational field. In certain contexts, the orientation may be utilized for correcting a weld travel speed calculation performed via the travel speed monitoring device52.

In certain embodiments, it may be desirable for the sound emitters170to be distinctly recognizable by the microphone184. To this end, in some embodiments, each emitter may produce a different waveform in time (frequency/waveform separation). In other embodiments, the sound emitters170may produce sequential sounds with an appropriate delay between each sound emission (time separation). Further, a time domain waveform may be encoded by a given frequency content or shape over time, thus enabling the individual pulses to be identified even if they arrive at the microphone184superimposed. Additionally, in another embodiment, each emitter may produce a distinctly shaped sound wave, such as a triangle wave, square wave, sine wave, or other shaped wave or pulse, having a varied time, width, or repeated pattern (with unique timing, shapes, frequencies and/or amplitudes) that renders the wave identifiable. Such techniques may be applied across emitters arrays170used for different welding systems10or in different weld cells that are located in close proximity, to reduce an effect of acoustic interference.

A combination of techniques may be used to identify one or more sounds when unique pulses or pulse/wave patterns are utilized for distinguishing the sounds. These distinguishable sounds may be from different sound emitting devices (as shown inFIG. 6), or they may be from different welding systems altogether (as described with reference toFIG. 4). In an embodiment, the signal received by the sound sensor54may be bandpass filtered to isolate the signal from noise. Then, a form of pattern matching may be applied to the signal to identify which of the sounds received by the sound sensor54is the one associated with the desired welding torch26or sound emitting device. Any number of different pattern matching techniques may be used, including simple template comparisons and convolutions. More complicated pattern matching techniques may include combinations of steps, such as performing feature extractions followed by statistical pattern recognition or neural network pattern matching. These and any other appropriate pattern matching techniques may be implemented via the processor64of the travel speed monitoring device52to separately identify a desired sound emitted for determination of weld torch position and travel speed.

It should be noted that in some embodiments, it may be desirable to reduce or eliminate the likelihood of weld travel speed errors due to the microphone184being positioned far from the welding arc12. As described in reference toFIG. 5, the one or more sensors152(e.g., triaxial accelerometers, tilt sensors) may be placed on the welding torch26to provide the travel speed monitoring device52with the torch angle154in the earth's gravitational field. Corrections may be made to the weld travel speed based upon the geometry of the microphone mounting location (e.g., distance156) relative to the torch tip and the measured three-dimensional torch angle154.

In embodiments having electronic components mounted to the welding torch26, it may be desirable for such components to be appropriate for the welding environment. These components may include, for example, the microphone184, the sound emitting device150, and/or the sensors152. The components may be configured to withstand shock from the welding torch26impacting the workpiece14or other components in the weld area56. In addition, the components may be capable of operating without electromagnetic interference and within high temperature environments, such as may be encountered during the welding process.

It may be desirable that the array (e.g., microphone array110ofFIG. 4, emitter array170ofFIG. 6) be configured to perform self-calibration of the relative positions of the microphones and/or emitters of the array, since the array defines the coordinate system by which the travel speed is measured. If the array cannot self-calibrate the relative position of each member of the array, then for some embodiments (as described above), the elements of the array may be precisely positioned relative to one another in a known configuration. In other embodiments, the method for self-calibration may involve each array element having both a sound receiver and sound transmitter. These may be the same element, in cases where the technology allows the element to function as both an emitter and receiver of sound pulses, or this may be implemented via a collocated transmitter and receiver at each array position. In either case, one array element can be defined as the origin for a coordinate system. Then the distance between each element of the array and every other element can be calculated by each array element producing a sound, one at a time, at a known instant while all other elements determine the time for the sound to reach them. The time delay of this sound arrival may then be converted to a distance from the sound emitting element and each other array element by multiplying by the speed of sound. With the distance between all points of the array known, it is possible to solve for the position of all array elements relative to the origin element by using trilateration techniques. A coordinate system may also be devised, if desired, using arbitrary elements of the array, where any two elements can define a coordinate system axis and any three elements can define a coordinate system plane. This technique may allow the array elements to be imprecisely placed around the welding area56and then the travel speed sensing system50can self-determine the array element positions upon demand. With the relative position of all array elements known, the torch position can be accurately determined by trilateration. Accidental or purposeful movement of one or more array elements may be quickly accounted for by this self-calibration technique, so that the travel speed sensing system50self-maintains its calibrated weld travel speed measurement.