Patent Description:
When metallic panels are welded on supporting structural elements, it is well known that this may cause deformations in the panels. For instance, such panels, which can be outside body panels of vehicles, are relatively thin. When subjected to the heat required for welding the panels to supporting structural elements located behind them, deformations are generated in the panels. Such deformations can generally be corrected manually, but this has a detrimental effect on the whole cost of the manufacturing process.

<CIT> and entitled "Method for Automatic Conducting of a Straightening Process" discloses a method for automatically conducting a straightening process for an object to be straightened, such as sheet metal, strips, sections, pipes, and particularly for wire-like or multiwire-like objects, using a straightening device or a levelling machine. The method uses at least one mangle roll which can be adjusted by an actuator. A process simulation model of a straightening process that is to be conducted, and a process simulation program are set up. The process simulation program directly gives "online" the settings of the adjustable mangle rolls. During the straightening process, changes in the product data, in particular in the material characteristics and/or in the dimensions of the objects to be straightened which influence the realization of the straightening process, are recorded. From these, data for setting the adjustable mangle rolls are also calculated, and signals are emitted for the automatic setting of the adjustable mangle rolls using the at least one actuator.

<CIT> and entitled "Production Workpiece Straightening System" describes a production system for simultaneously correcting multiple distortions in multiple extensions of an irregular workpiece, such as steering knuckles for automotive vehicles, within tolerance requirements. For each distortion, there is provided a gauge for determining direction and magnitude automatically employed to monitor corrective deflection beyond yield point under an electronic controller program that automatically initiates, controls, and terminates simultaneous corrective deflection in either or both of two planes at each of the multiple workpiece locations. The electronic controller program is adapted to vary with the relative as well as the individual distortions and to update the straightening program with the straightening experience data of each successive workpiece in order to approach an optimum of simultaneous single stroke corrective deflection of the multiple distortions in multiple planes within total workpiece tolerances.

Therefore, it would be desirable to provide an apparatus and/or a process to automate the straightening of welded workpieces.

Processes and systems for correcting deformations in metallic components comprising the features of the preambles of claims <NUM> and <NUM> are disclosed in <CIT>, <CIT>, and <CIT>.

It would thus be desirable to provide a novel apparatus and/or process for straightening welded workpieces, such as panels.

The embodiments described herein provide in one aspect an automated method with the features of claim <NUM> and in another aspect a system with the features of claim <NUM>.

For a better understanding of the embodiments described herein and to show more clearly how they may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings, which show at least one exemplary embodiment, and in which:.

It is well known in the manufacturing field, such as in the train manufacturing industry, that welding operations may induce deformations in metallic components (e.g. components made of aluminum, steel, etc.). For example, welding external sub-assemblies of a shell of a rail vehicle, such as panels, to its underlying car body structure subjects those panels to deformations. These deformations need to be subsequently corrected. The deformed shell panels are typically straightened manually, using a flame torch to heat them up and relieve their internal stresses. The straightening process typically consists in heating specific areas of the panels and then rapidly cooling the same with water and/or any other appropriate means constraining the panels by applying force. This way of repairing the panels may however get costly and may yield inconsistent results as it is dependent on the worker's skills level. The present subject-matter may also have applications other than panels, such as any metallic structure or component having undergone a thermal cycle (heating) or having been subjected to external constraints that produce internal constraints that are sufficient to cause the metallic structure to deviate from its nominal shape (and/or dimensions). A welded part will become deformed and can thus be considered to be straightened or corrected using the present method and system. The metallic structure may be made of panels, sheets, extrusions, beams, rolled or formed tubes, etc. There are numerous applications for these metallic structures in many technological fields, such as vehicles, bridge decks, etc. It is noted that, depending on the specific application, an appropriate heat source would be used. It is further noted that the present method would not apply to parts that require to be hammered in order for them to adopt their nominal shape and/or dimensions.

The present subject-matter is thus directed to the straightening of panels, such as vehicle body panels, including panels made of sheet metal (also known as skins) or of the double-sided hollow extrusion type. It also proposes the use of robots (which is understood here to potentially include a robotic arm) and optical measuring of the panel's surfaces to conduct the straightening thereof, as described in more details hereinafter. The same straightening method may potentially be applied to other applications where deformations occur following a manufacturing step, such as after a welding operation. It should be noted that in the present description, the term straightening or straight should be understood as meaning substantially back to its original or originally intended shape, whether a 2D or a 3D shape. Panels may be flat or curved and may have a rectangular or any other geometric or irregular shape required to make up the shell covering the exterior of the vehicle.

Applicant considers that the use of an automated straightening system can reduce the costs and time spent on straightening the external panels of its vehicles by having the automated straightening system automatically generating and applying the straightening procedure based on a digitization of the panels' surfaces. The straightening is then carried out by virtue of laser-created residual stresses on the surface of the panels, these residual stresses opposing the stresses already present as a result of the welding operation. The automation of the process is based on the manipulation of data generated by the 3D digitization of the panels or parts to be straightened.

The present method can, for example, be described in four major steps, as schematically illustrated in <FIG>. First, a sub-assembly or panel <NUM> is scanned at a first scanning step <NUM>. Second, the scanning results are compared with reference data at comparing step <NUM>. Third, an analyzing step <NUM> is conducted to determine and select straightening parameters. Finally, a straightening step <NUM> is performed to straighten the panel <NUM>. These steps will now be described in more details.

The scanning step <NUM> is performed using a measurement device (optical, mechanical), such as a 3D scanner. In the present example, the measurement device is an optical sensor <NUM> that uses, for instance, laser triangulation to make physical measures/characterizations of the panel <NUM>, with photogrammetry being a possible alternative to laser triangulation. Note that a position sensor, such as a Faro arm could also be used, but it usually requires more time to scan the surface. Thus, in the scanning step <NUM>, the optical sensor <NUM> is used to scan the panel <NUM> and provide a cloud of data points corresponding to the surface of the panel <NUM>, each point of the cloud of points being defined by its own 3D coordinates (X, Y, Z).

Although the optical sensor <NUM> may be manually operated, the manipulation of the optical sensor <NUM> over the surface is preferably automated using a robot <NUM>, typically having a robotic arm, to which is connected the optical sensor <NUM>. The robot <NUM> is therefore operative to manipulate the optical sensor <NUM> so as to scan the entirety of the one or many panels <NUM> making up the vehicle shell. The robot <NUM> may be fixed to a static base and have a sufficient reach to scan the whole vehicle or it may be fixed on a mobile base which may move along the vehicle. Alternatively, the vehicle may move along a longitudinal axis, for example, and the robot <NUM> may be fixed on a static base. In any case, the objective is for the optical sensor <NUM> to be able to completely scan all of the panels of the vehicle shell.

At the comparing step <NUM>, the gathered data is then compared with the desired result (e.g.: tridimensional CAD) by a computer software <NUM>. More particularly, in the comparing step <NUM>, the cloud of points obtained in the scanning step <NUM> and representing the scanned surface of the panel <NUM> is compared with a reference surface (which may be a 2D or a 3D CAD model). The comparison is made by comparing, for example, the Z coordinate of the scanned and reference surfaces, assuming that the X and Y coordinates are located in a flat plane of the reference surface. As the Z coordinate represents a height of a point above the reference surface, the deformation is determined by the difference between the scanned Z coordinate and the reference Z coordinate. In other words, for an identical X and Y coordinate, the Z coordinate is compared between the scanned panel surface and the reference surface, such that a deformation of the panel can be determined along the Z axis. This comparison step is performed using a software and computer so that it can be rapidly and accurately performed.

Once the comparing step <NUM> is completed, a controller, which may use a computer and software <NUM>, performs an analysis at the analyzing step <NUM> to select or define the proper parameters to be used for the upcoming straightening procedure of the straightening step <NUM> to be applied to each area of the panel <NUM> requiring straightening, as determined by the comparing step <NUM>. The defined parameters may be selected from at least a trajectory, which the straightening tool is intended to follow over the deformation, a lead speed of the straightening tool <NUM>, a position of the straightening tool <NUM>, a laser power, etc. These can be monitored and, when required, adjusted during the straightening process.

To select the proper straightening parameters in the analyzing step <NUM>, the software may use preset values or procedures, whether predefined or not, developed for a specific area. For instance, the intended (i.e. non-deformed) shape of the panel is preprogrammed and, in the comparing step <NUM>, the measurements gathered in the scanning step <NUM> by the optical sensor <NUM> are compared with the preprogrammed or preset data of a non-deformed panel.

The computer and software <NUM> may also act in an intelligent manner, by using an algorithm to calculate the proper path and parameters to correct the measured deformations. Such an algorithm may be defined empirically (by way of prior experiments) or by any other adequate means, such as artificial intelligence or other self-teaching techniques or machine learning techniques.

<FIG> illustrates an example of a flow chart that is used for the analyzing step <NUM> of <FIG>. More particularly, once the gathered data of the panel <NUM> scanned during scanning <NUM> has been compared with the desired result, the algorithm verifies at <NUM> if there is a standard corrective procedure for the identified deformation. In the affirmative, the corrective parameters for this deformation are transferred at <NUM> to an automated straightening controller used during the straightening step <NUM>. In the negative, the database is searched at <NUM> for known procedures associated with a similar deformation case.

The results of this search are at <NUM>, and if a similar deformation case has been found, then the parameters of this similar deformation case are transferred at <NUM> to the automated straightening controller. If at <NUM>, no similar deformation case has been identified, an algorithm is used at <NUM> to develop a new straightening procedure adapted and appropriate for the specific deformation case.

A flow chart of an example of an algorithm A used at <NUM> by the automated straightening controller is shown in <FIG>. In <FIG>, the algorithm A looks for the maxima, i.e. the highest deformation points for each portion along the length of the scan. In the present example, the case is simplified as it represents a scanned area of the panel <NUM> having a single crest.

More particularly, the algorithm A first loads at <NUM> the 3D scan of the panel to straighten, and then removes at <NUM> data points that are considered invalid. At <NUM>, the algorithm A slices the scanned surface in small strips of a determined width (the width corresponding to the X axis), thereby creating areas, strips or portions <NUM> of the surface to be analyzed. <FIG> depicts the scanned surface and each portion <NUM> to be analyzed. The width of those portions may vary depending on the required accuracy. At <NUM>, the algorithm A screens the data points and retains only the data points for the current portion. Such data points are shown at <NUM> in <FIG> illustrates a schematic graph of an exemplary portion analysis, associated with the flow chart of <FIG>.

For each portion <NUM>, the algorithm A then determines at <NUM> a cross-section <NUM> of the portion <NUM> in the YZ plane using the cloud of data points <NUM>, as shown in <FIG>. The algorithm A then determines at <NUM> a median line <NUM> describing the shape of this cross-section <NUM>. At <NUM>, the algorithm A determines a maximum <NUM> (the highest point in the Z direction) of the median line <NUM>, and then at <NUM>, the algorithm A computes a polynomial expression that best matches the shape of the median line <NUM>. When plotted, this polynomial expression corresponds to a trend line <NUM> in <FIG>.

At <NUM>, the algorithm A computes the derivative of the polynomial expression and, using the numerical values of this derivative on both sides of the maximum <NUM>, the algorithm A computes a ridge angle θ, herein referred to at <NUM>, for the current analyzed portion. At <NUM>, the algorithm A determines if the portion <NUM> just analyzed is the last portion of the scan to be analyzed; if it is not the last portion, then steps <NUM>, <NUM>, <NUM>, <NUM> and <NUM> are repeated. As shown in <FIG>, once all the cross-sections <NUM> of all portions <NUM> to be analyzed have been analyzed, an image of the scanned surface may be created, the maxima <NUM> representing a plurality of summits making up a ridge line <NUM>, and a mean ridge angle for all portions is computed at <NUM>.

The algorithm A then determines at <NUM> if the mean ridge angle is above a predetermined threshold angle. If the mean ridge angle is above the threshold angle, the algorithm A selects the severe bend program at <NUM>, whereas if the mean ridge angle is not higher than the threshold angle, the algorithm A selects the moderate bend program at <NUM>. Optionally, more than one threshold could be predetermined such that this selection would be made from more than two different programs.

The algorithm A then generates at <NUM> the program for the robot <NUM>, wherein the maximum <NUM> of the cross-section <NUM> of each portion <NUM> becomes a point on the trajectory of the straightening tool. It is however possible that the algorithm A determines that the trajectory of the tool passes next to at least some of the maxima <NUM>, and thus not directly thereon. <FIG> exemplifies these maxima <NUM>, the highest deformation points of each determined cross-sections <NUM> of the scanned portions <NUM> of the panel <NUM>. Again, the series of maxima <NUM> define the ridge line <NUM>, which corresponds also to the trajectory of the straightening tool. The various shades of grey in <FIG> indicate the level of deformation, corresponding to displacements of the surface of the panel <NUM> along the Z axis. The darker zones along left and right sides of the panel <NUM> show a smaller deformation than that of the lighter grey zones appearing in the middle thereof.

The exemplary algorithm A selects a straightening strategy, that is a specific combination of parameters (speed, power, etc.) as a function of the level of deformation detected on the panel <NUM>. In the present example, only two levels of deformation are used: < <NUM> degrees (moderate bend at <NUM>), and > <NUM> degrees (severe bend at <NUM>). To recognize the deformation levels, a data bank of <NUM> sample measurements (<NUM> per deformation level) was made available to the algorithm A for comparison.

The straightening strategies may be obtained by experimental investigation. These straightening strategies take into consideration temperature limits and heating duration limits associated with the panel <NUM>. These limits are specific to the material and are available from the literature, e.g. encyclopaedias. In the present example, the only parameter being adjusted is the laser power level. Also, in the present example, there is no dwell time in that the laser follows a continuous trajectory, i.e. without stopping, whereas when a flame torch is used to straighten a panel, it is often necessary to leave the flame at a same location for a certain period of time in order to allow it to reach the appropriate temperature for a precise area of the panel.

Finally, the robot <NUM> executes at the fourth straightening step <NUM> the operations specified by the automated straightening controller, which uses the software <NUM>, taking into consideration the defined parameters at the analyzing step <NUM>. The operations are contained in the straightening strategy. The robot <NUM> uses a straightening tool <NUM> with the defined parameter(s) specified at the analyzing step <NUM> to conduct the straightening process. The straightening tool <NUM> may be, but is not restricted to, a laser, an induction machine, or any other adequate device that can heat or induce heat in the panel <NUM> to be straightened. As shown at <NUM> in <FIG>, various controls and adjustments can be provided in the straightening step <NUM>. For instance, a temperature monitoring device may be used during the straightening process to ensure proper heating temperatures. This temperature monitoring device could be, for example, a pyrometer or an infrared camera.

In the present example, applying the straightening strategy is sufficient to straighten to an acceptable level the surface of the panel <NUM> to be straightened, such that no physical intervention by a constraint mechanism needs to be used.

Economically, both robots <NUM> and <NUM> may actually be replaced by a single robot equipped with a tool rack, allowing it to change its own tools. For example, while the straightening tool <NUM> is used, the optical sensor <NUM> may be placed in the tool rack and vice versa.

Optionally, the optical measurements could also be conducted almost simultaneously during the straightening process of the straightening step <NUM>. In this case, the single robot <NUM> holds both the optical sensor <NUM> and the straightening tool <NUM>. The optical sensor <NUM> scans the surface of the panel <NUM> ahead of the straightening tool <NUM> and sends the scanned data to the controller for analysis at step <NUM>, which defines the required parameters at step <NUM> and which controls the straightening tool <NUM> based on those defined parameters. Such a continuous online, or real-time measurement and straightening process may then include a system that is directly adaptive during the straightening process. Such a system may, for example, adapt the straightening parameters depending on the reaction of the treated area in a "live" or real-time manner.

The four steps <NUM>, <NUM>, <NUM> and <NUM> may also be conducted iteratively until the desired results are obtained. After straightening, a final scan may be performed in order to provide a final distortion report to workers.

The present method potentially reduces the straightening time, and also reduces the variability related to worker skills and perceptions. Furthermore, the proposed method improves the results and precision of the straightening process. Interestingly, the present straightening process may also contribute to decreasing the weight of a finished vehicle as putty used to even the surface of the external panels of the shell is reduced or even eliminated.

Claim 1:
An automated method for at least partly correcting deformations in a metallic component (<NUM>) and the like, the method comprising:
a) scanning (<NUM>) a deformed surface of the metallic component to gather data thereon;
b) comparing (<NUM>) the gathered data of step a) with a desired result;
characterized in that the method further comprises:
c) performing an analysis (<NUM>) of the compared data of step b) for identifying highest deformation points of adjacent portions of the deformed surface of the metallic component;
d) determining a trajectory substantially passing by at least two of the highest deformation points; and
e) executing (<NUM>) on the deformed surface correcting operations, comprising heating the metallic component (<NUM>) along the trajectory.