Method and system for inspecting laser welds connecting pole regions of a current collector to poles of a stack of battery cells

Abstract

There is described a method for inspecting laser welds connecting pole regions of a current collector to poles of a stack of battery cells when the pole regions are located adjacent to and aligned with corresponding ones of the poles. The method generally has: moving an end effector towards a given pole region of the current collector, the end effector having a body, and a laser aperture extending across the body, said moving including exposing the given pole region via the laser aperture; directing a laser beam across the laser aperture and forming a laser weld at the given pole region; projecting an illumination beam towards the laser weld; and capturing an image of the laser weld during said illuminating, the image including the laser weld and surrounding given pole region; the laser weld being inspectable based on the image.

Description

METHOD AND SYSTEM FOR INSPECTING LASER WELDS CONNECTING POLE REGIONS OF A CURRENT COLLECTOR TO POLES OF A STACK OF BATTERY CELLSFIELD

[0001] The improvements generally relate to energy storing systems and more specifically to the manufacturing of a battery module.BACKGROUND

[0002] Typically, energy storing systems include one or more packs of multiple battery modules, with each battery module containing a number of battery cells held in an arrayed configuration relative one another (i.e., stacked), and a current collector connecting the battery cells in an electrical circuit. Among the existing various types of battery cells used in battery modules, cylindrical geometries are perhaps the most widely used. In some markets, such as electrical vehicles for instance, a widely used format has cylindrical geometries with both the positive pole and the negative pole accessible at the same end, which can be referred to as the pole end. Such as shown in the example presented in Figs. 1 , 1 A and 1 B, the battery cells can be stacked with the axes of the battery cells parallel to one another, the pole ends all facing the same side, and the pole ends are aligned within a common pole plane extending normal to the axes.

[0003] A component typically referred to as a current collector can be used to connect the battery cells, and more specifically the battery poles, in the electrical circuit. The current collector can be provided in the form of a sheet-like element having independent conductive paths with positive and negative pole regions. The current collector can be aligned parallel to the common pole plane and positioned adjacent the poles of the battery cells, with the pole regions of the current collector welded to corresponding ones of the poles of the battery cells.

[0004] The current collector and the battery cells are manufactured individually from one another and assembled to one another by a welding step. The welding step involves as many independent welds as there are pole regions and poles to be welded. Moreover, the battery cells are typically at least partially charged during the welding operation, since for many battery types, leaving a battery uncharged for extended periods of time may render it inoperable.Henceforth, the welding operation may involve positioning the stacked battery cells in a welding area of a welding system, with the poles facing upwardly and the current collector extending above the poles, with the pole regions vertically aligned with corresponding ones of the poles, and welding pole / pole region pairs to one another one by one until all the poles are welded to corresponding pole regions of the current collector, into a battery module configuration.

[0005] Although existing welding techniques were satisfactory to a certain degree, there always remained room for improvement, especially in the inspection of the welds once made.SUMMARY

[0006] In the context of migrating an increasing portion of energy consumption from fossil fuel energy towards electrical energy, manufacturing energy storing systems as efficiently as possible is desirable, which can involve different aspects. For instance, some standardized battery cell formats, such as the cylindrical formats 21700, 18650 and 4680, other cylindrical formats having their positive and negative poles on a respective end of the battery cell, prismatic formats, are becoming more and more popular. These three standardized formats have a generally cylindrical body, a protrusion located on the center of a first generally diskshaped pole end and forming a positive electric pole, and a negative electric pole embodied as an annular tip of a peripheral wall surrounding but radially separated from the positive pole, such as shown in Figs. 1A and 1 B, with the radial spacing being visible on Fig. 1A.

[0007] Welding pole regions of the current collector to poles of the battery cells using a laser can be particularly interesting from a point of view of precision and efficiency. However, it can be required to press the pole region against the corresponding pole prior to activating the laser beam for welding, to ensure that the pole region and pole have a satisfactory contact when heated by the laser. This raises the challenge of applying the pressure in a suitable way, i.e. , in a relatively balanced way and sufficiently close to the region being welded, while not interfering with the path of the laser beam. Moreover, from a productivity standpoint, there can be a desire to perform all the welds in a manner which meets the specifications as fast as possible. To do so, it was found convenient to use an end effector which can be moved by a robotized arm to press a given pole region against a corresponding underlying pole in a waywhich can expose the given pole region to a laser welder via a laser aperture, for instance. Once the given pole region is laser welded to the corresponding pole, the robotized arm can move the end effector towards another pole region and press it against a corresponding pole for laser welding, and so forth, until all the pole regions are properly welded to their corresponding poles. More than one robot can be used simultaneously to increase throughput.

[0008] Laser weld lines produced by such a manufacturing process are generally inspected in a post-manufacturing step, well after the actual laser welding process. However, such techniques can be viewed as inefficient in practice as whenever a weld line is deemed defective, then the whole battery module has to be repositioned under the welding area for corrective laser welding steps to be made. This disclosure presents a computer vision based inspection step performed immediately after the laser welding of any given pole region to a corresponding pole. Accordingly, if a laser weld is deemed defective, then it can be corrected on-the-go, thereby rendering the whole laser welding process more efficient. The inspected step described herein involves the use of an illuminator illuminating the given pole region, and its laser weld, across the laser aperture of the end effector while it is pressed against the periphery of the given pole region. Then, a camera captures an image of the given pole region while it is illuminated by the illumination beam. By capturing images of recently laser welded pole regions under uniform and constant illuminating conditions, it was found that the resulting images could be free from shadows or other undesired optical artifacts, which would otherwise impede the computer vision steps and also cause inaccurate laser weld inspection results. Accordingly, it was found preferable to ensure that uniform and constant illumination is projected across the laser aperture of the end effector, towards the given pole region and its laser weld, during the image capture so as to provide images of similar illuminating conditions. To this effect, it was found preferable to mount the illuminator directly to the end effector, with the illumination beam being projected at an angle towards the laser aperture so as to be cleared from a laser beam path at all times. By doing so, should the image processing steps identify that corrections are deemed necessary for one or more pole regions, then they can be corrected right away, or after a few other pole regions or all the other pole regions have been laser welded, while the battery module is still positioned under the welding area.

[0009] In accordance with a first aspect of the present disclosure, there is provided a method for inspecting laser welds connecting pole regions of a current collector to poles of a stack of battery cells, the current collector and battery cells received at a welding area with the pole regions located adjacent to and aligned with corresponding ones of the poles, the method comprising: using a first robot, moving a first end effector within the welding area towards a given pole region of the current collector, the first end effector having a body, and a laser aperture extending across the body, said moving the first end effector including exposing the given pole region via the laser aperture; using a scanning head of a laser welder, directing a laser beam across the laser aperture and forming a laser weld at the given pole region; using an illuminator, projecting an illumination beam for illuminating the laser weld; and using a camera, capturing an image of the laser weld during said illuminating, the image including the laser weld and surrounding given pole region, the laser weld being inspectable based on the image.

[0010] Further in accordance with the first aspect of the present disclosure, the illuminator and the camera can for example be mounted to a second end effector movable by a second robot independent from the first robot.

[0011] Still further in accordance with the first aspect of the present disclosure, the method can for example further comprise: after said directing, the first robot moving the first end effector away from the given pole region; and prior to said projecting the illumination beam and said capturing the image, the second robot moving the second end effector towards the given pole region.

[0012] Still further in accordance with the first aspect of the present disclosure, said moving the first end effector away from the given pole region and said moving the second end effector towards the given pole region can for example be performed simultaneously without physically interfering with one another.

[0013] Still further in accordance with the first aspect of the present disclosure, the illuminator and the camera can for example be mounted to the body of the first end effector, the illuminator and the camera clearing a vertical projection of the laser aperture and located away from the laser beam during said directing.

[0014] Still further in accordance with the first aspect of the present disclosure, the method can for example further comprise: after said directing and prior to said projecting the illumination beam and said capturing the image, the first robot moving the laser aperture away from the given pole region while exposing the illuminator and the camera to the laser weld.

[0015] Still further in accordance with the first aspect of the present disclosure, said exposing the illuminator and the camera to the laser weld can for example include at least one of: rotating the first end effector about an axis perpendicular to the welding area and translating the first end effector along a plane parallel to the welding area.

[0016] Still further in accordance with the first aspect of the present disclosure, said first end effector can for example have a pressing element mounted to the body, said moving the first end effector can for example include the pressing element pressing a periphery of the given pole region of the current collector against a corresponding one of the poles.

[0017] Still further in accordance with the first aspect of the present disclosure, at least one of said illuminating and said capturing can for example be performed during said pressing.

[0018] Still further in accordance with the first aspect of the present disclosure, at least one of said illuminating and said capturing can for example be performed through the laser aperture.

[0019] Still further in accordance with the first aspect of the present disclosure, at least one of said illuminating and said capturing can for example be performed via the scanning head of the laser welder.

[0020] Still further in accordance with the first aspect of the present disclosure, the method can for example further comprise, using a processor of a computing device, inspecting the laser weld based on the image.

[0021] Still further in accordance with the first aspect of the present disclosure, said inspecting can for example include outputting a laser weld status indicative of a status of the laser weld.

[0022] Still further in accordance with the first aspect of the present disclosure, the laser welding system can for example further comprise, using a force detector, measuring a given force applied by the first end effector against a surrounding of the given pole region and generating a force signal indicative of the given force during said directing, said inspecting further based on the force signal.

[0023] Still further in accordance with the first aspect of the present disclosure, the method can for example further comprise, using a laser weld monitor (LWM) receiving one or more return signals from the given pole region during said directing, generating one or more LWM signals indicative of said one or more return signals, said inspecting further based on the one or more LWM signals.

[0024] Still further in accordance with the first aspect of the present disclosure, said outputting can for example include identifying the laser weld in the image, determining the weld status based on the identified laser weld in the image, and instructing the laser welder to perform a correction on said laser weld when the determined weld status requires correction.

[0025] Still further in accordance with the first aspect of the present disclosure, said inspecting can for example be performed by executing at least one of: one or more trained artificial neural networks, one or more support vector machines, and one or more capsulebased networks.

[0026] In accordance with a second aspect of the present disclosure, there is provided a laser welding system for inspecting laser welds connecting pole regions of a current collector to poles of a stack of battery cells, the current collector and battery cells received at a welding area with the pole regions located adjacent to and aligned with corresponding ones of the poles, the laser welding system comprising: a first robot having a first end effector having a body, and a laser aperture extending across the body, the first robot moving the body of the first end effector within the welding area towards a given pole region of the current collector, said moving the first end effector including exposing the given pole region via the laser aperture; a laser welder having an emitter emitting a laser beam, and a scanning head optically coupled to the laser emitter, the laser welder directing, via the scanning head, the laser beam across the laser aperture and forming a laser weld at the given pole region; an illuminatorprojecting an illumination beam for illuminating the laser weld; and a camera capturing an image of the laser weld during said illuminating, the image including the laser weld and surrounding given pole region, the laser weld being inspectable based on the image.

[0027] Further in accordance with the second aspect of the present disclosure, the laser welding system can for example further comprise a second robot independent from the first robot, the illuminator and the camera mounted to a second end effector movable by the second robot.

[0028] Still further in accordance with the second aspect of the present disclosure, the illuminator and the camera can for example be mounted to the body of the first end effector, the illuminator and the camera can for example clear a vertical projection of the laser aperture and located away from the laser beam during said directing.

[0029] Still further in accordance with the second aspect of the present disclosure, said illuminator and said camera can for example be mounted to the body of the first end effector via an arm protruding therefrom.

[0030] Still further in accordance with the second aspect of the present disclosure, said first end effector can for example have a pressing element mounted to the body, said moving the first end effector including the pressing element applying a pressure to a periphery of the given pole region, thereby forcing the given pole region against a corresponding one of the poles.

[0031] Still further in accordance with the second aspect of the present disclosure, at least one of said illuminating and said capturing can for example be performed through the laser aperture.

[0032] Still further in accordance with the second aspect of the present disclosure, at least one of said illuminating and said capturing the image can for example be performed via the scanning head of the laser welder.

[0033] Still further in accordance with the second aspect of the present disclosure, the laser welding system can for example further comprise a controller communicatively coupled to the camera, the controller having a processor and a non-transitory computer memory havingstored thereon instructions that when executed by the processor perform the step of: inspecting the laser weld based on the image.

[0034] Still further in accordance with the second aspect of the present disclosure, said inspecting can for example include outputting a laser weld status indicative of a status of the laser weld.

[0035] Still further in accordance with the second aspect of the present disclosure, said outputting can for example include identifying the laser weld in the image, determining the weld status based on the identified laser weld in the image, and instructing the laser welder to correct said laser weld when the determined weld status requires correction.

[0036] Still further in accordance with the second aspect of the present disclosure, said inspecting can for example be performed by executing at least one of: one or more trained artificial neural networks, one or more support vector machines, and one or more capsulebased networks.

[0037] In accordance with a third aspect of the present disclosure, there is provided a method for inspecting laser welds connecting pole regions of a current collector to poles of a stack of battery cells when the pole regions are located adjacent to and aligned with corresponding ones of the poles, the method comprising: moving an end effector towards a given pole region of the current collector, the end effector having a body, and a laser aperture extending across the body, said moving including exposing the given pole region via the laser aperture; directing a laser beam across the laser aperture and forming a laser weld at the given pole region; projecting an illumination beam; and capturing an image of the laser weld during said illuminating, the image including the laser weld and surrounding given pole region, the laser weld being inspectable based on the image. In some embodiments, the illumination beam can be projected through the laser aperture. Additionally or alternately, the image of the laser weld can be captured across the laser aperture.

[0038] Although battery modules are generally meant to be identical to one another, there still remains slight tolerances in the positioning and the orientation of the battery cells and of the current collector’s pole regions, often provided in the form of tabs which can unpredictablybend in any direction. To maximize manufacturing efficiency, it was found preferable in some embodiments to perform an individual assessment of such positioning and orientation for each battery cell prior to the laser welding. As such, a camera can be used to capture an image of the given pole region as it is pressed against the corresponding pole. The image includes the laser aperture and its surroundings immediately prior to laser welding. The laser welding step can thus be performed based on the captured image. Although satisfactory to a certain degree, such images may exhibit shadows in the image due to improper illuminating conditions, which can obscure the given pole region and its surroundings. Such images can significantly increase the image processing time, and often lead to inaccurate results. Accordingly, it was found preferable to ensure that uniform and constant illumination is projected across the laser aperture of the end effector, towards the given pole region and its surroundings, during the image capture so as to provide images of similar illuminating conditions, which can in turn expedite any image processing steps that are to be performed before the laser welding.

[0039] In accordance with a fourth aspect of the present disclosure, there is provided a method for welding pole regions of a current collector to poles of a stack of battery cells with a laser beam when the current collector and battery cells are received at a welding area with the pole regions located adjacent to and aligned with corresponding ones of the poles, the method comprising: using a robot, moving an end effector within the welding area towards a given pole region of the current collector, the end effector having a body, and a laser aperture extending across the body, said moving including exposing the given pole region via the laser aperture; using an illuminator, projecting an illumination beam thereby illuminating the given pole region; using a camera, capturing an image of the laser aperture including the given pole region during said illuminating; and using a scanning head of a laser welder, directing the laser beam across the laser aperture based on the image. In some embodiments, the illumination beam can be projected through the laser aperture. Additionally or alternately, the image of the laser weld can be captured across the laser aperture.

[0040] In accordance with a fifth aspect of the present disclosure, there is provided a laser welding system for welding pole regions of a current collector to poles of a stack of battery cells with a laser beam when the current collector and battery cells are received at a welding area with the pole regions located adjacent to and aligned with corresponding ones of thepoles, the laser welding system comprising: a robot having an end effector having a body, and a laser aperture extending across the body, the robot moving the body of the end effector within the welding area towards a given pole region of the current collector, said moving including exposing the given pole region via the laser aperture; an illuminator projecting an illumination beam thereby illuminating the given pole region; a camera captures an image including the given pole region during said illuminating; and a laser welder having an emitter emitting the laser beam, and a scanning head optically coupled to the laser emitter, the laser welder directing, via the scanning head, the laser beam across the laser aperture based on the image. In some embodiments, the illumination beam can be projected through the laser aperture. Additionally or alternately, the image of the laser weld can be captured across the laser aperture.

[0041] In accordance with a sixth aspect of the present disclosure, there is provided a method for inspecting laser welds connecting pole regions of a current collector to poles of a stack of battery cells, the current collector and battery cells received at a welding area with the pole regions located adjacent to and aligned with corresponding ones of the poles, the method comprising: using a first robot, moving a first end effector within the welding area towards a given pole region of the current collector, the first end effector having a first body, and a first aperture extending across the first body, said moving including exposing the given pole region via the first aperture; using a scanning head of a laser welder, directing a laser beam across the first aperture of the first end effector and forming a laser weld at the given pole region; the first robot moving the first end effector away from the given pole region; using a second robot, moving a second end effector within the welding area towards the given pole region of the current collector; using an illuminator mounted to the second end effector, projecting an illumination beam towards the laser weld thereby illuminating the laser weld; and using a camera mounted to the second end effector, capturing an image of the laser weld during said projecting the illumination beam, the image including the laser weld and surrounding given pole region, the laser weld being inspectable based on the image.

[0042] Further in accordance with the sixth aspect of the present disclosure, the method can for example further comprise, using a processor of a computing device, inspecting the laser weld based on the image.

[0043] Still further in accordance with the sixth aspect of the present disclosure, said inspecting can for example include outputting a laser weld status indicative of a status of the laser weld.

[0044] Still further in accordance with the sixth aspect of the present disclosure, said moving the first end effector away from the given pole region can for example be made without interference with said moving the second end effector towards the given pole region.

[0045] Still further in accordance with the sixth aspect of the present disclosure, said second end effector can for example have a second body, and a second aperture extending across the second body, said moving the second end effector including exposing the laser weld via the second aperture.

[0046] Still further in accordance with the sixth aspect of the present disclosure, said illuminating and capturing can for example be performed across the second aperture.

[0047] Still further in accordance with the sixth aspect of the present disclosure, said second end effector can for example have a pressing element mounted to the second body, said moving the second end effector including the pressing element pressing a periphery of the given pole region of the current collector against a corresponding one of the poles.

[0048] Still further in accordance with the sixth aspect of the present disclosure, said illuminating and capturing can for example be performed during said pressing using the second end effector.

[0049] Still further in accordance with the sixth aspect of the present disclosure, during said illuminating, the illuminator can for example have a given point of view and distance from the laser weld.

[0050] Still further in accordance with the sixth aspect of the present disclosure, said illumination beam can for example be a uniform illumination beam.

[0051] Still further in accordance with the sixth aspect of the present disclosure, said illuminator can for example have a plurality of light-emitting diodes (LEDs).

[0052] Still further in accordance with the sixth aspect of the present disclosure, the camera can for example be a high-resolution camera.

[0053] In accordance with a seventh aspect of the present disclosure, there is provided a laser welding system for inspecting laser welds connecting pole regions of a current collector to poles of a stack of battery cells, the current collector and battery cells received at a welding area with the pole regions located adjacent to and aligned with corresponding ones of the poles, the laser welding system comprising: a first robot having a first end effector having a first body, and a first aperture extending across the first body, the first robot moving the first end effector within the welding area towards a given pole region of the current collector, said moving including exposing the given pole region via the first aperture; a laser welder having an emitter emitting a laser beam, and a scanning head optically coupled to the laser emitter, the laser welder directing, via the scanning head, the laser beam across the laser aperture and forming a laser weld at the given pole region, the first robot moving the first end effector away from the given pole region after said laser weld has been formed; a second robot having a second end effector having mounted thereto an illuminator and a camera, wherein upon the second robot moving the second end effector towards the given pole region of the current collector, the illuminator projects an illumination beam towards the laser weld and the camera captures an image of the laser weld illuminated by the illumination beam , the image including the laser weld and surrounding given pole region, the laser weld being inspectable based on the image.

[0054] Further in accordance with the seventh aspect of the present disclosure, the laser welding system can for example further comprise a controller communicatively coupled to the camera, the controller inspecting the laser weld based on the image.

[0055] Still further in accordance with the seventh aspect of the present disclosure, said inspecting can for example include outputting a laser weld status indicative of a status of the laser weld.

[0056] Still further in accordance with the seventh aspect of the present disclosure, the controller can for example have a processor, and a non-transitory computer memory having stored thereon instructions that when executed by the processor perform one or more stepsof inspecting, said inspecting including identifying the laser weld in the image, determining the weld status based on the identified laser weld in the image, and instructing the laser welder to correct said laser weld when the determined weld status requires correction.

[0057] Still further in accordance with the seventh aspect of the present disclosure, said second end effector can for example have a second body, and a second aperture extending across the second body, said moving the second end effector including exposing the laser weld via the second aperture.

[0058] Still further in accordance with the seventh aspect of the present disclosure, said projecting the illumination beam towards the laser weld and capturing the image of the laser weld can for example be performed across the second aperture.

[0059] Still further in accordance with the seventh aspect of the present disclosure, said second end effector can for example have a pressing element mounted to the second body, said moving the second end effector including the pressing element applying a pressure to a periphery of the given pole region, thereby forcing the given pole region against a corresponding one of the poles, said illuminator and camera performing said projecting and said capturing, respectively, as the pressing element applies the pressure to the periphery of the given pole region.

[0060] Still further in accordance with the seventh aspect of the present disclosure, the illuminator can for example have a plurality of light-emitting diodes (LEDs).

[0061] Still further in accordance with the seventh aspect of the present disclosure, the camera can for example be a high-resolution camera.

[0062] In accordance with an eighth aspect of the present disclosure, there is provided a method for inspecting laser welds connecting pole regions of a current collector to poles of a stack of battery cells, the current collector and battery cells received at a welding area with the pole regions located adjacent to and aligned with corresponding ones of the poles, the method comprising: using a robot, moving an end effector within the welding area towards a given pole region of the current collector, the end effector having a body, and a laser aperture extending across the body, said moving including exposing the given pole region via the laseraperture; using a scanning head of a laser welder, directing a laser beam across the laser aperture of the end effector and forming a laser weld at the given pole region; using the robot, moving the body of the end effector away from the given pole region, said moving including exposing the laser weld to an illuminator and a camera mounted to the body of the end effector, the illuminator and the camera spaced away from the laser aperture; using the illuminator, projecting an illumination beam thereby illuminating the laser weld; and using a camera, capturing an image during said illuminating, the image including the laser weld and surrounding given pole region, the laser weld being inspectable based on the image.

[0063] Further in accordance with the eighth aspect of the present disclosure, the method can for example further comprise, using a processor of a computing device, inspecting the laser weld based on the image.

[0064] Still further in accordance with the eighth aspect of the present disclosure, said inspecting can for example include outputting a laser weld status indicative of a status of the laser weld.

[0065] Still further in accordance with the eighth aspect of the present disclosure, said moving the end effector within the welding area towards the given pole region of the current collector can for example include applying a pressure around the given pole region and against a corresponding one of the poles.

[0066] Still further in accordance with the eighth aspect of the present disclosure, said applying can for example be performed using a pressing element mounted to the body of the end effector.

[0067] Still further in accordance with the eighth aspect of the present disclosure, said illuminator and said camera can for example be mounted to the body of the end effector via an arm protruding from the body of the end effector.

[0068] Still further in accordance with the eighth aspect of the present disclosure, when the body of the end effector has been moved away from the given pole region, a field of view of the camera and the illumination beam of the illuminator can for example be directed towards the laser weld along a vertical orientation.

[0069] Still further in accordance with the eighth aspect of the present disclosure, when the illuminator and the camera are exposed to the laser weld, the laser aperture of the end effector can for example expose another pole region of the stack of battery cells.

[0070] Still further in accordance with the eighth aspect of the present disclosure, the laser beam can for example be directed to the other pole region of the stack of battery cells simultaneously to said illuminating and said capturing.

[0071] Still further in accordance with the eighth aspect of the present disclosure, said illumination beam can for example be a uniform illumination beam.

[0072] Still further in accordance with the eighth aspect of the present disclosure, said illuminator can for example have a plurality of light-emitting diodes (LEDs).

[0073] Still further in accordance with the eighth aspect of the present disclosure, wherein the camera can for example be a high-resolution camera.

[0074] In accordance with a ninth aspect of the present disclosure, there is provided a laser welding system for inspecting laser welds connecting pole regions of a current collector to poles of a stack of battery cells, the current collector and battery cells received at a welding area with the pole regions located adjacent to and aligned with corresponding ones of the poles, the laser welding system comprising: a robot having an end effector having a body, a laser aperture extending across the body, an illuminator mounted to the body and spaced apart from the laser aperture, and a camera mounted to the body and spaced apart from the laser aperture, the robot moving the end effector within the welding area towards a given pole region of the current collector, said moving including exposing the given pole region via the laser aperture; a laser welder having an emitter emitting a laser beam, and a scanning head optically coupled to the laser emitter, the laser welder directing, via the scanning head, the laser beam across the laser aperture and forming a laser weld at the given pole region; the robot moving the body of the end effector away from the given pole region after said laser weld has been formed, said moving including exposing the laser weld to the illuminator and the camera; the illuminator projecting an illumination beam thereby illuminating the laser weld; and the camera capturing an image of the laser weld during said illuminating, the imageincluding the laser weld and surrounding given pole region, the laser weld being inspectable based on the image.

[0075] Further in accordance with the ninth aspect of the present disclosure, the laser welding system can for example further comprise a controller communicatively coupled to the camera, the controller inspecting the laser weld based on the image.

[0076] Still further in accordance with the ninth aspect of the present disclosure, said inspecting can for example include outputting a laser weld status indicative of a status of the laser weld.

[0077] Still further in accordance with the ninth aspect of the present disclosure, the controller can for example have a processor, and a non-transitory computer memory having stored thereon instructions that when executed by the processor perform one or more steps of inspecting, said inspecting including identifying the laser weld in the image, determining the weld status based on the identified laser weld in the image, and instructing the laser welder to correct said laser weld when the determined weld status requires correction.

[0078] Still further in accordance with the ninth aspect of the present disclosure, the end effector can for example have an arm protruding from the body of the end effector, said illuminator and said camera mounted to the arm.

[0079] Still further in accordance with the ninth aspect of the present disclosure, the illuminator can for example surround the camera.

[0080] Still further in accordance with the ninth aspect of the present disclosure, when the body of the end effector has been moved away from the given pole region, a field of view of the camera and the illumination beam of the illuminator can for example be directed towards the laser weld along a vertical orientation.

[0081] Still further in accordance with the ninth aspect of the present disclosure, said end effector can for example have a pressing element mounted to the body, said moving the end effector within the welding area towards the given pole region of the current including thepressing element applying a pressure to a periphery of the given pole region, thereby forcing the given pole region against a corresponding one of the poles.

[0082] Still further in accordance with the ninth aspect of the present disclosure, the illuminator can for example have a plurality of light-emitting diodes (LEDs).

[0083] Still further in accordance with the ninth aspect of the present disclosure, the camera can for example be a high-resolution camera.

[0084] All technical implementation details and advantages described with respect to a particular aspect of the present invention are self-evidently mutatis mutandis applicable for all other aspects of the present invention.

[0085] Many further features and combinations thereof concerning the present improvements will appear to those skilled in the art following a reading of the instant disclosure.DESCRIPTION OF THE FIGURES

[0086] In the figures,

[0087] Fig. 1 is an oblique view of examples of current collectors for a cylindrical battery cell and for a prismatic battery cell, in accordance with the prior art;

[0088] Fig. 1 A is a sectional view of the current collector of the cylindrical battery cell of Fig. 1 , taken along section 1A-1A, showing an underlying battery module, in accordance with the prior art;

[0089] Fig. 1 B is a top view of a portion of the current collector of Fig. 1 , showing the underlying battery module and weld lines, in accordance with the prior art;

[0090] Fig. 2A is a schematic view of an example of a laser welding system for inspecting laser welds connecting a current collector to a battery module, showing a robot carrying an end effector, a laser welder, an illuminator, a camera and a controller, in accordance with one or more embodiments;

[0091] Fig. 2B is a schematic view of the laser welding system of Fig. 2A, showing illumination and image capture of a laser weld through a laser aperture of the end effector, in accordance with one or more embodiments;

[0092] Fig. 3 is an enlarged, side elevation view of a laser welding system for inspecting laser welds connecting a current collector to a battery module, showing an illumination beam and a camera’s field of view encompassing laser apertures of an end effector, in accordance with one or more embodiments;

[0093] Fig. 3A is a top view of given pole regions of Fig. 3, superposed with desired weld line areas, in accordance with one or more embodiments;

[0094] Fig. 3B is an image of weld lines made to the given pole regions of Fig. 3A immediately after laser welding, in accordance with one or more embodiments;

[0095] Fig. 4 is a top view of an example of a laser welding system for inspecting laser welds connecting a current collector to a battery module, shown with four different robots moving respective end effectors relative to the battery module, in accordance with one or more embodiments;

[0096] Fig. 5 is a graph showing states for the laser welding system of Fig. 4 during concurrent welding sequences, in accordance with one or more embodiments;

[0097] Fig. 6 is a side elevation view of an example of an end effector having a retractable reflector assembly, in accordance with one or more embodiments;

[0098] Fig. 6A is a front view of an example of an illuminator of the end effector of Fig. 6, taken along view 6A-6A of Fig. 6, in accordance with one or more embodiments;

[0099] Fig. 7 is a flow chart of an example method for inspecting laser welds, in accordance with one or more embodiments;

[0100] Fig. 8 is a schematic view of an example of a computing device of a controller of a laser welding system of Figs 2A-2B, in accordance with one or more embodiments;

[0101] Fig. 9 is a schematic view of an example of some modules of the controller of Fig. 8, in accordance with one or more embodiments;

[0102] Fig. 10 is an enlarged, side elevation view of a laser welding system for inspecting laser welds connecting a current collector to a battery module, showing first and second effectors applying pressure around the pole region of a respective battery cell, in accordance with one or more embodiments;

[0103] Fig. 11A is an oblique view of another example of a laser welding system for inspecting laser welds connecting a current collector to a battery module, showing an end effector to which are mounted an illuminator and a camera mounted to an end effector, in accordance with one or more embodiments;

[0104] Fig. 11 B is a top plan view of the laser welding system of Fig. 11A, in accordance with one or more embodiments; and

[0105] Fig. 12 is a flow chart of another example of a method for inspecting laser welds, in accordance with one or more embodiments.DETAILED DESCRIPTION

[0106] Figs. 2A and 2B show an example of a laser welding system 100, in accordance with an embodiment. More specifically, the laser welding system 100 can be used for successively welding pole regions 102 of a current collector 104 to poles 106 of a stack of battery cells 108. Generally, the current collector 104 and the battery cells 108 are received at a welding area 110 with the pole regions 102 located adjacent to and aligned with corresponding ones of the poles 106. As discussed below, the laser welding system 100 can be used for inspecting laser weld(s) connecting the pole regions to the corresponding poles. It is intended that the inspection of the laser weld(s) can reveal that some of the pole regions are fully connected, only partially connected, or not connected at all, to the corresponding poles. The inspection can thus lead to further corrective laser welding steps, as discussed below in greater details.

[0107] As depicted, the laser welding system 100 has a robot 112, an illuminator 114, a camera 116, and a laser welder 118. During use, the robot 112 moves an end effector 120 within the welding area 110 towards one or more given pole region(s) 102 of the currentcollector 104. The given pole region(s) 102 can correspond to a positive pole region, a negative pole region, or both depending on the embodiment. As shown, the end effector 120 has a body 122, and a laser aperture 124 extending across the body 122. The end effector 120 can thus be moved in a manner exposing the given pole region 102 via the laser aperture 124. Moreover, in some embodiments, the end effector 120 can have a pressing element mounted to the body 122 which can be moved to apply a pressure to a periphery of the given pole region 102, effectively pressing the given pole region 102 against the underlying corresponding pole 106. Referring now more specifically to Fig. 2A, a scanning head 128 of the laser welder 118 directs a laser beam 130 across the laser aperture 124 to laser weld the given pole region 102 to the corresponding pole 106 thereby forming a laser weld (not shown in this figure). Referring now to Fig. 2B, the illuminator 114 projects an illumination beam 126 through the laser aperture 124 thereby illuminating the laser weld and the surrounding given pole region 102. During the illumination of the given pole region 102, the camera 116 captures an image of the laser aperture 124 including at least the laser weld. Preferably, the illumination and image capture are performed shortly after the laser welding. For instance, the image may be captured within 30 ms of the laser welding, preferably within 20 ms of the laser welding and most preferably within 10 ms or below of the laser welding. The laser beam 130 can be directed within the laser aperture 124 based on previously acquired coordinates, for instance. Indeed, it is intended that as the image shows a properly illuminated area, a controller 132 can inspect, using conventional or machine learning image recognition techniques, the laser weld based on the image and output a weld status indicative of a status (e.g., quality) of the corresponding laser weld. In situations where the laser weld is deemed satisfactory, no further laser welding action may ensue. In some embodiments, the satisfactory weld status can be stored on an accessible memory, along with the coordinates of the satisfactory laser weld in the battery module. However, when a status of the laser weld requires correction, the controller 132 can instruct the laser welder to correct the laser weld, thereby making sure that all or almost all of the laser welds of the battery module are of satisfactory quality on a consistent basis. In some embodiments, the inspection step may be performed immediately after the laser weld has been formed, as soon as the image is accessible for inspection and while the end effector still expose the given pole region to the laser welder. In these embodiments, any defective laser weld may be corrected on-the-go. In some other embodiments, shortly after the image capture, the end effector is moved on to another pole region for its correspondinglaser welding. It is only after a given image processing time has elapsed that a laser weld status can be determined. In these latter embodiments, the end effector can be moved back to the given pole region, thereby exposing the defective laser weld back to the laser welder and enabling the necessary corrections to be made.

[0108] In the illustrated embodiment, the robot 112 has a base end 112a which is fixedly mounted to a base 132 (e.g., floor, table), and a distal end 112b to which is mounted the end effector 120. Typically, the robot 112 is a three-axis robot capable of movement within the welding area 110 along the three axes x, y and z. In some embodiments, the robot 112 can be a SCARA robot or any other suitable robot. Although only one robot is shown in Figs. 2A and 2B, it is intended that the laser welding system 100 can include two, three, four or more different robots independently operated, with each robot moving its own, dedicated end effector. In this way, while the laser welder 118 is directing the laser beam 130 across the laser aperture 124 of the end effector 120 of one of the robots, the other robots can be moving their own end effectors towards a pole region to laser weld in preparation for a subsequent laser welding operation. In some embodiments, the step of inspecting the laser weld based on the image can be performed simultaneously to the steps of laser welding another pole region to form another laser weld, illuminating the other laser weld and capturing an image thereof, thereby maximizing the efficiency of the overall laser welding system 100.

[0109] As shown, the laser welder 118 can be suspended above the welding area 110 by a gantry system 134 capable of moving the laser welder 118 at least along the two axes x and y. As such, during use, the laser welder 118 can be moved slowly over the stack of battery cells 108 while the robot(s) 112 are moved quickly from one pole region 102 to another. The illuminator 114 and the camera 116 can be provided in the form of an imaging assembly mounted to the gantry system 134. In this specific embodiment, the imaging assembly is indirectly mounted to the gantry system 134 via the laser welder 118, as shown in Figs. 2A and 2B. More specifically, in this specific example, the illumination beam 126 and the field of view 136 of the camera 116 are directed towards the given pole region 102 via the scanning head 128 of the laser welder 118. In some other embodiments, the laser welding system 100 can have an independent frame dedicated to the imaging assembly. In these embodiments, the imaging assembly may have a dedicated frame (independent from the frame of the gantrysystem or a frame of the laser welder, for instance) to which the illuminator 114 and the camera 116 are mounted.

[0110] The controller 132 can be communicatively coupled to the robot 112, the illuminator 114, the camera 116, the laser welder 118, and / or the gantry system 134, depending on the embodiment. Although the controller 132 is shown as a standalone and remote device in this embodiment, it is intended that the controller 132 can include a number of interconnected individual controllers including, but not limited to, a robot controller, a laser welder controller and the like. As will be discussed in greater detail below, the controller 132 can have weld status determinator configured for identifying the laser weld in the image and determining the weld status indicative of a quality of the laser weld. The statuses can include, but are not limited to, defective, satisfactory, pass, fail, to name a few examples. In embodiments where the illumination beam 126 provides uniform illumination, the weld status determinator can be trained using a set of training images showing uniformly illuminated laser welds (e.g., laser weld lines) annotated with corresponding weld statuses, for instance.

[0111] Additionally or alternately, the controller 132 can include a weld defect locator, another module distinct and independent from the weld status determinator. During use, the weld defect locator can, for each weld status being deemed defective, determining corrective weld coordinates indicative of where the laser beam should be directed to render the corresponding laser weld satisfactory. The corrective weld coordinates can be outputted in the form of point coordinates (e.g., two-dimension coordinates (xi, yi), or three-dimension coordinates (xi, yi, zi)) representing a path of the spot of the laser beam for each one of a plurality of required corrective welds.

[0112] In some other aspects, the controller can include a weld coordinate locator in embodiments where the illumination and image capture are performed before the laser welding. In these embodiments, the weld coordinate locator is configured for identifying a representation of the given pole region in the image, and determining weld line coordinates in the image. Once the weld line coordinates are determined, the controller can control the laser welder to laser weld the given pole region to the underlying pole in an efficient and consistent manner. In embodiments where the illumination beam provides uniform illumination, the weldcoordinate locator can be trained using a set of training images showing uniformly illuminated pole regions annotated with proper weld line coordinates, for instance.

[0113] Referring now to Fig. 3, the battery cells 208 to be laser welded are of a type having both positive and negative poles 206a and 206b exposed on a top pole end thereof. More specifically, the current collector 204 has, for each underlying battery cell 208, a positive pole region 202a adjacent to and aligned with a corresponding positive pole 206a, and a negative pole region 202b adjacent to and aligned with a corresponding negative pole 206b. In this embodiment, the end effector 220 has a body 222, and laser apertures 224a and 224b extending across the body 222. As such, the laser apertures 224a and 224b include a first aperture 224a exposing the positive pole region 202a and a second aperture 224b exposing the negative pole region 202b when the end effector 220 is appropriately positioned within the welding area 210. In other embodiments, the end effector can be provided with a single laser aperture, for instance in situations where the battery cells have pole ends exposing only a single pole. In other words, when the robot moves the body 222 of the end effector 220 within the welding area 210 towards positive and negative pole regions 202a and 202b of the current collector 204, the positive and negative pole regions 206a and 206b are exposed to the laser welder via the first and second laser apertures 224a and 224b, respectively. The end effector 220 may be translated and / or rotated to accommodate the orientation of the positive and negative pole regions 202a and 202b of the current collector 204.

[0114] As depicted in this embodiment, the camera is optically coupled to the scanning head of the laser welder. Accordingly, the field of view 236 of the camera roughly corresponds to the field of view of the laser welder (referring to herein as “the welding area 210”). The illuminator 214 is directly mounted to the body 222 of the end effector 220 in this embodiment. As shown, the illumination beam 226 projected by the illuminator 214 reaches the given pole regions 202a and 202b via the first and second laser apertures 224a and 224b. The projection is made at an angle which allows proper illumination of the given pole regions 202a and 202b whenever they are exposed through the first and second laser apertures 224a and 224b of the end effector 220. More importantly, the position of the illuminator 214 relative to the body 222 of the end effector 220 is constant from one laser welding step to another, always cleared from a laser beam path. As such, the illumination of the given pole regions 202a and 202bduring the image capture is constant and uniform thereby providing images with similar illumination conditions consistently. As depicted, it was found preferable to provide the first and second laser apertures 224a and 224b with tapering walls in order to allow a broader range of angles of the illumination beam 226.

[0115] In some embodiments, the end effector 220 has a pressing element 240 mounted to the body 220. The pressing element 240 can be used to apply a pressure to a periphery of the positive and negative pole regions 202a and 202b of the current collector 204 against corresponding ones of positive and negative poles 206a and 206b. An example of such a pressure-and-weld system and method is described in International Patent Application filing no. PCT / CA2023 / 050492, the contents of which are hereby incorporated by reference. However, other pressure-and-weld systems and methods can be used in some other embodiments. As such, in these embodiments, the illumination of the pole regions 202a and 202b and the image capture are both performed during the application of the pressure P by the pressing element 240.

[0116] Fig. 3A shows an example of a top view showing the body 222, the laser apertures 224a and 224b and pole regions 202a and 202b. Weld line areas 242a and 242b have been superposed to the figure in a manner circumscribing the positive and negative pole regions 206a and 206b. The weld line coordinates can be any suitable coordinates circumscribed within the weld line areas 342a and 342b, for instance. Fig. 3B shows an image 300 showing representations of the positive and negative pole regions 202a’ and 202b’ laser welded with respective weld lines 244a’ and 244b’. As depicted, the image 300 shows a representation of the body 222’ of the end effector along with representations of the first and second laser apertures 224a’ and 224b’. The image 300 can have a resolution above 1 megapixel, preferably above 8 megapixels, and most preferably at least 20 megapixels. Moreover, the camera can have a camera objective having a 1x zoom, preferably a 4x zoom and most preferably a 10x zoom. In some embodiments, the camera can be equipped with an ultra- wide-angle lens and the like.

[0117] Referring now to Fig. 4, there is shown an example of a laser welding system 400 including four different and mechanically independent robots 412, each having a robot arm with a dedicated end effector 420. As shown, the triangular-like shape of the end effectors 420can provide at least some clearance thereby allowing greater movement possibilities for each of the end effectors 420. The four end effectors 420 are attached to the second ends of the robots 412 using a cantilevered member. The cantilevered members can help clearing the field of view of the scanning head from parts of the robot arms that could obstruct it. In this example, each of the robot arms has its first end fixed to a base located on a respective side of the battery module, with its second end being movable above the pack of battery cells 408 within the field of view 410 of the laser welding system. By using multiple robot arms 422, the time required to laser weld all of the pole regions of the current collector to corresponding poles of the battery cells 408 can be significantly reduced.

[0118] Fig. 5 shows a graph 500 showing the states of the laser welding system 400 and of the robot states during consecutive welding sequences. As shown, each of the robots is performing a similar welding sequence but delayed from one another. Accordingly, this can allow the laser beam of the laser welding system 400 to be activated four times as much during a single welding sequence, which can reduce the amount of time required to laser weld all the battery cells 408 of a module. In some embodiments, only one first robot can be sufficient. In some other embodiments, two or more first robots can be used to proportionally optimize the laser welding sequences and overall throughput. Experiments conducted using the laser welding system 400 of Fig. 4 shows that the time required to move an end effector 420 from one pole region to another pole region is at least about 300 ms while the time required to laser weld the two weld lines is at least about 40 ms (20 ms per pole, for two poles). As such, if one were to use the four robots 412 simultaneously, but in delayed and concurrent fashion with respect to one another such as shown in Fig. 5, there can be four laser weld activations lasting for a total of about 160 ms. However, since the time required to move the robots to subsequent positions lasts 300 ms, the laser welder remains off for about 140 ms in the whole welding sequence. Fig. 5 shows an example of how such an optimized sequence can be performed without necessarily slowing the broader laser welding operation. As shown in Fig. 5, it is intended that while the first robot 412 is moving the end effector 420 towards a first pole region, the illumination, image capture and laser welding can be performed by the second, third and fourth robots for other pole regions in a concurrent manner.

[0119] Fig. 6 shows an example of a robot 612 and corresponding end effector 620. As shown, the end effector 620 has a first end 620a mounted to the robot 612 and a second end 620b opposite the first end 620a. The laser aperture 624 is positioned between the first and second ends 620a and 620b. In this specific embodiment, the imaging assembly 633, i.e., incorporating the illuminator 614 and the camera 616, is mounted to the body 622 of the end effector 620. As the illumination beam 626 and the field of view 636 of the camera 616 are directed in a parallel manner along the body 622 of the end effector 620 for at least a given distance, a retractable reflector assembly 650 is provided to redirect the illumination beam 626 and the field of view 636 towards a given pole region via the laser aperture 624. More specifically, the retractable reflector assembly 650 has a reflector element 652 movable between a use position, in which the reflector element 652 directs the illumination beam 626 and the camera’s field of view 636 across the laser aperture 624 towards a potential laser weld, and a retracted position, in which the reflector element 652 is cleared from a laser beam path 654. In these specific embodiments, the retractable reflector assembly 650 can be moved from the use position to the retracted position repeatedly in a coordinated manner preventing physical interference between the laser welding step and the illuminating and imaging steps. Shortly before the laser welding step begins, the reflector element 652 is moved in the retracted position. Immediately after the laser welding step has ended, the reflector element 652 can be moved in the use position thereby allowing illumination and image capture of the laser weld.

[0120] In this specific embodiment, and as shown in Fig. 6A, the illuminator 614 can be provided in the form of a series of LEDs 668 annularly distributed around a field of view or objective of the camera 616. The number of LEDs can differ from one embodiment to another. For instance, the series of LEDs 668 can include fewer than eight LEDs 668, or more than eight LEDs 668. Although the illuminator 614 and the camera 616 are both mounted to the end effector 620 in the depicted embodiment, it is envisaged that the illuminator may be mounted to the laser welder, or to a gantry system holding the laser welder, while the camera can be mounted to the end effector, or vice versa.

[0121] In some other embodiments, the retractable reflector assembly 650 can be omitted even if the imaging assembly is directly or indirectly mounted to the end effector 620. Indeed,in these embodiments, the illuminator and camera can be suspended substantially above the laser aperture(s) of the end effector 620 while clearing the laser beam path 654 at all times during the pressure application. In these embodiments, the illumination beam 626 and the camera’s field of view 636 can have an impending angle shaving an angle of tapering walls of the laser aperture 624, for instance.

[0122] Fig. 7 shows an example of a method 700 for inspecting laser welds connecting pole regions of a current collector to poles of a stack of battery cells. As discussed above, the welding can be performed with a laser beam when the current collector and battery cells are received at a welding area with the pole regions located adjacent to and aligned with corresponding ones of the poles. The laser beam can be generated by a laser welder positioned above the welding area.

[0123] At step 702, a robot moves an end effector within the welding area towards a given pole region of the current collector. As discussed above, the end effector generally has a body, and a laser aperture extending across the body. The step 702 includes the movement of the end effector until the given pole region is exposed to the laser welder via the laser aperture. In some embodiments, and as per step 702a, the robot moves, e.g., a pressing element of the end effector, to press a periphery of the given pole region of the current collector against a corresponding one of the poles.

[0124] At step 704, a scanning head of the laser welder directs the laser beam across the laser aperture thereby forming a laser weld at the given pole region. In some embodiments, the laser source is pulsed and the beam is a pulsed laser welding beam. In some other embodiments, the laser source is continuous wave (CW) so the laser welding beam a CW laser welding beam. A source collimating lens can be optically coupled to the laser source to collimate the laser welding beam along the beam path as it exits the laser source. In this example, the laser welder has a scanning head including a pair of reflective surfaces which can redirect the laser welding beam in the x and y plane as desired. The pair of reflective surfaces can be provided in the form of galvo scan mirrors in some embodiments. The scanning head generally defines the working area and corresponding field of view of the laser welder as the working area is generally circumscribed by the maximal x and y movements of the laser welding beam in the x and y plane. The size of the working area generally furtherdepends on a distance separating the scanning head and the current collector. Accordingly, for similar x and y movements of the laser welding beam, a greater distance between the laser welder and the current collector results in a larger working area, or vice versa. In some embodiments, the laser scanning head can be a Raylase Axial Scan Fiber 30 or Raylaser Axial Scan Fiber 50 scanning head. In this specific configuration, the laser welder has a prefocused configuration. Accordingly, a pre-focusing module including at least two focusing lenses, including at least one movable along the beam path, is provided between the laser source and the scanning head to adjust the focusing of the laser welding beam by moving a focal point of the laser welding beam along the beam path. In the f-theta lens configuration, the pre-focusing module can be omitted as an f-theta lens is instead positioned downstream of the scanning head to perform a similar focusing function.

[0125] At step 706, an illuminator projects an illumination beam through the laser aperture thereby illuminating the laser weld and its immediate surroundings for at least a given illumination time period. In some embodiments, the illumination beam can a uniform illumination beam. Additionally or alternatively, the illumination beam can be a diffuse illumination beam. The illuminator can be any suitable type of illuminator including, but not limited to, lamp(s) (e.g., white lamp(s)), light-emitting diode(s), infrared lamp(s), fiber-based illuminator(s), light projector(s), with different brightness levels ranging between 1 lumen and 10,000 lumens, for instance. In some embodiments, the illuminator is provided in the form of an array of LEDs. In any way, the brightness level of the illumination beam is substantially greater than a brightness level of the ambient illumination. The array can be linearly or arcuately-shaped depending on the embodiment. It is understood that although the illumination beam is projected across the laser aperture in this embodiment, the illumination beam may not be projected across the laser aperture in all intended embodiments.

[0126] At step 708, a camera captures one or more image(s) of the laser aperture including the laser weld and its surroundings at any point in time during the given illumination time period. The laser weld is inspectable based on the image. The camera can be any suitable type of camera including, but not limited to, high-resolution camera(s), visible light camera(s), infrared light camera(s) especially in situations where the illumination is an infrared illuminator, stereoscopic camera(s), single-lens reflex camera(s), point-and-shoot camera(s), digitalcamera(s), movie camera(s), mirrorless camera(s), smartphone camera(s), plenoptic camera(s), to name a few examples. In embodiments where the illuminator includes an array of LEDs, it is intended that the array of LEDs can be annularly arranged around a field of view of the camera. In these embodiments, the LEDs face in a direction similar to a direction of the field of view of the camera, thereby illuminating the field of view of the camera when activated. In some embodiments, the illumination beam and camera’s field of view can be redirected towards the given pole region via the scanning head of the laser welder regardless of its configuration, depending on the embodiment. It is intended that the steps 706 and 708 are performed as soon as the step 704 has been performed, and preferably shortly after weld fumes have cleared (using active or passive fume managing mechanisms) the field of view of the camera. For instance, the step 708 can be performed within 30 ms after step 704, preferably within 20 ms after step 704 and most preferably within 10 ms after step 704. In some embodiments, the steps 704, 706 and 708 are performed during the step 702a. In other words, the illumination of the laser weld and its image capture are performed simultaneously to the pressing of the periphery of the given pole region against the underlying pole. The end effector can thus be maintained into an engaged position during the laser welding, the illumination and image capture. It is intended that although the image is captured across the laser aperture in this embodiment, the image may not be projected across the laser aperture in all intended embodiments.

[0127] At optional step 710, the laser weld is inspected based on the captured image(s). It is understood that the step of inspecting is optional as it can be done at a remote location, or at a later time, depending on the embodiment. In certain embodiments, a laser weld status indicative of a status of the laser weld can even be outputted. In this step, a controller can access the captured image(s), identify the laser weld(s) therein, and determining a weld status associated to each of the laser weld(s). When corrections are required, the controller can instruct the laser welder to perform a corrective laser welding step to the laser welds having unsatisfactory weld statuses. The corrective laser welding step can be performed immediately after said step 710 has been performed, or only after other or all of the pole regions of the current collector have been laser welded to corresponding poles. In this latter situation, it is encompassed that the corrective laser welding step(s), if any, can be performed before thebattery module is moved away from the welding area. In this manner, extra manipulation of the battery module can be avoided to optimize the overall laser welding process.

[0128] Referring now to Fig. 8, the controller can be provided as a combination of hardware and software components. Broadly described, the controller can be communicatively coupled to the robot, the illuminator, the camera, the laser welder (and its scanning head), or a combination thereof. The communicative coupling can be wired or wireless or a combination of both, depending on the embodiment. It is intended that the controller has one or more processor(s), and one or more non-transitory computer-readable memory(ies) having stored thereon instructions that when executed by the processor(s) performs some predetermined steps. More specifically, the hardware components can be implemented in the form of a computing device 800, an example of which is described with reference to Fig. 8. The computing device 800 can have a processor 802, a memory 804, and I / O interface 806. Instructions 808 for controlling the laser welding sequences can be stored on the memory 804 and accessible by the processor 802.

[0129] The processor 802 can be, for example, a general-purpose microprocessor or microcontroller, a digital signal processing (DSP) processor, an integrated circuit, a field- programmable gate array (FPGA), a reconfigurable processor, a programmable read-only memory (PROM), a programmable logic controller (PLC), or any combination thereof.

[0130] The memory 804 can include a suitable combination of any type of computer- readable memory that is located either internally or externally such as, for example, randomaccess memory (RAM), read-only memory (ROM), compact disc read-only memory (CDROM), electro-optical memory, magneto-optical memory, erasable programmable readonly memory (EPROM), and electrically-erasable programmable read-only memory (EEPROM), Ferroelectric RAM (FRAM) or the like.

[0131] Each I / O interface 806 enables the computing device 800 to interconnect with one or more input devices, such as keyboard(s), sensor(s), or with one or more output devices such as display(s), accessible memory(ies), robot(s), illuminator(s), camera(s) and laser welder(s).

[0132] Each I / O interface 806 enables the controller to communicate with other components, to exchange data with other components, to access and connect to network resources, to server applications, and perform other computing applications by connecting to a network (or multiple networks) capable of carrying data including the Internet, Ethernet, plain old telephone service (POTS) line, public switch telephone network (PSTN), integrated services digital network (ISDN), digital subscriber line (DSL), coaxial cable, fibre optics, satellite, mobile, wireless (e.g., Wi-Fi, WiMAX), SS7 signaling network, fixed line, local area network, wide area network, and others, including any combination of these.

[0133] The computing device 800 and any software application that can be run by the computing device 800 are meant to be examples only. Other suitable embodiments of the controller can also be provided, as it will be apparent to the skilled reader.

[0134] The controller can include a number of modules each provided as a combination of hardware and software components. Fig. 9 shows an example module embodying a weld status determinator 900, in accordance with one embodiment. As shown, the weld status determinator 900 can be stored on a memory of the controller, or any other accessible memory or server, and executable to perform a number of functions. For instance, the weld status determinator 900 can be used to access the captured image(s) 902, identify the laser weld(s) in the accessed image(s) 902, and to determine weld status(es) 904 from the accessed image(s) 902. The weld status(es) 904 can be indicative of whether the laser welds are deemed satisfactory. For instance, weld statuses can include, but are not limited to, defective, satisfactory, pass, fail and the like. Corrective weld coordinates of the laser weld failures can be determined by a weld defect locator 910, another module of the controller. In this embodiment, the corrective weld coordinates 912 can be registered in a system coordinate common to the laser welder, or in a system coordinate common to any other component of the laser welding system. The controller can thereby, based on the corrective weld coordinates 912, direct the laser beam of the laser welder at appropriate locations to perform corrective welds at satisfactory locations, orientations, depths and the like. In some embodiments, the corrective weld coordinates 912 include coordinates for at least two welds: one for a corrective welding of the positive electrical contact and another one for a corrective welding of the negative electrical contact.

[0135] In some embodiments, the weld status determinator 900 and / or the weld defect locator 910 can be trained using machine learning / artificial intelligence based on corresponding sets of training images annotated with corresponding weld status(es) and / or defect coordinates. It is intended that the sets of training images have been captured using a focus and / or illuminating conditions similar to those provided by the illuminator described herein. As such, the computational processing steps performed by the weld status determinator and the weld defect locator 910 in real time or quasi-real time are facilitated as the image(s) captured by the camera during the laser welding operations are similar in shape, size, and / or illuminating conditions than those of the training images. It is encompassed that the sets of training images can be selected based on a given type 906 of battery cell. As such, the training of the weld status determinator 900 and / or weld defect locator 910 can be performed one or more different battery types including, but not limited to, cylindrical battery cell formats 21700, 18650 and 4680, other types of cylindrical battery cells, battery cells of any other suitable shapes such as prismatic battery cells, to name only a few examples.

[0136] For instance, in some embodiments, the the weld status determinator 900 and / or the weld defect locator 910 can be trained using supervised learning. Supervised machine learning engines can be based on Artificial Neural Networks (ANN), Support Vector Machines (SVM), capsule-based networks, Linear Discriminant Analysis (LDA), classification tree, a combination thereof, and any other suitable supervised machine learning engine. However, as can be understood, in some other embodiments, it is intended that the weld status determinator 900 and / or the weld defect locator 910 can be trained using unsupervised learning. For instance, unsupervised clustering algorithms can be used. Two exemplary methods for improving classifier performance include boosting and bagging which involve using several classifiers together to “vote” for a final decision. Combination rules can include voting, decision trees, and linear and nonlinear combinations of classifier outputs. These approaches can also provide the ability to control the tradeoff between precision and accuracy through changes in weights or thresholds. These methods can lend themselves to extension to large numbers of localized features. In any case, some of these engines may require human interaction during training, or to initiate the engine, however human interaction may not be required while the engine is being carried out, e.g., during analysis of an accessed image. SeeNasrabadi, Nasser M. "Pattern recognition and machine learning." Journal of electronic imaging 16.4 (2007): 049901 for further detail concerning such trained engines.

[0137] In another aspect, a first end effector can apply pressure around a first pole region while the laser welding step is performed whereas a second end effector can apply pressure around a second pole region while the illumination and image capture steps are performed independently from the laser welding step. Fig. 10 shows a system 1000 similar to the system 100 of Fig. 1 , but with two different and independently manipulated end effectors. As depicted, the system 1000 has a first end effector 1020a which applies pressure around the pole regions of a second battery cell 1008b. Then, the laser beam 1030 can be directed through the first apertures 1024a of the first end effector 1020a to laser weld the pole region exposed therethrough. The first end effector 1020a can be moved by a first robot and the second end effector 1020b can be moved by a second robot independent from the first robot. In this particular embodiment, the first end effector 1020a has first laser welded the pole regions of the first battery cell 1008a and was then moved to the pole regions of the second battery cell 1008b using the first robot for instance. As depicted, once the pole regions of the first battery cell 1008a have been laser welded (through the first apertures 1024a of the first end effector 1020a), a second end effector 1020b is moved to apply pressure around the pole regions of the first battery cell 1008a so that illumination and image capture can be performed through the second apertures 1024b of the second end effector 1020b, thereby allowing weld statuses to be determined. The first and second end effectors 1020a and 1020b can be used in series such that they are moved along a similar path within the stack of battery cells, only delayed from one another. In some embodiments, the delay can correspond to the laser-welding step of one battery cell, or more depending on the embodiment.

[0138] In this way, each of the first and second end effectors 1020a and 1020b can have a dedicated function, namely a function of assisting in the laser welding step (for the first end effector 1020a) and / or a function of assisting in the illumination and image capture steps (for the second end effector 1020b). Since these functions are different in purpose, the first and second end effectors 1020a and 1020b can be different in construction and still achieve their purpose in a satisfactory manner. More specifically, in the depicted embodiment, both the illuminator 1014 and the camera 1016 are mounted to the second end effector 1020b. Forinstance, in this specific embodiment, the illuminator 1014 and the camera 1016 are mounted to a cantilever arm suspended above the second apertures 1024b. As shown, the field of view of the camera 1016 and the illumination beam of the illuminator 1014 are both directed towards the second apertures 1024b along the vertical orientation z. In other words, the camera 1016 and the illuminator 1014 are oriented vertically above the second apertures 1024b. In this embodiment, there is no need to have the camera’s field of view or the illumination beam impinging at an angle relative to the second apertures 1024b since the second end effector 1024b is not involved in the laser welding step. The illuminator 1014 and the camera 1016 are thus out of physical interference with the laser beam 1030 at all times in this embodiment.

[0139] The first and second end effectors and can be similar in construction and / or shape. In some embodiments, the laser welding step is solely performed through the first apertures of the first end effector whereas the illumination and image capture steps are solely performed through the second apertures of the second end effector, or vice versa. In some other embodiments, the laser welding step can be performed through either the first apertures of the first end effector or the second apertures of the second end effector. Additionally, the illumination and image capture steps can be performed through either the first apertures of the first end effector or the second apertures of the second end effector, depending on the embodiment. It is intended that the step of moving the first end effector away from a welded pole region is made without physical interference with the step of moving the second end effector towards the given pole region. In some embodiments, the second end effector can be kept away from the welding area. In some other embodiments, the second end effector moves within the welding area, but is kept away from the laser beam and its immediate surroundings.

[0140] Figs. 11 A and 11 B show another example of a portion of a laser welding system for inspecting laser welds connecting a current collector to a battery module, in accordance with another embodiment. As depicted, the system 1100 has an end effector 1120 which is movable above the current collector and the battery module during use. The end effector 1120 has a body 1122 having a free end 1122a and a fixed end 1122b mounted to a robot (not shown). Laser apertures 1124 are provided across the free end of the body 1122 of the end effector 1120. In this embodiment, two laser apertures 1124 are sized and shaped to expose corresponding positive and negative pole regions of the current collector and some portionsof the underlying positive and negative electrical poles of the battery module. In some embodiments, pressing elements 1140 are positioned around the laser apertures 1124 to apply pressure around the corresponding pole regions to firmly laser weld them to the underlying electrical poles during use. As illustrated, an illuminator 1114 is mounted to the body 1122 of the end effector 1120. Still in this embodiment, a camera 1116 is mounted to the body 1122 of the end effector 1120. More specifically, the illuminator 1114 surrounds the camera in this specific embodiment. The illuminator 1114 and the camera 1116 are both mounted to an arm 1123 protruding from the body 1122 of the end effector 1120. As such, the illuminator 1114 and the camera 1116 clear a vertical projection of the laser apertures 1124 and are thereby located away from the laser beam during the laser welding step. In some other embodiments, the illuminator 1114 and the camera 1116 may be mounted to different arms protruding from the body 1122 of the end effector 1120. As a result, both the illuminator 1114 and the camera 1116 are spaced away from the laser apertures 1124 by a common distance D. In some other embodiments, the illuminator 1114 and the camera 1116 may not be vertically aligned with one another, while still being laterally (e.g., in a plane parallel to the current collector / battery module) spaced apart from the laser apertures 1124.

[0141] As can be understood, the laser welding system does not illuminate the given pole regions through the corresponding laser apertures 1124 nor does it capture the image of the laser welds across the corresponding laser apertures 1124. Rather, the robot moves the end effector 1120 so as to expose the pole regions of the current collector across the corresponding laser apertures 1124. Such a movement can include a rotation movement rotating the first end effector about an axis perpendicular to the welding area, a translation movement translating the first end effector along a plane parallel to the welding area, or a combination of both. Then, a scanning head of a laser welder (not shown) directs a laser beam across the laser apertures 1124 and forms laser welds at the pole regions. Once the laser welds have been made, the robot moves the body 1122 of the end effector 1120 laterally in a manner which exposes the laser welds to a field of illumination of the illuminator 1114 and to a field of view of the camera 1116. In some preferred embodiments, the illuminator 1114 and the camera 1116 are moved so as to be vertically aligned with the laser welds. In other words, when the body 1122 of the end effector 1120 has been moved away from the laser weld, a field of view of the camera 1116 and the illumination beam of the illuminator 1114 are directedtowards the laser weld along a vertical orientation. In that position, or in any other suitable position, the illuminator 1114 is operated to illuminate the laser welds, and the camera 1116 is operated to capture one or more images of the laser welds. Accordingly, the illumination and the image capture are not performed through the laser apertures 1124, but rather when the laser apertures 1124 have been moved laterally away from the fresh laser welds. It is intended that while the fresh laser welds are being illuminated by the illuminator 1114 and imaged by the camera 1116, the laser apertures 1124 may expose another set of pole regions to laser weld, which can be simultaneously or sequentially laser-welded. With such a configuration, time savings can arise when combining the dual functions of illuminating / imaging a first set of laser welds while laser-welding a neighbouring, second set of laser welds. As shown in this example, the laser apertures 1124 are separated from the illuminator 1114 and the camera 1116 by the distance D. In some embodiments, for instance, when the battery cells are of bigger size (e.g., prismatic battery cells), the distance D may correspond to the spacing between adjacent battery cells. As such, when some fresh laser welds are being illuminated and imaged, an immediately adjacent battery cell can have its pole regions laser welded through the laser apertures 1124 of the end effector 1120. Otherwise, the distance D may be long enough to encompass a number of adjacent battery cells when they are of smaller sizes (e.g., 21700 battery cells). Accordingly, newly welded laser welds may not be illuminated and imaged right away. In these embodiments, newly welded laser welds may be illuminated and imaged only when the end effector 1120 has been moved by a distance roughly corresponding to the distance D, which may imply that one or more other pairs of laser welds have been made, in the meantime. It is intended that the construction of the end effector 1120 can depend on the type of battery cells that are to be laser-welded. Indeed, the distance D extending between the illuminator / camera and the laser apertures 1124 can vary from one embodiment to another.

[0142] Fig. 12 shows an example of a method 1200 for inspecting laser welds connecting pole regions of a current collector to poles of a stack of battery cells. As discussed above, the welding can be performed with a laser beam when the current collector and battery cells are received at a welding area with the pole regions located adjacent to and aligned with corresponding ones of the poles. The laser beam can be generated by a laser welderpositioned above the welding area. The method can be performed by a laser welding system such as the one shown and described with reference to Figs. 11 A and 11 B.

[0143] At step 1202, a robot moves an end effector within the welding area towards a given pole region of the current collector. As the end effector has a body, and a laser aperture extending across the body, said step 1202 of moving causes the given pole region to be exposed via the laser aperture.

[0144] In some embodiments, at step 1202a, the step 1202 of moving includes a pressing element of the end effector pressing the given pole region against a corresponding one of the electrical poles.

[0145] At step 1204, a scanning head of a laser welder directs a laser beam across the laser aperture of the end effector and so forms a laser weld at the given pole region.

[0146] At step 1206, the same robot moves the body of the end effector away from the given pole region. The step 1206 of moving exposes the laser weld to an illuminator and a camera that are both mounted to the body of the end effector. As the illuminator and the camera are laterally spaced away from the laser aperture, the laser aperture is free from the fresh laser weld. In some embodiments, while the laser aperture is free from the fresh laser weld, the laser aperture is positioned so as to expose a new pole region, which can be laser welded simultaneously to the following steps.

[0147] At step 1208, the illuminator projects an illumination beam thereby illuminating the laser weld.

[0148] At step 1210, the camera captures an image during said step 1208 of illuminating. The image includes the laser weld and surrounding given pole region. It is understood that the laser weld is inspectable based on the image.

[0149] At another, yet optional step, a controller inspects the laser weld based on the image. It is understood that the step of inspecting is optional as it can be done at a remote location, or at a later time, depending on the embodiment. In some embodiments, a force detector measuring a given force applied by the end effector against a surrounding of the given poleregion is provided. In these embodiments, a force signal is generated. The force signal can be indicative of the given force during said step 1204 of directing, which enables the step of inspecting to be further based on the force signal. Additionally or alternately, a laser weld monitor (LWM) can be used. The LWM can receive return signal(s) from the given pole region during said step 1204 of directing. As such, LWM signal(s) indicative of the return signal(s) can be generated. As a result, the step of inspecting can be further based on the LWM signals. Depending on the embodiment, the return signal(s) pertain to a retro reflection signal, an infrared radiation signal, an ultraviolet radiation signals, or a combination thereof. It is intended that although the inspection of the image of the laser weld is informed by the force detector and the LWM in this embodiment, this can be applied to any other embodiment described herein.

[0150] As can be understood, the examples described above and illustrated are intended to be exemplary only. For instance, it is intended that the illuminator can be mounted to the end effector or suspended above the welding area, remote from the end effector. In this latter embodiment, the illuminator can be directly or indirectly mounted to the laser welder. Similarly, the camera can be mounted to the end effector or suspended above the welding area, remote from the end effector. Again, the camera can be directly or indirectly mounted to the laser welder or to the end effector or to another end effector. In some embodiments, the illumination would be mounted to the end effector, with the camera suspended above the welding area with either a direct or indirect mounting to the gantry system moving the laser welder, or to the laser welder itself. For instance, in some embodiments, the laser weld status may not be outputted only based on the captured image, but may additionally be based on other data points including, but not limited to, data from a laser welding monitor (LWM), and the like. The scope is indicated by the appended claims.

Claims

WHAT IS CLAIMED IS:

1. A method for inspecting laser welds connecting pole regions of a current collector to poles of a stack of battery cells, the current collector and battery cells received at a welding area with the pole regions located adjacent to and aligned with corresponding ones of the poles, the method comprising: using a first robot, moving a first end effector within the welding area towards a given pole region of the current collector, the first end effector having a body, and a laser aperture extending across the body, said moving the first end effector including exposing the given pole region via the laser aperture; using a scanning head of a laser welder, directing a laser beam across the laser aperture and forming a laser weld at the given pole region; using an illuminator, projecting an illumination beam for illuminating the laser weld; and using a camera, capturing an image of the laser weld during said illuminating, the image including the laser weld and surrounding given pole region, the laser weld being inspectable based on the image.

2. The method of claim 1 wherein the illuminator and the camera are mounted to a second end effector movable by a second robot independent from the first robot.

3. The method of claim 2 wherein the method further comprises: after said directing, the first robot moving the first end effector away from the given pole region; and prior to said projecting the illumination beam and said capturing the image, the second robot moving the second end effector towards the given pole region.

4. The method of claim 3 wherein said moving the first end effector away from the given pole region and said moving the second end effector towards the given pole region are performed simultaneously without physically interfering with one another.

5. The method of claim 1 wherein the illuminator and the camera are mounted to the body of the first end effector, the illuminator and the camera clearing a vertical projection of the laser aperture and located away from the laser beam during said directing.

6. The method of claim 5 wherein the method further comprises: after said directing and prior to said projecting the illumination beam and said capturing the image, the first robot moving the laser aperture away from the given pole region while exposing the illuminator and the camera to the laser weld.

7. The method of claim 6 wherein said exposing the illuminator and the camera to the laser weld includes at least one of: rotating the first end effector about an axis perpendicular to the welding area and translating the first end effector along a plane parallel to the welding area.

8. The method of claim 1 wherein said first end effector has a pressing element mounted to the body, said moving the first end effector including the pressing element pressing a periphery of the given pole region of the current collector against a corresponding one of the poles.

9. The method of claim 8 wherein at least one of said illuminating and said capturing is performed during said pressing.

10. The method of claim 1 wherein at least one of said illuminating and said capturing is performed through the laser aperture.11 . The method of claim 1 wherein at least one of said illuminating and said capturing is performed via the scanning head of the laser welder.

12. The method of claim 1 further comprising, using a processor of a computing device, inspecting the laser weld based on the image.

13. The method of claim 12 wherein said inspecting includes outputting a laser weld status indicative of a status of the laser weld.

14. The method of claim 12 further comprising, using a force detector, measuring a given force applied by the first end effector against a surrounding of the given pole region and generating a force signal indicative of the given force during said directing, said inspecting further based on the force signal.

15. The method of claim 12 further comprising, using a laser weld monitor (LWM) receiving one or more return signals from the given pole region during said directing, generating one or more LWM signals indicative of said one or more return signals, said inspecting further based on the one or more LWM signals.

16. The method of claim 13 wherein said outputting includes identifying the laser weld in the image, determining the weld status based on the identified laser weld in the image, and instructing the laser welder to perform a correction on said laser weld when the determined weld status requires correction.

17. The method of claim 12 wherein said inspecting is performed by executing at least one of: one or more trained artificial neural networks, one or more support vector machines, and one or more capsule-based networks.

18. A laser welding system for inspecting laser welds connecting pole regions of a current collector to poles of a stack of battery cells, the current collector and battery cells received at a welding area with the pole regions located adjacent to and aligned with corresponding ones of the poles, the laser welding system comprising: a first robot having a first end effector having a body, and a laser aperture extending across the body, the first robot moving the body of the first end effector within the welding area towards a given pole region of the current collector, said moving the first end effector including exposing the given pole region via the laser aperture; a laser welder having an emitter emitting a laser beam, and a scanning head optically coupled to the laser emitter, the laser welder directing, via the scanning head, the laser beam across the laser aperture and forming a laser weld at the given pole region;an illuminator projecting an illumination beam for illuminating the laser weld; and a camera capturing an image of the laser weld during said illuminating, the image including the laser weld and surrounding given pole region, the laser weld being inspectable based on the image.

19. The laser welding system of claim 18 further comprising a second robot independent from the first robot, the illuminator and the camera mounted to a second end effector movable by the second robot.

20. The laser welding system of claim 18 wherein the illuminator and the camera are mounted to the body of the first end effector, the illuminator and the camera clearing a vertical projection of the laser aperture and located away from the laser beam during said directing.

21. The laser welding system of claim 20 wherein said illuminator and said camera are mounted to the body of the first end effector via an arm protruding therefrom.

22. The laser welding system of claim 18 wherein said first end effector has a pressing element mounted to the body, said moving the first end effector including the pressing element applying a pressure to a periphery of the given pole region, thereby forcing the given pole region against a corresponding one of the poles.

23. The laser welding system of claim 18 wherein at least one of said illuminating and said capturing is performed through the laser aperture.

24. The laser welding system of claim 18 wherein at least one of said illuminating and said capturing the image is performed via the scanning head of the laser welder.

25. The laser welding system of claim 18 further comprising a controller communicatively coupled to the camera, the controller having a processor and a non-transitory computer memory having stored thereon instructions that when executed by the processor perform the step of: inspecting the laser weld based on the image.

26. The laser welding system of claim 25 wherein said inspecting includes outputting a laser weld status indicative of a status of the laser weld.

27. The laser welding system of claim 26 wherein said outputting including identifying the laser weld in the image, determining the weld status based on the identified laser weld in the image, and instructing the laser welder to correct said laser weld when the determined weld status requires correction.

28. The laser welding system of claim 25 wherein said inspecting is performed by executing at least one of: one or more trained artificial neural networks, one or more support vector machines, and one or more capsule-based networks.

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