MANUAL WELDING METHOD AND WELDING ROBOT [...] IMPLEMENTING SUCH A METHOD

The present invention relates to the field of assembling of parts by providing heat, as the welding and brazing, and more particularly to assist the creation of such joints.

Welding and brazing are reliable techniques for joining by heat input of metal elements or not. The portions of the members to be joined are placed opposite one another and define a joint plane which is subjected to the heat with or without supplementation of joining material. The brazing denotes the techniques wherein junction are removed by diffusion, [...] without melting components to be joined. The welding denotes the methods in which the parts to be joined are melted. Regardless of the methods used (MIG welding, TIG welding, submerged arc, flux-cored wire, covered electrode, and so on.), it is necessary to be able to control the trajectory of the point of heat supply (electrode, flame of the torch, laser beam, and so on.), its rate of movement relative to the assembly as well as the distance at which it is located components to be joined. The voltage, the magnitude and polarity of the arc when the heat supply involves an electric arc, the gas flow rate, the supply of an optional filler material are also assembly parameters that require monitoring, particularly during a change position being welded (case of the burnishing tool for example). These assembly parameters influence the quality of the assembly (or solder) obtained. Of factors related to the elements to be assembled such that the level of preparation of the joining seam in particular whether or not the geometrical defects in the seals or local changes the nature of the materials to be joined includes produce of the assembly. It is then necessary to adapt in real time the assembly parameters during the production thereof. This is done by monitoring the melt (or soldering) which is a reliable indicator of the conformity of assembly parameters. The multitude of parameters monitoring and analysis of the melt require a skill that it is difficult to automate. Thus, the welding or brazing operations are generally performed manually by skilled operators. These are then exposed to fumes of welding, to the UV radiation of the heat source and must sometimes enter into little ergonomic, especially during assembly of cylindrical elements that require a posture called "ceiling" in which the heat supply is below the assembly, generally involving the operator to position the heat supply above it, in a position particularly uncomfortable. Operator intervention impacts the repeatability of assembly operations and represents a source of uncertainties, thus variability in the quality of the completed assembly.

It is known robots weld comprising an articulated arm on which is mounted a welding torch, generally MIG or MAG, and are programmed to carry out a torch travel according to predefined parameters, on a known path. Also known orbital welding robots which the welding torch is mounted on an annular bearing concentric to the tubes to be joined. A robot orbital welding requires almost a robot specific to each tube diameter and is substantially limited to the butt joints, excluding the automation of certain types of assembly, as the tappings for example. Such robots require a rigorous preparation components to be joined and more tests to determine the welding parameters. Each type of assembly must be subjected to a specific programming and new tests up to the enabling of the welding parameters. This lack of versatility in that these robots are not adapted to the production unit or to small and medium series, for which reason the series are still processed by manual welding. Thus such products suffer from a high variability in the quality of assemblies performed which is specifically for origin in working conditions difficult conditions operators.

One aim of the invention is to improve the quality of manual assemblies by supplying heat.

To this end, there is provided a method of assisting in achieving the connection between two elements by supplying heat, such as a weld or braze, the method being implemented by means of a robot remote-operated, the robot comprising:

- an articulated arm at the end of which is mounted a heat supply, such as a nozzle or an electrode, the heat supply being adapted to provide heat at a heat supply;

- sensors detecting the position of the articulated arm;

- actuators guide of the articulated arm;

a video capture device - the point of heat supply;

- a haptic interface for controlling the trajectory of the point of heat supply and assembly parameters; a processing and control unit connected to the position sensors, guide to the actuators, the video capture device, the haptic interface for controlling the trajectory and assembly parameters. According to the invention, the method comprises the following steps:

a) acquiring a type of assembly to be performed;

b) calculating a reference trajectory of the point of heat supply;

c) defining a guide casing member heat supply around the reference trajectory;

d) control actuators guide so as to oppose movement of the delivery member of heat outside the guide shell, providing a force feedback to the haptic interface.

Thus the ability of the operator to intervene on the welding parameters when necessary is maintained and reinforced by the fact that some parameters are, by default, automatically controlled. The operator is then able to fully focus on the critical parameters and their evolution into the behavior of the assembly at the point of heat input. The telop greatly improves the conditions of operator intervention, particularly with regard to its exposure to the fumes, UV radiation or the usability. Finally, the haptic interface maintains the indispensable feed of the turn of the hand of the operator. All of these improvements conditions of execution of the assembly positively impacts the quality of the assembly.

Advantageously, the haptic interface comprises a master arm force feedback. Such a haptic interface allows to adapt the method to a large number of welding tools while remaining as closely as possible to the gesture natural normally performed during manual assembly operations.

According to a particularly advantageous embodiment, step c) of defining a guide casing comprises the following steps:

i.) generating by the processing unit and control of an articulated arm virtual and removable heat input virtual;

c. ") generating a virtual guide casing by the processing and control unit;

and step d) control actuators guide comprises the following steps:

of) a bilateral coupling embodiment in position between the haptic interface and the articulated arm virtual;

d. ") performing a unilateral coupling position of the pivot arm of the articulated arm and virtual;

d." ') control the haptic interface so as to counteract a displacement of the virtual heat supply outside the envelope of virtual guide, whilst coupling the position of the haptic interface device and of the articulated arm.

The use of three-dimensional modeling allows to lighten the resources needed for computation of interference and determining forces to be returned by the processing unit and to control the haptic interface. Applying stress guide at virtual single articulated arm relieves the control volume to be sent to the actuators guide of the pivot arm are not then in efforts to strong but only guide forces.

Advantageously still, the guide actuators are controlled so as to authorize a scanning movement of the point of heat input of each side of the reference trajectory, the scanning movement being controlled by the operator from the haptic interface. The operator can then be used to produce for elements of great thickness and/or chamfered that require scanning between the two elements, particularly the phases fill and finish when the joint is a weld joint.

According to a particular embodiment, the actuators are controlled guide so as to force the point of heat input to track the reference trajectory. This allows a precise application of the point of introduction of heat, particularly for butt welds, and can thus limit the heat affected zone heat input, terminating to a assembly of higher quality.

In another particular embodiment, step b) of calculating the reference trajectory of the point of introduction of heat uses at least one of the following parameters: a joint plane geometry, geometry of the elements, the assembly method. The operator is then discharged operations that are not exclusively in management of the assembly at the point of introduction of heat such as the interference management of the arm with the parts to be joined. Identical purposes, the definition of the guide shell will take into account at least one of the following requirements: maintaining orthogonality of the heat supply to the surface of at least one of the elements, holding the end of the member for heat supply a joint plane, absence of collision between the heat supply, the arm and the elements to s e emb1er.

Advantageously, the method comprises the further step of storing the type of assembly, the reference trajectory of the point of heat input as well as the trajectory of the point of heat supply actually performed. Thus, the processing unit can build a library of trajectories and adapt the future path calculations point reference heat supply based on trajectories actually performed using, for example, learning algorithms.

The invention also relates to a robot remote-operated of comprising:

- an articulated arm at the end of which is mounted a heat supply, such as a nozzle or an electrode, the heat supply being adapted to provide heat at a heat supply;

- sensors detecting the position of the articulated arm;

- actuators guide of the articulated arm;

a video capture device - the point of heat supply;

- a haptic interface for controlling the trajectory of the point of heat input and welding parameters;

- a processing and control unit connected to the position sensors, guide to the actuators, the video capture device, the haptic interface to control the trajectory and welding parameters.

The processing unit is arranged for carrying out the method according to the invention.

Other features and advantages of the invention will be apparent in the description that follows of particular embodiments of the present invention non-limiting.

It will be referred to Figures appended including:

figure 1 - is a schematic representation of a robot remote-operated according to 1' a;

figure 2 - is a perspective view of a processed by the robot assembly of Figure 1;

figure 3 is a - [...] steps of the method according to the invention;

figure 4 - is a schematic representation of a three-dimensional model of the robot of Figure 1.

With reference to Figure 1, the method is implemented by means of a robot remote-operated, generally designated 1, comprising an arm 10 polar modifiers having six joints 11.1 to 11.6 rotoid type.

A MIG welding torch 20 is mounted on the end 12 of the arm 10 and comprises a guide tube for a wire 22 21 metal from a reel controlled 23. The guide 21 is connected to the terminal 24.1 positive generator 25 electric welding. An assembly 40 of two metal tubes 41 and 42 is in turn connected to a second terminal of the generator 25 24.2 mass. Thus the wire 22 serves as an electrode and enables the establishment of an electric arc heat-emitting a point heat supply 43 on the assembly 40. The MIG welding torch 20 also includes a diffuser 26 of inerting gas argon herein - 27 - 28 from a reservoir in which is mounted a pressure reducing assembly/flowmeter 29. A tubular nozzle 30 extends around the guide 21 and 26 of the diffuser. The arm 10 also includes sensors 13.1 to 13.6 its position as well as actuators guide 14.1 to 14.6, respectively implanted at each joint 11.1 to 11, 6. The arm 10 further includes a camera 31 liquid-cooled and positioned to capture a picture of the point of heat input 43. The camera 31 is provided with an optical filter 32. The robot 1 also includes a haptic interface 50 for controlling the trajectory of the point of heat supply 43 and welding parameters. The haptic interface 50 comprises in particular a screen 51 reproducing the images captured by the camera 31, a joystick type 6d 52 "[...]" of [...] (registered trademark) 3, a master arm 52, 1 force feedback with a reproducing 52, 2 of the welding torch 20, a pedal control 53 priming and intensity of the welding current, a manual control 54 speed of feeding of the wire 22, a control 55 of flowmeter 29 of inerting gas 27, an interface 56 selecting and instructing in the form of a mouse and a keyboard 56, 1 56, 2. The master arm 52, 1 force feedback can be an arm-like "virtuoso 6d" (registered trademark) of [...].

Finally, a processing and control 57 comprises computing means 58, 59 and a memory is connected to the position sensors 13.1 to 13.6, guide to the actuators to 14.6 14.1, to the camera 31, 53 to commands to the pedal 54 and 55 and to the haptic interface 50.

With reference to Figures 2 and 3 and 60 according to a first step of the process, the operator selects the type of assembly to be performed among predefined types of mounting (linear joining, stitching, and so on.) using the interface 56. Here, the operator selects a bundle of tubes end to end. This allows the processing unit 57 to acquire the type of assembly to be performed. In a second step 61, the operator moves the arm 10 until the guide 21 is in contact with the exterior of the tube 41. This contact is identified by the unit 57 which measures a zero resistance between the terminals of the generator 25 24.1 and 24.2. Other two shots of point on the outside of the tube 41 57 allow the unit to determine the diameter of the tube 41. The thickness of the tube will also be determined by either the keyboard 56, 2 or by measuring point on the interior of the tube 41 by the guide 21 into contact with the inside of the tube 41, the axis along which extends the tubes 41 and 42 being known. Finally, the nature of the material of the tubes 41 and 42 will also be determined by measuring the conductivity of the metal. This second step 61 is optional since acquiring the type of assembly to be performed and its specific parameters may be performed by input by the operator via the interface 56.

In a third step 62, the processing unit 57 calculates a reference trajectory point 80 heat supply 43 by using at least one of the following parameters: a joint plane geometry, geometry of the elements, the assembly method. The dividing plane is defined as an area which the guiding curve is the assembly line elements 41 and 42 and the surface of which groups the medial axes of the elements 41 and 42. The processing unit 57 will then define a linear path which thereby avoids interference between the torch 20, the robot 10, 41 and 42 members and which is located in the joint plane. The distance between the end of the guide 21 out work is determined depending on the type of welding to be performed (welding short arc, welding by axial spray or globular transfer welding). It should be noted that this type of welding can be set by default or selected via the interface 56. The type of welding also determines the voltage ranges and intensity to be applied.

According to a particular embodiment, the unit 57 generates a virtual articulated arm 110 in the form of a three-dimensional computer model which corresponds in every point in articulated arm 10 (geometry, degrees of freedom, and so on) and its accessories virtual camera 131, virtual torch 120 as well as flexible virtual gas supply wire 22. this three-dimensional computer model may also include a three-dimensional representation of the assembly 40 in the form of a virtual assembly 140. Finally, the articulated arm 110 comprises a point of heat input virtual 143 corresponding to a calculated position of the point of heat input 43 from welding parameters default. The position of the point of heat input virtual 143 is updated according to the movements of the articulated arm virtual 110 and progress of welding parameters. Such a three-dimensional computer model is shown in fig. 4.

The unit 57 performs a bilateral coupling position between on one hand the haptic interface essentially the master arm 52, 1 and the joystick 6d 52-and on the other hand the virtual articulated arm 110. This means that the position of one of the coupled elements is transferred to the other bilaterally (first liquid to the second and from the second to the first). Thus, a change in the position of the master arm 52, 1 is immediately reflected on the virtual position of the pivot arm 110. Similarly, a virtual constraint applied to the horn virtual 110 - e.g. an interference with the assembly 140 - se results defined by the control unit 57 to the master arm 52, 1 so as to apply a resistive force on the master arm 52, 1.

The unit 57 also controls the actuators position 14.1 14.6 to guide so that the position of the articulated arm virtual 110 is produced on the articulated arm 10.

In a third step 63, the unit 57 defines a guide shell 81 of the torch 20 around the reference trajectory 80 set at step 62. defining the guide casing 81 takes into account at least one of the following requirements: maintaining orthogonality of the torch 20 against the surface of the member 41 or 42, holding the end of the guide 21 in the joint plane, absence of collision between the torch 20, the arm 10 and the members 41 and 42. The unit 57 model the guide casing 81 of the torch 20 as a virtual guide casing 181 of the torch virtual 120 extending around a virtual reference trajectory 180 modeled in the environment of the virtual arm 110. selon a fourth step 64, the operator sets initial parameters of welding (welding voltage, speed of feeding wire 22, rate of inerting gas 27). This step 64 is optional because the operator may choose to store parameters of welding defect or validate welding parameters defined by 1' unit 57.

Once these operations performed, the joining of parts can begin.

According to a step 65, the processing unit 57 controls the actuators to guide 14.1 14.6 to bring the torch 20 in its calculated position start welding, herein as the assembly 40. This step is optional because this implementation start position welding can be performed by the operator using the master arm 52, 1 and/or the joystick 6d 52. The operator may also perform, according to a step 66 optional control, prior inspection of the joint to be welded using the camera 32 by manipulating the arm 10 using the joystick 6d 52, of the master arm 52. the Lou by instructing the unit 57 controls the actuators of 14.1 14.6 to guide such that the arm 10 describes the corresponding movement with movement of heat supply 43 along the reference path 80. according to a step 67, the operator initiates the start of welding. This welding step is triggered by the ignition of the electric arc welding through the pedal 53 with which the operator can also adjust the intensity of the welding current. Substantially simultaneously to the initiation, the controls 54 and 55 respectively trigger wire supplies are 22 and 27 according to the inerting gas welding parameters previously defined. Finally, once the electric arc between the tube 21 and the assembly 40, the unit 57 controls the haptic interface 50-and more particularly the force feedback to the master arm 52.1 - de so as to maintain the speed of movement of the heat supply relatively to the virtual 143 140 virtual assembly at a speed of between fifteen and forty centimeters per minute along the path virtual reference 180. This control is felt by the operator via the haptic interface unit 50 and 57 also controls the actuators to 14.6 14.1 of the articulated arm 10 so that the articulated arm 10 reproduces the virtual position of the pivot arm 110, and thus reproduces the stress speed maintenance within the defined range.

During the assembly operation, the operator monitors on the screen 51 the picture captured by the camera 31 heat supply point 43 and thus analyze the melt. He may act accordingly on the welding parameters (intensity, wire speed, gas flow rate, length of the arc, polarity of the voltage, and so on) and on movement of the point 43 via the application of heat and/or a joystick 6d 52 the master arm 52, 1. The operator can also adjust the position of the MIG welding torch 20 by acting directly on the master arm 52, 1 so as to move the point of heat input 43 according to the state of the melt. All changes in position of the arm 52, 1 is transmitted to the master unit 57. According to a step 68, the control unit 57 force feedback on the master arm 52, 1 so as to oppose a displacement of the master arm 52, 1 is causing a virtual 120 torch travel outside the envelope of virtual guide 181. Such a force feedback can be likened to an applied force on the virtual guide virtual articulated arm 110. The position of the master arm 52, 1, subject to the operator and jointly at force feedback controlled by the unit 57, is reproduced on the articulated arm 10.

The unit 57 may control the application of elastic forces which opposes the movement of the welding torch virtual 120 and whose magnitude ranges in increasing manner as approaching the limits defined by the virtual guide casing 181, or apply a zero effort within the virtual guide casing 181 and then a reactive force of elastic stop when the welding torch virtual 120 reaches the limits of the guide shell virtual 181.

The control of the force feedback by the unit 57 on the master arm 52, 1 may also allow or restrict other movements such as:

a) allowing a scanning movement of the point of heat input virtual 143 on either side of the path of virtual reference 180, this scanning movement being controlled by the operator from the haptic interface 50;

b.) constrain the point heat supply 43 to track the reference trajectory 80.

The scanning movement of the point of supply of heat thereto virtual 143 can also to be a command issued by the unit 57 on the master arm 52, 1 to generate an elastic force when the welding torch approach limits defined by the virtual guide casing 181. The unit 57 may alternatively control the application by the force feedback of the master arm 52, 1 of zero effort within the virtual guide casing 181 and then a reactive force of elastic stop when the welding torch virtual 120 reaches the limits of the guide shell virtual 181.

Note that the guide casing 81 defines the possible positions of the heat supply - here the wire end 22 of the MIG welding torch from 20 - when the reference trajectory 80 defines a theoretical trajectory of the point of heat input 43. Inside the guide casing 81, the heat supplying member movable to a plurality of positions in which the point of heat input 43 remains on the reference trajectory 80. these various possible positions can avoid collisions and maintains a good visibility of the melt or lengthen the electric welding arc without changing the position of the point of heat input 43. The point of heat supply 43 may also deviate from the reference trajectory 80 as the heat supply remains within the guide casing. In any case, the definition of the guide casing 81 takes into account the possible movement of the point of heat input 43. The same considerations apply to the virtual guide casing 181, the torch virtual 120, the virtual reference trajectory 180 and the point of heat input virtual 143.

As an optional step 69, when the weld is completed, the operator performs a pass of viewing during which the unit 57 controls the actuators to 14.6 14.1 guide so that the camera 31 scans the entire weld, thereby enabling the operator to perform a visual inspection of the weld.

According to a particular embodiment, the unit 57 stores the type of assembly, the reference trajectory point 80 heat supply 43 as well as the trajectory actually performed by the heat supply point 43. A learning algorithm which is integral to the 57 adjusts for the calculation of the future trajectories of reference trajectories actually performed for similar packages.

Of course, the invention is not limited to the disclosed embodiments but encompasses any variant within the scope of the invention as defined by the claims.

In particular,

- although the assembly comprises two frame parts, here in the form of two tubes joined end to end, the invention is also applicable to other types of assembly such as taps tubes extending at an angle between 0 and 180 degrees, a gliding movement of objects in end to end or edgewise, an assembly using a tube and a flat product;

- although here the bond being made by welding, the invention is also applicable to other types of assembly by supplying heat such as brazing;

- although here the guide arm is a six-axis arm, the invention is also applicable to other types of arms such as arms provided with a different number of shafts or with a different number of degree of freedom;

- although here the robotic arm is an arm pole comprising articulations rotoid type, the invention also applies to other types of robotic arms such as for example a Cartesian arm including prismatic joints and revolute;

- although here the robot is provided with a MIG welding torch, the invention is also applicable to other welding methods such as the methods Mal, to cored wire without inerting gas, to stick electrode, wire under flow, or the methods TIG or flame brazing, laser beam or by inducing;

although here the heat supply comprises a guiding tube polarizing a wire in the form of a consumable electrode, the invention is also applicable to other types of heat supply means such as a non-consumable electrode of tungsten (TIG welding method) or other material or a delivery nozzle and heating gas (acetylene or other);

- although here the welding torch supplying device integrates the filler metal, the invention is also applicable to other types of processes without filler metal (autogenous welding without filler metal) or in which the filler metal is supplied to the molten bath by a device independent of the motor including the heat supply;

well, that here supplies are filler metal and gas are triggered automatically, the invention also applies to supplies of filler metal and gas triggered manually;

- although here the point of heat input is filmed using a camera cooled by liquid and provided with a filter, the invention is also applicable to other types of video capturing means the point of supply of heat such as a thermal camera, a camera HS, as well as other means of protection against radiation such as for example an LCD screen to automatic darkening;

although here the haptic interface comprises a joystick type 6d "[...]" and a master arm force feedback with a reproduction of a welding torch, the invention is also applicable to other types of haptic interface such as an interface having two manipulators to force feedback, or one or more [...] to force feedback;

- although here the master arm force feedback either type "virtuoso 6d" of [...], the invention also applies to other models of master arm force feedback as well as other manufacturers of such arms;

although here the acquisition will occur in the assembly of the guide tube with wire used as a contact sensor, the invention is also applicable to other acquisition means such as two-dimensional acquisition means such as a camera, a sensor element or means for acquiring three-dimensional such as 3d scanner, a pair of cameras 2d or of the ultrasound probes;

- although here the moving speed of the heat supply is between fifteen and forty centimeters per minute, the invention is also applicable to other predetermined ranges of travel speed of the heat supply as for example at speeds less than fifteen centimeters per minute or greater than forty centimeters per minute;

- although here the processing unit and generates a control virtual articulated arm and a virtual model accessories that are attached (camera, welding torch, like), the invention is also applicable to a modeling only comprising an arm member and a virtual virtual heat input;

- although here the method comprises generating a virtual articulated arm and a heat supply for virtual then determine a virtual guide casing, the invention also applies to a method lacking steps of generating virtual elements and wherein the interference situation, and the coordinates of the various elements are calculated without passing through a three-dimensional modeling. The processing unit and then directly controls the actuators of the guide oppose directly to a travel of the supply of heat from the casing is calculated driving. The direct connection of the haptic interface device and articulated arm is a return guide forces applied to the articulated arm to the haptic interface to allow the operator the feel;

- although here the virtual arm or a three-dimensional computer model, the invention is also applicable to other types of computer models such as a wire frame model, two-dimensional.