JPH04220190A - How to control a laser robot - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] This invention relates to a laser robot, a control method thereof, and a light beam deflection device applicable to laser robots, etc., and in particular, it relates to a device for periodically changing the irradiation direction of a laser beam emitted from a torch. Regarding the technology to make it happen.

0002

BACKGROUND OF THE INVENTION Laser robots are used for various purposes, but recently their use as welding robots has been attracting attention. However, in butt welding, etc., the gap between the workpieces is often not uniform, and the spot diameter of the laser beam is quite small, so it is necessary to perform so-called weaving welding, in which welding is performed while changing the irradiation direction of the laser beam. There is a problem that it is not possible to obtain accurate welding results. Therefore, when using a laser robot as a welding robot, it is necessary to improve its weaving performance.

Conventionally, it is known that there are roughly two types of methods for providing a weaving function to a laser robot.

The first method is a method conventionally used in arc welding robots, etc., in which the laser torch LT itself periodically swings in a direction perpendicular to the groove direction, as shown in FIG. 39(a). In this method, the laser torch LT is moved along the groove direction (arrow A1).

Second, as shown in FIG. 39(b), the laser torch LT is moved in the direction of the arrow A2 along the groove direction, and the deflection angle of the laser beam emitted from the laser torch LT is adjusted according to the arrow A2. This is a method of changing periodically as shown by A3. Known methods for achieving this second method include: ■ Periodically vibrating or rocking the condensing lens for the laser beam, and ■ Deflecting the laser beam using a combination of a pair of galvano mirrors. There is.

[0006]

However, the first method described above has a problem in that the welding speed is slow because the movement of the arm for swinging the torch cannot be made very fast.

On the other hand, in method (2) of the second method, since the condenser lens is provided near the tip of the arm,
It is necessary to attach a lens drive mechanism to the tip of the arm. This increases the size and inertia of the arm tip, leading to problems such as increased interference between the arm tip and obstacles and decreased controllability.

[0008] Also, in method (2) of the second method, a problem arises in that it is not easy to control the drive of the galvanometer mirror. That is, since the laser used for welding is a high-power laser (for example, a CW oscillation carbon dioxide laser), the material and thickness of the galvanomirror itself must be able to withstand the high power, and inevitably Its inertia also increases. Furthermore, since the galvanometer mirror must be vibrated at a high frequency, the torque load on the vibration mechanism changes drastically. As a result, it becomes difficult to synchronize the vibrations of each galvano mirror.

The above-mentioned problem is not limited to welding robots, but is common to laser robots in which it is necessary to periodically deflect a laser beam.

The present invention has been made to overcome the above-mentioned problems, and it is possible to prevent interference between the tip of the arm and an obstacle when periodically deflecting a laser beam, and to prevent the periodic deflection of the laser beam. The first object of the present invention is to provide a laser robot that is easy to control, has excellent control accuracy, and can increase the deflection speed and therefore the welding speed sufficiently.

A second object of the present invention is to provide a laser robot control method that can control such a laser robot with high accuracy.

Furthermore, a third objective is to generalize the new configuration used in such a laser robot as a light beam deflection device.

[0013]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides a new configuration in the above-mentioned second system.

That is, the laser robot according to the first configuration of the present invention has a plurality of tilt mirrors each tilted from a plane perpendicular to a predetermined rotation axis direction and rotated about the respective rotation axes. Mirror rotation mechanisms are arranged in series along the optical path of the laser beam, and the plurality of tilted mirror rotation mechanisms rotate the plurality of tilted mirrors around their respective rotation axes, and the laser beam is directed to each of the plurality of tilted mirrors. By sequentially reflecting the laser beam and emitting the reflected laser beam from the torch, the irradiation direction of the laser beam emitted from the torch is periodically deflected.

[0015] Furthermore, in the laser robot control method according to the second configuration of the present invention, in the laser robot according to the first configuration, the number of rotations of each of the plurality of tilted mirrors is made the same, and the respective rotation directions are made to be the same. Regarding the control method of the laser robot, which is the same for each other, the number of rotations of the multiple tilted mirrors is determined by the speed at which the torch moves along the processing line while performing a predetermined process, and the speed at which the torch moves within one cycle of the deflection of the laser beam. The rotational phase difference between two adjacent tilted mirrors in a plurality of tilted mirrors is determined by specifying the spin diameter of the laser beam emitted from the torch. A drive output corresponding to the rotational speed and rotational phase difference determined above is applied to the plurality of tilting mirror rotation mechanisms to control the rotation of the plurality of tilting mirrors.

[0016] Furthermore, a method for controlling a laser robot according to a third configuration of the present invention is such that, in the laser robot according to the first configuration, the number of rotations of each of the plurality of tilted mirrors is the same and the direction of rotation of each of the plurality of tilted mirrors is set to be the same. This is related to a laser robot control method in which the rotation directions of two adjacent tilted mirrors are opposite to each other, and the speed at which the torch moves along the processing line while performing a predetermined process is the number of rotations of the multiple tilted mirrors. and the distance that the torch moves along the processing line within one period of deflection of the laser beam,
The rotational phase difference between two adjacent tilted mirrors in multiple tilted mirrors is determined by the position coordinate value of the torch tip in the absolute coordinate system at the processing point on the processing line and the arm used to move the torch to the processing point. The driving amount is determined for each processing point based on the drive amount, and a drive output corresponding to the rotation speed and rotational phase difference determined as described above is given to the plurality of tilting mirror rotation mechanisms to control the rotation of the plurality of tilting mirrors. This is what I decided to do.

Furthermore, a light beam deflection device according to a fourth aspect of the present invention is intended for general devices for periodically deflecting a light beam. First and second tilted mirror rotation mechanisms rotate the first and second tilted mirrors, which are tilted from a plane perpendicular to a predetermined rotation axis direction, about their respective rotation axes. These tilting mirror rotation mechanisms rotate the first and second tilted mirrors about their respective rotation axes, and direct the light beam to each of the first and second tilted mirrors. The light beam is periodically deflected by sequentially reflecting it at the .

The rotation directions of the first and second tilted mirrors may be the same or opposite, which correspond to the fifth and sixth configurations of the present invention, respectively.

[0019]

[Operation] Each of the tilted mirrors used in the laser robot according to the present invention has the function of periodically deflecting the laser beam by rotating it. By combining a plurality of these tilted mirrors and appropriately setting their relative rotational directions, rotational phase differences, etc., it is possible to change the deflection mode, deflection period, amplitude, etc. of the laser beam.

Therefore, by specifying the moving speed of the torch, the moving distance of the torch within one period of deflection, the amplitude of the deflection mode, etc., the desired number of rotations of each tilting mirror and the rotational phase difference between adjacent tilting mirrors can be determined. can be obtained by calculation. At this time, by compensating for the influence of driving each arm of the laser robot, the rotational phase difference can be accurately determined.

Furthermore, in the present invention, the above configuration is generalized as a light beam deflection device, and a device with improved deflection accuracy and deflection speed can be obtained. Different deflection modes can be obtained depending on whether the first and second tilt mirrors have the same or opposite rotation directions.

[0022]

Embodiment (1) Mechanical configuration FIG. 2 is an external perspective view showing the mechanical configuration of a laser welding robot RB which is an embodiment of the present invention. robot R
At B, a hollow pivot column 2 is supported on the base 1 and is pivotable around a pivot axis Z. Also, rotating pillar 2
has a hollow elevating body 3 that can freely move up and down on its rotation center axis Z.
is supported. Further, the elevating body 3 supports a hollow horizontal arm 4 that is extendable and retractable on a horizontal axis Y that is perpendicular to the rotation center axis Z.

[0023] Also, a hollow first rotating body 5 that is rotatable around a horizontal axis Y is supported at the tip of the horizontal arm 4.
Furthermore, a hollow second rotating body 6 is supported on the first rotating body 5 and is rotatable around an axis V perpendicular to the rotation axis (coinciding with the horizontal axis Y). A laser torch (nozzle) is attached to the second rotating body 6 in the direction of an axis W perpendicular to the rotating axis V.
7 is attached.

The laser beam oscillated by the carbon dioxide laser oscillation device 8 is reflected downward by the reflection section 9, and the optical axis of the reflected light is aligned with the rotation center axis Z. Further, the laser beam passes through each member 3, 4, 5, and 6 while being sequentially reflected by a mirror system to be described later, and is irradiated from the tip of the laser torch 7. This laser beam is rotated by the action of a pair of tilted mirror rotation mechanisms, which will be described later.
The beam is periodically deflected with respect to the central axis W of the laser torch 7.

Therefore, as shown in FIG.
By moving in the B direction along the abutting portion 23 of the works 21 and 22 during butt welding, weaving welding can be performed on this abutting portion 23. Note that a welding rod is not used in this welding, and the workpieces 21 and 2 are
The bonding is performed by dissolving the two themselves.

(2) Optical configuration FIG. 1 is a schematic diagram showing the optical configuration of laser welding robot RB shown in FIG. 2. The laser beam LB oscillated by the laser oscillation device 8 passes through the mirror 31 in the reflection section 9.
After being reflected by, the light passes through the rotating column 2 and enters the elevating body 3.

The optical system inside the elevating body 3 includes fixed mirrors 32 to 34, a first tilted mirror 41a attached to a first tilted mirror rotation mechanism 40a, and a second tilted mirror rotation mechanism 40b. It is composed of an attached second tilting mirror 41b. Therefore, the laser beam LB that has entered the elevating body 3 is sequentially reflected by the mirrors 32, 33, and 34, and then enters the first inclined mirror 41a.

FIG. 4 shows the first tilting mirror rotation mechanism 40a.
FIG. As shown in the figure, the first tilted mirror 41a is attached to the rotor shaft 43a of the motor 42a, and its mirror surface is tilted by an angle Δθ1 from a plane PL1 perpendicular to the rotational axis direction RA1 of the rotor shaft 43a. ing. Further, the rotation axis direction RA1 is inclined by an angle θ1 from the incident axis of the laser beam LB. For this reason, the motor 42a
When the first tilted mirror 41a is rotated by , the reflection direction of the laser beam LB reflected by the first tilted mirror 41a changes periodically. That is, plane PL1
Assuming a virtual state in which the first tilted mirror 41a exists above, the traveling path RP1 of the laser beam LB when reflected in such a state will be called the "reference optical path". , the actual optical path of the reflected laser beam LB changes periodically on a conical surface having this reference optical path RP1 as the central axis. For more information on this periodic change, see
This will be explained later. The laser beam LB reflected by the first tilted mirror 41a is further reflected by a second tilted mirror 41b (see FIG. 4) provided on the extension of the reference optical path RP1.

The motor 42a has a built-in rotary encoder 44a for detecting the rotation angle of the rotor shaft 43a, and it is preferable to use a direct drive type servo motor as the motor 42a.

Furthermore, the first tilted mirror 41a is arranged so that its center (the point of attachment to the rotor shaft 43a) is on the reference optical path RP1.

FIG. 5 shows a second tilting mirror rotation mechanism 40b.
FIG. As shown in the figure, the second tilted mirror 41b is attached to the rotor shaft 43b of the motor 42b, and its mirror surface is a plane P perpendicular to the rotational axis direction RA2 of the rotor shaft 43b.
It is inclined by an angle Δθ2 from L2. Further, the rotation axis direction RA2 is inclined by an angle θ2 with respect to the reference optical path RP1 shown in FIG. Note that the angle θ1 shown in FIG.
Regarding the relationship between the angle θ2 and the angle θ2, the two values may generally be different, but in this example, for convenience, the angle θ1
= θ2. That is, the rotation axis directions RA1 and RA2 of the first and second tilted mirror rotation mechanisms 40a and 40b are parallel to each other. Further, regarding the relationship between the inclination angles Δθ1 and Δθ2, both values may be the same or different, but in this embodiment, it is assumed that Δθ1 =Δθ2.

Also, in the second tilting mirror rotation mechanism 40b, the second tilting mirror 41 is rotated by the motor 42b.
When b is rotated, the direction of reflection of the laser beam LB from the mirror surface changes periodically. The change rule is determined by the respective rotational speeds and rotational phase differences of the first and second tilted mirrors 41a and 41b, the magnitudes of the angles Δθ1 and Δθ2, and the details will be described later. Further, assuming a hypothetical state in which the mirror surface of the second inclined mirror 41b exists on the plane PL2 and the laser beam LB is incident along the reference optical path RP1, the reflected laser beam LB at that time is The optical path becomes the reference optical path RP2.

Furthermore, a rotary encoder 44b for detecting the rotation angle of the rotor shaft 43b is built in the motor 42b, and it is preferable to use a direct drive type servo motor as the motor 42b.

[0034] Also, regarding the second tilted mirror 41b,
It is arranged so that its center (the attachment point to the rotor shaft 43b) is on the reference optical path RP2.

The pair of tilt mirror rotation mechanisms 40a and 40b shown in FIGS. 4 and 5 may be combined into one module as a light beam deflection device.

Returning to FIG. 1 again, the laser beam LB that is sequentially reflected by the first and second tilted mirrors 41a and 41b and output from the optical system 30 in the elevating body 3 travels inside the horizontal arm 4. Fixed mirror 35 inside the first rotating body 5
reflected. Further, the reflected laser beam LB is converted into a focused beam by a parabolic mirror 36 provided in the second rotating body 6, and is irradiated from the torch 7 toward the workpiece. Actually, the first and second tilted mirrors 41a,
By rotating 41b, the first tilting mirror 4
The traveling direction of the laser beam LB after being reflected by 1a changes periodically, but in FIG.
The direction of travel is representatively shown.

(3) Electrical Configuration FIG. 6 is a control block diagram of the first and second tilting mirror rotation mechanisms 40a and 40b shown in FIGS. 4 and 5. The input/output device 53 provides information regarding the operation of each arm of the robot RB shown in FIGS. 1 and 2 as well as information regarding welding conditions. This information is sent to the robot controller 5.
Incorporated into 2. The robot controller 52 generates output command values for the motors for driving each arm of the robot RB, and also controls laser ON/OF for the laser oscillation device 8.
Generate F command value. Furthermore, the robot controller 52
is the motor 42a for the motor controller 51.
, 42b, respectively, the rotational speed command values N1 and N2
and initial phase command values φ1 and φ2 are given together with a rotational direction command value (not shown).

The motor controller 51 outputs motor drive powers D1 and D2 to the motors 42a and 42b based on these command values. Moreover, the rotation angle detection signal E1 from the rotary encoders 44a and 44b
, E2 are fed back to the motor controller 51. The rotation direction and rotation speed N1 of each motor 42a, 42b,
The mutual relationship between N2 and the initial phases φ1 and φ2 is a factor that determines the form of weaving, its width, etc., as will be explained in detail in the next section.

(4) Details of beam deflection by mirror rotation FIG. 7 is an explanatory diagram for geometrically analyzing the periodic deflection of the laser beam LB by the first and second tilted mirrors 41a and 41b. Note that in the following, the rotation direction of the first and second tilted mirrors 41a and 41b is expressed by a vector RP (
"Clockwise CW" and "counterclockwise CCW" are defined based on the direction seen from the starting point ST side in FIG. 8).

First, in FIG. 7, each vector is defined as follows.

■ Vector a...first tilted mirror 41
A unit vector parallel to and opposite to the incident direction of the laser beam LB at a.

■ Vector b...first tilted mirror 41
A vector indicating the direction of reflection of the laser beam LB at a. Therefore, the vector (-b) in the opposite direction to the vector b is the laser beam L incident on the second tilted mirror 41b.
The vector is parallel to and opposite to the direction of incidence of B.

■ Vector c...second tilted mirror 41
A vector indicating the direction of reflection of the laser beam LB at b.

[0044]Vector m1...Unit normal vector of the mirror surface of the first tilted mirror 41a.

[0045]Vector m2...Unit normal vector of the mirror surface of the second tilted mirror 41b.

At this time, the first and second tilted mirrors 41
According to the law of light reflection at a and 41b,

0047
]

[Math 1]

[0048]

[Math 2]

The following holds true. However, "x" indicates a vector product, and coefficients k1 and k2 are normalization coefficients for setting the lengths of vectors a and b to "1".

[0050] Therefore, from equations 1 and 2,

[0051]

[Math 3]

[0052]

[Math 4]

[0053] is obtained. However, "." indicates a scalar product.

Furthermore, if we substitute the number 3 into the number 4, we get

005
5]

[Math 5]

[0056] From the above, vectors b and c are given by vectors a, m1, and m2.

On the other hand, the vectors m1 and m2 are at angles Δθ1 and Δ from the rotation axis directions RA1 (FIG. 4) and RA2 (FIG. 5) of the respective rotor shafts 43a and 43b, respectively.
It rotates around the directions RA1 and RA2 while being tilted by θ2. Therefore, it can be determined based on Equation 5 how the temporal change in vectors m1 and m2 due to the rotational drive of motors 42a and 42b affects vector c. Although this analysis can be performed by simulation, a qualitative analysis will be performed below in order to clarify its basic properties.

As shown in FIG. 9, as the motor 42a rotates, the end point ME1 of the vector m1 becomes a circle MC1.
move above. Then, the second term on the right side of Equation 3 is vector F1
Then,

[0059]

[Math 6]

Vector F1 extends in the same direction as vector m1, and its length (vector a/vector m1) changes depending on the relative angle between vector m1 and vector a. Since the vector a is a constant vector, the end point of the vector F1 rotates periodically on the ellipse EL1. Note that there is also the first term on the right side of Equation 3, but since this is a constant vector as mentioned above,
Vector (−k
1 Move the end point of b) on the ellipse EL1.

Further, if the second term on the right side of Equation 7 obtained by transforming Equation 4 is vector F2, vector F2 has the same dependence as above on vector m2 and vector b. .

[0062]

[Math 7]

[0063]

[Math. 8]

Therefore, when considering the vector b as fixed, the end point of the vector (k1 k2 c) is another ellipse E.
L2 (not shown in FIG. 9).

A diagram schematically showing such a situation is shown in FIG.
It is. That is, the vector a is converted into a vector (k1 b) by reflection on the first tilted mirror 41a, and this vector (k1 b) is converted into a vector (k1 k2 c) by reflection on the second tilted mirror 41b. Each transformation is represented by a point on the ellipses EL1 and EL2. Note that the following analysis is about vector (k1 k2 c), and the length of this vector (k1 k2 c) is different from vector c, but what we need to find here is the direction of vector c and its length. This difference does not cause any problems.

With the above preparations, reference will be made to FIGS. 11 to 14. However, these figures are based on the ellipse EL1 shown in FIG.
, EL2 is conceptually shown as a two-dimensional schematic diagram. Further, a black circle indicates the end point of the vector (-k1 b), and a white circle indicates the end point of the vector (k1 k2 c). The reason why a plurality of ellipses EL2 are drawn around the ellipse EL1 in each figure is because the center of the ellipse EL2 changes depending on the end point position of the vector (-k1 b).

FIG. 11 shows the first and second tilted mirrors 41
a and 41b rotate in the same direction (clockwise in the illustrated example), and their rotational speeds N1 and N2 are equal,
Moreover, the case where the phase difference Δφ given by Equation 9 is zero is shown. However, the phase φ1 is defined as zero when the black circle is at the top of the ellipse EL1, and the phase φ2 is defined as zero when the white circle is at the top of the ellipse EL1.
It is defined as zero when it is at the lower end of 2. In the case of the figure, even if the first and second tilted mirrors 41a and 41b rotate, the changes in the reflection angle due to the rotation cancel each other out, and the vector (
The end point (white circle) of k1 k2 c) does not move from the same point.

[0068]

[Math. 9]

FIG. 12 shows a case where the phase difference Δφ is a finite value (other conditions are the same as in FIG. 11), and the locus of the end point of the vector (k1 k2 c) in this case is an ellipse EL.
It is a. When the phase difference Δφ is varied, the size of the ellipse ELa as the locus of the white circle changes.

On the other hand, FIG. 13 shows that the first and second tilted mirrors 41a and 41b rotate in opposite directions (clockwise and counterclockwise), and their rotational speeds N1 and N2
are equal and the phase difference Δφ is zero. At this time, the end point of the vector (k1 k2 c) reciprocates on the line segment LNa.

FIG. 14 shows a case where the phase difference Δφ is a finite value (other conditions are the same as in FIG. 11), and in this case, the end point of the vector (k1 k2 c) is the line segment LNb.
reciprocate above. Note that the line segments LNa and LNb are different in direction and length.

In addition, in FIGS. 11 to 14, the ellipse EL1,
Although the size and direction of the ellipse EL2 are drawn as being the same, the angles θ1, θ2, Δθ1, and
Their size and directional relationship vary depending on the magnitude of Δθ2. However, the properties shown in FIGS. 11 to 14 are held even in such general cases. As mentioned above, the direction of the vector c is the vector (k1
Since the direction of k2 c) is the same, these properties in the example can be generalized as follows.

■ First and second tilted mirrors 41a,
41b rotate in the same direction at the same rotation speed, the end point of the vector c moves on an ellipse, and the size of the ellipse changes depending on the phase difference Δφ.

■ First and second tilted mirrors 41a,
41b rotates in opposite directions at the same rotation speed, the end point of the vector c reciprocates on the line segment, and the length and direction of the line segment change depending on the phase difference Δφ.

The results of the above qualitative considerations have also been confirmed by computer simulation using Equations 3 and 4.

FIG. 15 shows an example of a simulation result for rotation in the same direction, in which the end point of vector c moves on an ellipse. Further, the size of the ellipse changes depending on the phase difference Δφ.

FIG. 16 shows an example of a simulation result for rotation in the opposite direction. The locus of the end point of vector c is a line segment, and its length and inclination angle Δψ change depending on the phase difference Δφ.

Note that the laser beam LB is transmitted through the parabolic mirror 36 (
After being reflected in FIG. 1), it is irradiated onto the workpiece, and the change after reflection has the same properties as above. Therefore, when the first and second tilted mirrors 41a and 41b are rotated while moving the laser torch 7 in the direction B along the abutting portion 23 in FIG.
Two modes can be selectively used as the locus of the laser beam LB on the laser beam LB.

One of them is the spin mode shown in FIG. This mode uses the first and second tilting mirrors 4
This is achieved by rotating the torches 1a and 41b in the same direction, and the torch 7
On the other hand, the laser beam LB spins on an ellipse. That is, the torch 7 is moved in the direction B along the abutting portion 23 (FIG.
), the trajectory of the laser beam LB becomes spiral. Pitch P1 (
(hereinafter referred to as spin pitch) is the rotational speed N1 (=N2
) and the moving speed of the torch 7. Further, the width W1 of the spiral locus (hereinafter referred to as spin diameter) changes depending on the rotational phase difference Δφ.

The other one is the scan mode shown in FIG. In this mode, the first and second tilted mirrors 41a,
This corresponds to the case where the torch 7 is rotated in the opposite direction.
On the other hand, the laser beam LB scans the line segment. That is, the trajectory of the laser beam LB when the torch 7 is moved in the direction B becomes a wavy trajectory. The pitch P2 (hereinafter referred to as scan pitch) of this wavy locus is the rotational speed N
1 (=N2) and the moving speed of the torch 7, and its width W2 (hereinafter referred to as scan width) changes depending on the rotational phase difference Δφ.

Therefore, when weaving welding the workpieces 21 and 22, the weaving mode should be selected from the above two modes, and command values for the rotational direction, rotational speed N1, N2, and rotational phase difference Δφ corresponding to the selected mode should be given. For example, weaving welding can be performed in a desired mode. Furthermore, if the rotational speeds N1 and N2 and the rotational phase difference Δφ are changed according to the moving direction of the torch 7, the torch 7
Even if the direction of movement changes, the spin diameter W1 and scan width W2 can be kept substantially constant.

These weaving operations can be performed at high speed since there is no need to swing the torch 7 itself. or,
Since it is not intended to rotate or swing the parabolic mirror 36, it does not increase the size of the vicinity of the torch 7 or complicate the mechanism.

(5) Other configuration example FIG. 19 shows another configuration example regarding the optical arrangement. In this example, in the laser oscillation unit 80, the first,
Second tilted mirrors 41a and 41b are provided. Therefore, the laser beam LB is periodically deflected before it is incident on the arm of the robot RB1. As a result, there is a fixed mirror 37 inside the elevating body 3.
, and an increase in the weight of the movable parts of the robot RB can be prevented.

(6) Mirror control method The rotational speeds N1 and N2 of the first and second tilted mirrors 41a and 41b
, rotational direction, and rotational phase difference Δφ,
It has been mentioned that the laser beam LB can be weaved in spin mode or scan mode. Next, a method of controlling the first and second tilted mirrors 41a and 41b for weaving the laser beam LB along a predetermined welding line on the workpiece in a predetermined mode will be described.

FIG. 20 is an explanatory diagram schematically showing the configuration of the optical system and the degrees of freedom of each drive section of the laser robot RB2, which has the same optical arrangement as the laser robot RB1 shown in FIG. 19. be. Here, the beam weaver 10 is a device in which a portion corresponding to the optical system excluding the laser oscillator 8 in the laser oscillation unit 80 in FIG. , 5). That is, the laser beam LB incident on the beam weaver 10
is sequentially reflected by the first and second tilted mirrors 41a, 41b and the fixed mirror M1, and then guided to the main body of the laser robot RB2. In this figure as well, the optical path of the laser beam LB shown in the figure corresponds to the optical path when the first and second tilted mirrors 41a and 41b are not rotated. Furthermore, the laser beam L
As described above, B is sequentially reflected by each of the fixed mirrors M2 to M4 provided inside the main body of the robot RB2, and is guided to the tip of the torch 7.

Also, in FIG. 20, as in FIG. 2, an absolute coordinate system xyz is set on the base 1, and the rotation angle around the rotation center axis z of the rotation column 2 is defined as the angle Θ, and the horizontal arm 4 is supported at the tip of the horizontal arm 4. The rotation angle of the first rotating body 5 around the axis Y is the angle α
The rotation angle of the second rotating body 6 around the axis V is expressed as an angle β.

As is clear from the figure, each mirror M2 to M4
itself is fixed and does not rotate. However, due to the rotation of the rotating column 2, the mirror M2 will also rotate at an angle Θ, and even if the laser beam LB emitted from the beam weaver 10 is not periodically deflected, the laser beam LB reflected by the mirror M1 will be mirrored. M2
The plane of incidence on the beam differs for each processing point. Therefore, the direction of reflection at mirror M2 also differs for each processing point. Similarly, the same thing happens for the other mirrors M3 and M4. That is, in determining the irradiation direction of the laser beam LB irradiated from the tip of the torch 7, in addition to the periodic deflection that the laser beam LB receives when passing through the beam weaver 10, the direction along the welding line of the torch 7 is determined. It is also necessary to consider the influence of the rotation of mirror M2 and the rotation of M3 and M4 due to the movement of the mirror M2. This means that the first and second tilted mirrors 41a and 4 in the beam weaver 10
In order to accurately control the motors 42a, 42b (not shown in this figure) of the motors 1b, it is necessary to rotate the mirror M2, rotate the mirrors M3, M
This means that the command values to be given to the motors 42a and 42b must be determined from information on the welding line, welding conditions, etc., including the influence of the rotation of the motors 42a and 42b. However, since the above effects are handled differently depending on the weaving mode of the laser beam LB, the spin mode and scan mode will be described separately below.

(i) Mirror control method when using spin mode In the spin mode shown in FIG.
is the welding line on the workpiece (corresponds to the butt part 23 in Figure 3)
Since the scanning is performed while drawing a spiral trajectory along the , there is no need to consider the influence of each of the mirrors M2 to M4 described above. Therefore, the command value for controlling the motors 42a and 42b is uniquely determined simply from information about the trajectory (spin diameter, etc.) and the moving speed of the torch 7.

FIG. 21 is an explanatory diagram schematically showing how the laser beam LB is scanned along the welding line l while drawing a spiral trajectory on the workpiece. Points Pi, Pi+1, and Pi+2 are taught machining points, and point Pij is one of the interpolated machining points, and in the figure, the torch 7 is just moving from point Pi to the next point Pi+1.
This shows the case where the

Therefore, if the magnitude of the welding speed of laser robot RB2 is expressed as speed v, spin diameter as symbol d, and spin pitch as symbol p1, then as mentioned above, in the spin mode, the first and second inclinations are Mirrors 41a, 41b
The rotation directions of the mirrors 41 and 41 are the same, their rotational speeds are also the same, and the spin pitch p1 is different from that of the first tilted mirror 41.
Since a is the distance that the laser beam LB scans over the workpiece during one rotation, the rotational speeds N1 and N2 of both mirrors 41a and 41b are as follows.

[0091]

[Math. 10]

It is represented by:

Furthermore, the rotational phase difference Δφ is approximately expressed as Equation 11.

[0094]

[Math. 11]

Here, the symbols Δθ1 and Δθ2 are the inclination angles of the first and second tilted mirrors 41a and 41b (see FIG. 5), respectively, and the symbol f0 is the mirror M4 (corresponding to the parabolic mirror 36 in FIG. 19). , which is treated as a constant here. Therefore, the value of the rotational phase difference Δφ is uniquely determined by specifying the spin diameter d.

Therefore, below, the derivation of Equation 11 will be explained. For this purpose, the first and second tilted mirrors 41a and 41b must be placed in an ideal state where they are sufficiently separated from each other so that the angles θ1 and θ2 of both mirrors can be considered to be almost zero. Assume that Under this assumption, the first and second tilting mirrors 4
The trajectories drawn by the laser beams LB reflected by each of 1a and 41b can be considered to be circular.

Under these conditions, the laser beam LB
FIG. 22 shows the trajectory of . In addition, in FIG. 22, in order to simplify the discussion, the inclination angle Δ of both mirrors 41a and 41b is
Assuming that θ1 and Δθ2 are equal,
As already mentioned.

In the figure, a circle C0 indicates the locus drawn by the laser beam LB reflected by the first tilted mirror 41a, and the circle C0 is the vector (-k1 b) shown in FIG.
corresponds to the trajectory drawn by the end point of . Therefore, when the rotational phase of the first tilted mirror 41a is 0, the first tilted mirror 41a
If the position on the trajectory of the laser beam LB reflected by a is a point O1, the trajectory drawn by the laser beam LB reflected by the second tilted mirror 41b is a circle C1. That is, when the rotational phase of the second tilted mirror 41b is also 0, the position on the trajectory of the laser beam LB reflected by the second tilted mirror 41b is point A1, and the second tilted mirror 41b The position on the trajectory of the laser beam LB reflected by the second tilted mirror 41b moves on the circle C1 depending on the delay or advance of the rotational phase of the second tilted mirror 41b.

When the rotational phase of the first tilted mirror 41a is the phase φ1 (the center O2 is the center of the laser beam L reflected by the first tilted mirror 41a), the circle C2 is
This is the trajectory drawn by the laser beam LB reflected by the second tilted mirror 41b at the position (position on the trajectory B). Therefore, the position on the trajectory of the laser beam LB when the rotational phase of the second tilted mirror 41b is 0 is the point A.
It becomes 2. Similarly, the position on the trajectory of the laser beam LB moves on the circle C2 depending on the delay or advance of the rotational phase of the second tilted mirror 41b. Similarly, a circle C3 indicates a trajectory that can be drawn by the laser beam LB reflected by the second tilted mirror 41b when the rotational phase of the first tilted mirror 41a becomes larger than the phase φ1, and the circle C3 indicates the trajectory that can be drawn by the laser beam LB reflected by the second tilted mirror 41b. is the position on the trajectory of the laser beam LB when the rotational phase of the second tilted mirror 41b is 0.

[0100] Therefore, the first and second tilted mirrors 41a
, 41b is 0, the trajectory of the laser beam LB reflected by the second tilted mirror 41b becomes a circle Cl with a center O and a radius OA1. The laser beam LB thus deflected so that its locus becomes a circle Cl is then focused by the mirror M4, and then
The workpiece is scanned and a spiral trajectory is drawn. That is, the radius OA1 of the circle Cl corresponds to the spin diameter d described above. Therefore, the spin diameter d0 when the rotational phase difference Δφ is 0 is

[0101]

[Math. 12]

It is expressed as:

Next, based on the above explanation, consider the case where the rotational phase difference Δφ between the first and second tilted mirrors 41a and 41b is not zero. Now, suppose that the rotational phase of the first tilted mirror 41a is 0 and the rotational phase of the second tilted mirror 41b is delayed by the phase Δφ with respect to the first tilted mirror 41a. The position on the trajectory of the laser beam LB reflected by the tilted mirror 41b is point B1 in the figure. Therefore, the locus drawn by the laser beam LB reflected by the second tilted mirror 41b is a circle with a center O and a radius OB1. At this time, the spin diameter d to be found is

[0104]

[Math. 13]

[0105]

In an actual robot, for convenience, the rotational phase difference Δφ is handled as shown in Equation 14, so if Equation 13 is expressed using Equation 14, Equation 15 can be obtained for the spin diameter d.

[0107]

[Math. 14]

[0108]

[Math. 15]

Therefore, if Equation 15 is calculated for the rotational phase difference Δφ, Equation 11 described above is obtained.

As described above, the first and second tilted mirrors 4 for weaving the laser beam LB in spin mode have been described.
The relational expressions and principles underlying the control methods 1a and 41b have been described. Next, steps for controlling the first and second tilted mirrors 41a and 41b in an actual robot based on the above principle will be described.

Prior to that, the configuration of the control system of the laser robot RB2 will be reconsidered based on FIG. 23. FIG. 23 is a block diagram showing the configuration of the control system. In the figure, all other devices except the teaching box 54 are connected to the robot controller 5 via a bus 56.
It is controlled by the command value of 2. The teaching box 54 is an input device for inputting teaching data as well as specified values of various welding conditions such as the spin diameter d to the robot controller 52. The robot controller 52 is composed of a CPU 52a and a memory 52b, and the memory 52b stores not only specified values sent from the teaching box 54 but also playback results calculated by the CPU 52a.

Based on the above preparations, next we will describe the control procedure for the laser robot RB2 for weaving in the spin mode.

FIGS. 24 to 26 are flowcharts showing the control procedure of the laser robot RB2.

First, in step S1, various parameters for weaving in spin mode are specified and input. That is, the specified values of the spin pitch p1, the spin diameter d, and the initial phase command value φ1 of the first tilted mirror 41a are input using the teaching box 54. These data are then stored in the memory 52b via the bus 56.

Next, in step S2, teaching is performed. As a result, the teaching data (coordinate value Xi of the absolute coordinate system of the teaching point Pi, coordinate value αi of the joint coordinate system) given by the teaching box 54 is stored in the memory 52b. Here, the number of teaching points Pi is assumed to be n (i=1 to n).

[0116] In step S3, the welding speed v at each teaching point Pi is
i is specified and input using the teaching box 54, and these data are stored in the memory 52b.

Next, in step S4, playback (interpolation calculation) is performed based on the teaching data in step S2. That is, the coordinate value Xij of the absolute coordinate system of the interpolation point Pij (the j-th interpolation point from the point Pi between the teaching points Pi and Pi+1) is calculated by the CPU 52a, and the coordinate value αij of the joint coordinate system is calculated by the inverse transformation. and is also stored in the memory 52b. Also, for convenience, the number of interpolation points Pij is assumed to be m (j=1 to
m).

Further, in step S5, initial phase command values φ1 and φ2 of the first and second tilted mirrors 41a and 41b are set.
(Note that the initial phase command value φ1 has already been given in step S1). That is, the CPU 52a reads the designated value of the spin diameter d from the memory 52b, and calculates
The rotational phase difference Δφ between both mirrors 41a and 41b is calculated based on . Then, from the calculated rotational phase difference Δφ and the initial phase command value φ1 of the first tilted mirror 41a read from the memory 52b, the initial phase command value φ2 of the second tilted mirror 41b is determined from equation 16,

[0119]

[Math. 16]

[0120] It is stored in the memory 52b.

[0121] Once the above preparations have been completed, the next step is to actually drive the laser robot RB2. That is, in steps S6 and S7, the tip of the torch 7 of the laser robot RB2 is moved to the first teaching point P1.
Move to. This is because the command signal Dx1 of the coordinate value α1 of the joint coordinate system of the first teaching point P1 stored in the memory 52b is given to the arm drive motor 55 by the robot controller 52, and as a result, each arm turns and rotates. This is achieved by moving. In order to generalize the following explanation, the first teaching point P1 is replaced with the teaching point Pi in step S6.

Next, in step S8, the first and second tilted mirrors 41a,
The rotational speeds N1i and N2i of 41b are calculated. That is, since the welding speed Vi has already been specified in step S3 for the teaching point Pi, the CPU 52a reads the necessary data from the memory 52b and determines the rotational speeds N1i and N2i from Equation 17.

[0123]

[Math. 17]

In step S9, the robot controller 52 sends to the motor controller 51 the rotation speeds N1i, N2i of the first and second tilted mirrors 41a, 41b, initial phase command values φ1, φ2, and Rotation direction command value DS (
A signal instructing the same direction) is sent, and the motor controller 51 converts the sent command value into motor drive powers D1i and D2i.
D2i is output to motors 42a and 42b, respectively. At this time, the robot controller 52 issues an ON signal to the laser oscillation device 8, and the laser beam LB oscillates. As a result, the laser beam LB has a power D
The first and second tilted mirrors 41a and 41b, which perform a predetermined rotational movement in response to the waves 1i and D2i, are periodically deflected so that their orbits become elliptical.

[0125] While maintaining this state, the tip of the torch 7 moves to the first interpolation point Pi1 (step S1
0, S11). That is, the command value Dxi1 of the coordinate value αi1 of the joint coordinate system of the interpolation point Pi1 is given to the arm drive motor 55 from the robot controller 52, and the torch 7 moves to the interpolation point Pi1 along the welding line l. As a result, the laser beam LB is weaved between the teaching point Pi and the interpolation point Pi1 in a spin mode. For convenience, step S10 is also performed for interpolation points.
In , the following explanation is generalized by replacing interpolation point Pi1 with interpolation point Pij.

Next, in step S12, the welding speed Vij at the moved interpolation point Pij and the rotational speeds N1ij, N2ij of the first and second tilted mirrors 41a, 41b are determined.
calculation is performed. Here, as a method for calculating the welding speed Vij at the interpolation point Pij, each teaching point P
Various methods can be used depending on whether linear interpolation is performed between i or a curve such as a parabola, etc.
Here, as an example, we will consider the case where two teaching points Pi and Point Pi+1 are interpolated using a curve SC as shown in FIG. Let us consider a case where welding speed Vij at each interpolation point Pij is determined. That is,
The welding speed Vij at one interpolation point Pij is
Assuming that the laser robot RB2 is set so that the travel time of the tip of the torch 7 between ij and Pij+1 is a constant value Δt, the interpolation point Pij and the next interpolation point Pij+
1 position vectors Xij and Xij in the absolute coordinate system
Using +1,

[0127]

[Math. 18]

It is given by:

Similarly, the welding speed Vij+1 at the next interpolation point Pij+1 is

[0130]

[Math. 19]

is given by, and the above procedure yields two points P
Welding speed V at all interpolation points between i and Pi+1
ij is required. However, the last interpolation point Pi
m, the interpolation point Pim and the next teaching point Pi
+1 position vector Xim, Xi in absolute coordinate system
Using +1,

[0132]

[Math. 20]

It is determined by:

[0134] Based on the above explanation, the discussion will now return to step S12. That is, the CPU 52a retrieves the interpolation point Pij and the next interpolation point Pij from the memory 52b.
+1 position data Xij, Xij+1 is read out, and formula 1
8, the value of the welding speed Vij at the interpolation point Pij is calculated. Further, the CPU 52a reads out the specified value of the spin pitch p1 from the memory 52b, and calculates the rotational speeds N1ij and N2ij at the interpolation point Pij using Equation 21.

[0135]

[Math. 21]

[0136] When the rotational speeds N1ij and N2ij at the interpolation point Pij are determined in the above manner, the motor drive power D1ij is determined by the same procedure as step S9.
, D2ij are applied to the motors 42a and 41b, respectively (step S13). and interpolation point P
When ij is not the last interpolation point Pim (step S
14), the tip of the torch 7 is moved again to the next interpolation point Pij+1 (steps S15, S11),
The laser beam LB is directed to the interpolation point Pij and the next interpolation point Pi.
Weaving is performed between j+1 in spin mode. Then, until the tip of the torch 7 reaches the last interpolation point Pim,
A series of procedures from step S11 to step S13 continues to be performed (step S14). As a result, the laser beam LB is applied between all interpolation points (points Pi1 to Pim).
is weaved along the welding line l while maintaining a predetermined spin pitch p1 and a predetermined spin diameter d.

Next, in steps S16 and S17, it is determined whether the next teaching point Pi+1 is the last teaching point Pn to which the tip of the torch 7 should move. That is, teaching point Pi+1 is teaching point Pn
If it is determined that this is not the case, the tip of the torch 7 moves to the next teaching point Pi+1 (step S7).
. Therefore, weaving welding is performed between the teaching points Pi and Pi+1 by the laser beam LB.

[0138] From then on, the last teaching point Pn
A series of steps are executed until the tip of the torch 7 reaches the point Pn (step S17), and when the tip of the torch 7 reaches the point Pn (step S18), weaving in the spin mode along the welding line l is performed. Welding is completed.

[0139] In the above explanation, the welding speed V
After determining the values of i and Vij, the rotational speeds N1i, N2i and N1ij and N2ij were determined, but the invention is not limited to this. For example, when linear interpolation is performed between each teaching point Pi, depending on the welding conditions, is the rotational speed N1 by approximating the welding speed Vi at all processing points to be equal.
, N2 may be calculated, or the rotation speed N1i may be calculated by approximating the welding speed Vij at each interpolation point Pij to be equal to the welding speed Vi at the previous teaching point Pi.
It is also possible to calculate j and N2ij.

(ii) Mirror control method when using scan mode On the other hand, in the scan mode shown in FIG. 18, as shown in FIG. 28, the beam spot SPi of the laser beam LB on the workpiece is always perpendicular to the welding line. (The direction of the beam spot SPi on the workpiece viewed from the processing point Pi on the welding line l corresponds to the vibration direction Σ of the laser beam LB). That is, in laser welding, the torch 7 is usually taught to be positioned perpendicularly to the work surface during teaching, which is a pre-process of laser welding. Further, the welding speed vector v of the torch 7 is a vector in the tangential direction of the welding line l. Therefore, it is considered appropriate to take the vibration direction Σ in a direction perpendicular to the vector v and the torch vector a0 parallel to the axis W of the torch 7 (taking the vector w in that direction). A conceptual diagram schematically showing such a situation is shown in FIG. 29, which shows the joint coordinate values Θ, α, β of the laser robot RB2 as well as the positional relationship of the torch vector a0 with respect to the processing point Pi.

Therefore, in order to always keep the torch vector a0 perpendicular to the vectors v and w, the mirror M
It is necessary to compensate for the effects caused by the rotation of M2 and the rotation of mirrors M3 and M4. That is, the control command values for each motor 42a, 42b are determined based on the welding conditions (welding speed, etc.), information regarding the welding line l (vector w), and the drive amount of each arm of the robot RB2 (angles Θ, α, β). More decisions need to be made.

[0142] However, the first and second tilted mirrors 41a,
The rotational speeds N1 and N2 of 41b at a certain time can be handled in the same way as in the spin mode. That is, using the welding speed vector v of the torch 7 and the scan pitch p2 at a certain time, the rotation speed N1,
N2 is

[0143]

[Math. 22]

It is expressed as [0144].

Next, we will consider what should be done to ensure that the vibration direction Σ of the laser beam LB is always in the direction of the vector w at the processing point Pi, taking into account the above-mentioned points. Note that this consideration ultimately corresponds to discussing a method of controlling the rotational phase difference Δφ between both mirrors 41a and 41b. For this purpose, it is essential to determine in which direction the laser beam LB should be deflected (vibrated) at the exit of the beam weaver 10. Therefore, it is necessary to track the change in the vibration direction of the laser beam LB from the processing point Pi toward the exit of the beam weaver 10.

First, as a simple case, if a laser beam LB vibrating in a certain direction is incident on an arbitrary rotating or rotating mirror Mi at an angle of 45 degrees, how will the direction of vibration change after reflection? In the following, we will discuss whether the change occurs in the cases shown in FIGS. 30 and 31 separately.

FIG. 30 shows a case where a laser beam IL vibrating on a straight line in the xi yi plane tilted by an angle θ from the xi axis is incident on a fixed mirror Mi. Here, as a coordinate system expressing the incident beam IL, the zi axis is the traveling direction of the incident beam IL, the xi axis is the direction perpendicular to the incident beam IL and the reflected beam RL, and the xi axis is the direction perpendicular to the incident beam IL and the reflected beam RL.
Let the yi axis be taken in the direction perpendicular to the axis and the zi axis. In addition, the coordinate system expressing the reflected beam RL is
x so that the zi+1 axis is taken in the traveling direction of the reflected beam RL.
As a coordinate system rotated 90 degrees around the i axis, xi+
1 axis, yi+1 axis, and zi+1 axis. If we define two coordinate systems like this,
The reflected beam RL vibrates on a straight line in the xi+1 yi+1 plane that is inclined by an angle -θ from the xi+1 axis.

On the other hand, FIG. 31 shows a case where the incident beam IL vibrating on the xi axis is incident on a mirror Mi rotating or rotating around the zi axis at an angle θr.
The coordinate system expressing the incident beam IL and the reflected beam RL is the same as in the case of FIG. 29. In this case, the reflected beam RL is tilted by an angle θr xi+1 yi+1
Vibrates on a straight line in a plane.

Therefore, a case combining the cases of FIGS. 30 and 31, that is, a laser beam L vibrating at an angle θ
When B is reflected by a mirror Mi that turns or rotates at an angle θri, the vibration direction θi (xi+1
Tilt angle from the axis: Hereinafter, this tilt angle will refer to the vibration direction of the laser beam LB. )teeth,

[0150]

[Math. 23]

It is given by:

Furthermore, the laser beam LB reflected by the mirror Mi is reflected by the next stage mirror Mi+1 (angle θri+1
If it is reflected again by turning or rotating,
The vibration direction θi+1 after reflection is

[0153]

[Math. 24]

It is clear that it is given by

From the above, in general, m angles θri
When a laser beam LB vibrating in a vibration direction Ψw is incident on an optical system consisting of a mirror Mi that rotates or rotates at , the vibration direction Ψ of the laser beam LB reflected by the final m-th mirror Mm is as follows. It can be seen that it is expressed by the number 25.

[0156]

[Math. 25]

[0157] Therefore, let us apply the above discussion results to the case of laser robot RB2. Here, FIG. 32 is an explanatory diagram showing the coordinate system of the laser beam LB that propagates while vibrating in the scan mode in the optical system of the laser robot RB2, and the arrangement of each coordinate system is as shown in FIG. 28 described above. This follows the method of defining the coordinate system. In addition, in the case of laser robot RB2, mirror M
1 neither turns nor rotates, so m = 4, θr in equation 20.
By substituting 1=0, the vibration direction Ψ is given. Therefore,
The vibration direction Ψ can be determined by rereading the angle θr2 as the angle Θ, the angle θr3 as the angle α, and the angle θr4 as the angle β.

[0158]

[Math. 26]

It is given by:

On the other hand, the aforementioned vector w is calculated by using the torch vector a0 and the welding speed vector v at a certain time,

[0161]

[Math. 27]

It is represented by: Here, the size of the torch vector a0 corresponds to the length l2 of the torch 7, and its direction is perpendicular to the direction of the welding speed vector v, so the size and direction of the welding speed vector v are Once determined, the vector w can be obtained from Equation 27.

Also, in FIG. 32, z is a coordinate system expressing the laser beam LB reflected by the mirror M4.
The 4 axis is parallel to the torch vector a0, and the y4 axis is parallel to the vector EF connecting the center E of the mirror M3 and the center F of the mirror M4.

[0164] Now, the coordinate values of point E and point F in the absolute coordinate system, that is, the vector e(xe , ye , ze )
and each component of the vector f (xf, yf, zf) (see Figure 29), it can be expressed as follows by the coordinate values (Θ, Y, Z, α, β) in the joint coordinate system. .

[0165] First, each component of vector e is expressed as
given by.

[0166]

[Math. 28]

[0167]

[Math. 29]

[0168]

[Math. 30]

[0169] Here, the constant Y0 is the offset amount.

Next, each component of vector f is expressed as vector EF
Since the size of is l1, each component of vector e and each

[0171]

[Math. 31]

[0172]

[Math. 32]

[0173]

[Math. 33]

It is given by the relationship: Therefore, the unit vector e0 in the y4 axis direction is

[0175]

[Math. 34]

The angle Ψ0 between the unit vector e0 and the vector w is given as (see FIG. 33):

01
77]

[Math. 35]

It is represented by: Therefore, the number 35 is changed to the number 3
If we transform using the relational expression 6, we get

[0179]

[Math. 36]

Equation 37 is obtained.

[0181]

[Math. 37]

[0182] Further, if we calculate Equation 37 for the angle Ψ0, we get

[0183]

[Math. 38]

[0184] is obtained, and the vibration direction Ψ to be found is:

0
185]

[Math. 39]

It is given by:

[0187] Therefore, the vibration direction Ψw of the laser beam LB emitted from the beam weaver 10 is expressed by Equation 26 and Equation 39.
Than,

[0188]

[Math. 40]

[0189]

As described above, the change in the vibration direction of the laser beam LB is tracked from the processing point Pi side toward the exit of the beam weaver 10, and as a result, the vibration direction Ψw of the laser beam LB at the exit of the beam weaver 10 is It has been shown that it is uniquely determined from the welding speed v determined from the coordinate values in the arm joint coordinate system at the processing point Pi and the coordinate values in the absolute coordinate system at the processing point Pi. Therefore, the relationship between the vibration direction Ψw of the laser beam LB and the rotational phase difference Δφ between the first and second tilted mirrors 41a and 41b will be considered.

Now, the coordinate system (xx, yy, z
z) and the vibration direction Ψw of the laser beam LB, as shown in FIG. That is, the first tilted mirror 41a is moved in the CCW direction, and the second tilted mirror 41b is moved in the CCW direction.
When rotated in the direction of W (see Figures 7 and 8) with a rotational phase difference Δφ, when the rotational phase difference Δφ is 0 degrees, the xx of the xxyy plane
The laser beam LB vibrates on the axis, and as the rotational phase difference Δφ increases, the vibration direction Ψw of the laser beam LB changes in the CW direction by an angle Δφ/2.

[0192] Therefore, the rotational phase difference Δ to be finally determined is
φ is

[0193]

[Math. 41]

It is given by:

FIG. 35 shows the flow for determining the rotational phase difference Δφ using the several equations obtained above for the scan mode. In the figure, *marks indicate absolute coordinate system values obtained from teaching data, **marks indicate joint coordinate system values obtained by playback, and numbers in parentheses indicate formula numbers.

The principle of the control method for performing weaving welding while satisfying predetermined welding conditions in scan mode has been described above.

[0197] Therefore, a flowchart showing the control procedure of laser robot RB2 based on the above principle is shown in Figs.
Shown in FIG. The control procedure for the laser robot RB2 in the scan mode is basically the same as the control procedure for the laser robot RB2 in the spin mode, and in the spin mode, the rotational phase difference Δφ is uniquely determined from the spin diameter d. On the other hand, in the scan mode, the only difference is that it is necessary to determine the rotational speeds N1 and N2 as well as the rotational phase difference Δφ for each processing point. That is, step SS8 and step SS13 in FIG. 37 correspond to the steps of calculating the rotational phase differences Δφi and Δφij at the teaching point Pi and the interpolation point Pij, respectively, and therefore the initial phase command values φ1i, φ2i and φ1ij, φ2ij, and the remaining steps The steps are shown in Figure 2.
The contents are the same as the corresponding steps in FIGS. 4 to 26. Therefore, here, the description of FIGS.
4 to FIG. 26, so the details will be omitted.

(7) Other Embodiments In the present invention, the number of tilted mirrors is not limited, and the periodic deflection of the laser beam is generally achieved by a combination of a plurality of tilted mirrors arranged in series in the optical path. realizable. Further, an optical system such as a fixed mirror may be included in the optical path between the plurality of tilted mirrors. Furthermore, it is also possible to use a common rotational power source for each tilting mirror and then rotate each mirror via a transmission. However, if the direct drive motor is provided individually as in the above embodiment, errors due to backlash etc. can be prevented.

[0199] Also, the first and second tilted mirrors 41a, 4
When the rotational speeds N1 and N2 of 1b are set to be different from each other, a deflection locus similar to a so-called Lissajous figure is obtained. Generally, if the ratio between the rotational speeds N1 and N2 is a rational number, a periodic deflection locus can be obtained. Also, the relationship between angle θ1 and angle θ2 and angle Δθ1
Various deflection trajectories can also be obtained by changing the relationship between and the angle Δθ2.

The light beam deflection system according to the present invention can be used not only for laser welding robots but also for laser robots that modify the surface of workpieces and equipment other than robots.

[0201]

[Effect of the invention] As explained above, in the invention of claim 1,
Periodic deflection is achieved by reflecting the laser beam while rotating multiple tilted mirrors. Since it is not necessary to provide these tilting mirrors and their rotation mechanisms at the tip of the arm, there is an effect that interference with obstacles due to an increase in the size of the tip of the arm can be prevented.

[0202] Furthermore, unlike a galvanometer mirror, the mirror is only rotated rather than oscillated, so that no drastic change in acceleration occurs along the direction of rotation. Therefore, it is possible to improve the periodic deflection speed, and
Synchronization control between each mirror is also easy, and the laser beam has the advantage of being highly controllable.

According to the invention of claim 2, the rotational speed of the plurality of tilted mirrors rotating in the same rotational direction and at the same rotational speed is determined from the moving speed of the torch and the spin pitch, and furthermore, the rotational phase difference is determined by the spin pitch. It can be uniquely determined from the diameter. As a result, it is possible to control a plurality of tilted mirrors so that the laser beam can be easily and accurately weaved in spin mode.

According to the third aspect of the invention, the rotational speed of a plurality of tilted mirrors having the same rotational speed and in which adjacent mirrors rotate in opposite directions to each other is determined from the moving speed of the torch and the spin pitch, and further, The rotational phase difference is determined for each processing point from the torch position information and arm drive amount. This results in
The effect on the deflection of the laser beam due to the drive of the arm can be compensated for, and the laser beam can be weaved in scan mode while always keeping the vibration direction of the laser beam tangential to the processing line and perpendicular to the center axis of the torch. This has the effect of controlling multiple tilting mirrors.

Furthermore, according to the fourth aspect of the present invention, it is possible to provide a module (light beam deflection device) capable of periodically deflecting a light beam. Further, this light beam deflection device is a device that can be applied to the laser robot according to claim 1, and has the effect of improving the deflection accuracy and deflection speed of the light beam.

Furthermore, according to the invention of claim 5, by making the rotation directions of the first and second rotating mirrors the same, it is possible to provide a light beam deflection device that can select the deflection locus of the light beam to the spin mode. There is.

Further, according to the invention of claim 6, there is provided a light beam deflection device in which the deflection locus of the light beam can be selected as a scan mode by making the rotation directions of the first and second rotating mirrors opposite to each other. There is an effect that can be done.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the optical configuration of a laser welding robot that is an embodiment of the present invention.

FIG. 2 is an external perspective view showing the mechanical configuration of a laser welding robot that is an embodiment of the present invention.

FIG. 3 is an explanatory diagram showing weaving welding by a laser welding robot that is an embodiment of the present invention.

FIG. 4 is a sectional view showing in detail the configuration of a first tilting mirror rotation mechanism.

FIG. 5 is a cross-sectional view showing in detail the configuration of a second tilting mirror rotation mechanism.

FIG. 6 is a control block diagram of first and second tilting mirror rotation mechanisms.

FIG. 7 is an explanatory diagram for geometrically analyzing periodic deflection of a laser beam by first and second tilted mirrors.

FIG. 8 is an explanatory diagram showing definitions of clockwise CW and counterclockwise CCW.

FIG. 9 is an explanatory diagram for analyzing the direction vector of a laser beam.

FIG. 10 is an explanatory diagram for analyzing the direction vector of a laser beam.

FIG. 11 is a two-dimensional schematic diagram for determining the reflection direction of a laser beam when the rotation direction, rotation speed, and rotation phase of the first and second tilted mirrors are the same.

FIG. 12 is a two-dimensional schematic diagram for determining the reflection direction of a laser beam when the first and second tilted mirrors have the same rotational direction and rotational speed, but different rotational phases.

FIG. 13 is a two-dimensional schematic diagram for determining the reflection direction of a laser beam when the first and second tilted mirrors have opposite rotational directions and the same rotational speed and rotational phase.

FIG. 14 is a two-dimensional schematic diagram for determining the reflection direction of a laser beam when the first and second tilted mirrors have opposite rotational directions, the same rotational speed, and different rotational phases.

FIG. 15 is an explanatory diagram showing an example of simulation results for rotation in the same direction.

FIG. 16 is an explanatory diagram showing an example of simulation results for rotation in the opposite direction.

FIG. 17 is an explanatory diagram showing characteristics of spin modes obtained in Examples.

FIG. 18 is an explanatory diagram showing the characteristics of the scan mode obtained in the example.

FIG. 19 is a schematic diagram showing the optical configuration of a laser welding robot according to another embodiment of the present invention.

20 is an explanatory diagram schematically showing the configuration of an optical system and the degree of freedom of each drive unit of the laser robot having the same optical arrangement as the laser robot shown in FIG. 19; FIG.

Figure 21 shows how the laser beam is scanned along the welding line while drawing a spiral trajectory on the workpiece.
It is an explanatory view shown typically.

FIG. 22 is an explanatory diagram showing a trajectory drawn by a laser beam when the first and second tilted mirrors are placed in an ideal state.

FIG. 23 is a block diagram showing the configuration of a control system of a laser robot.

FIG. 24 is a flowchart showing a control procedure of the laser robot in spin mode.

FIG. 25 is a flowchart showing a control procedure of the laser robot in spin mode.

FIG. 26 is a flowchart showing a control procedure of the laser robot in spin mode.

FIG. 27 is an explanatory diagram showing a case where interpolation is performed using a curve SC.

FIG. 28 is an explanatory diagram schematically showing the relationship between a beam spot of a laser beam on a workpiece and a welding line.

FIG. 29 is an explanatory diagram schematically showing the positional relationship of a torch vector to a processing point.

FIG. 30 is a schematic diagram illustrating a change in the vibration direction when a laser beam vibrating on a straight line with an inclination θ is reflected by a fixed mirror.

FIG. 31 is a schematic diagram illustrating a change in the vibration direction when a laser beam vibrating on the xi axis is reflected by a rotating or rotating mirror.

FIG. 32 is an explanatory diagram showing a coordinate system determined to express the vibration direction of a laser beam that propagates while vibrating in a scan mode within the optical system of a laser robot.

FIG. 33 is a schematic diagram showing the positional relationship between the unit vector e0 and the vector w.

FIG. 34 is an explanatory diagram showing a coordinate system determined to express the vibration direction of a laser beam propagating within the beam weaver.

FIG. 35 is an explanatory diagram showing a flow of determining a rotational phase difference in scan mode.

FIG. 36 is a flowchart showing a control procedure of the laser robot in scan mode.

FIG. 37 is a flowchart showing a control procedure of the laser robot in scan mode.

FIG. 38 is a flowchart showing a control procedure of the laser robot in scan mode.

FIG. 39 is an explanatory diagram showing each weaving method.

[Explanation of symbols]

7 Torch 8 Laser oscillation device 40a First tilted mirror rotation mechanism 40b Second tilted mirror rotation mechanism 41a First tilted mirror 41b Second tilted mirror 42a Motor 42b Motor LB Laser beam RB Laser robot RB1 Laser robot RB2 Laser robot RA1 Rotation axis of the first tilted mirror RA2 Rotation axis l of the second tilted mirror Weld line N1 Number of rotations of the first tilted mirror N2 Number of rotations of the second tilted mirror Δφ Rotational phase difference

Claims (6)

[Claims] 1. A laser beam is propagated along an arm, and a torch provided at the tip of the arm irradiates the workpiece with the laser beam while moving the torch along a machining line on the workpiece. In a laser robot that performs processing, (a) a plurality of tilted mirror rotation mechanisms that rotate a plurality of tilted mirrors tilted from a plane perpendicular to the rotational axis around their respective rotational axes are arranged in series along the optical path of the laser beam; (b) sequentially reflecting the laser beam on each of the plurality of tilted mirrors while rotating the plurality of tilted mirrors around the respective rotation axis directions by the plurality of tilted mirror rotation mechanisms; A laser robot characterized in that the irradiation direction of the laser beam emitted from the torch is periodically deflected by irradiating the laser beam from the torch after being reflected. 2. The laser robot control method according to claim 1, wherein the plurality of tilted mirrors have the same number of rotations and the same direction of rotation, comprising: (a) The number of rotations of the plurality of tilted mirrors is determined by (1) the speed at which the torch moves along the processing line while performing the predetermined processing, and (2) the speed at which the torch moves along the processing line within one period of deflection of the laser beam. the step determined by specifying the distance to move along and (
b) determining a rotational phase difference between two adjacent tilted mirrors in the plurality of tilted mirrors by specifying a spin diameter of the laser beam emitted from the torch; (c) the step (a); (b) controlling the rotation of the plurality of tilting mirrors by applying a drive output according to the rotational speed and rotational phase difference determined in step (b) to the plurality of tilting mirror rotation mechanisms. How to control a laser robot. 3. The laser robot according to claim 1, wherein the rotation speed of each of the plurality of tilted mirrors is the same and the respective rotation directions of two adjacent tilted mirrors are opposite to each other. (a) The number of rotations of the plurality of tilted mirrors is determined by: (i) the speed at which the torch moves along the processing line while performing the predetermined processing; and (i) the speed of the laser beam. (b) determining a rotational phase difference between two adjacent tilted mirrors in the plurality of tilted mirrors; The processing is performed based on the positional coordinate value of the tip of the torch in an absolute coordinate system at the processing point on the line where the predetermined processing is to be performed, and (1) the drive amount of the arm for moving the torch onto the processing point. (c) applying a drive output according to the rotational speed and rotational phase difference determined in the steps (a) and (b) to the plurality of tilting mirror rotation mechanisms; A method for controlling a laser robot, comprising: controlling the rotation of a tilted mirror. 4. A device for periodically deflecting a light beam, the device comprising: (a) rotating first and second tilted mirrors that are tilted from a plane perpendicular to the rotation axis about their respective rotation axes; first and second tilted mirror rotation mechanisms are provided in series along the optical path of the light beam; (b) the first and second tilted mirror rotation mechanisms cause the first and second tilted mirrors to be rotated; While rotating the mirrors around their respective rotational axes, the light beam is directed to the first direction.
and a second tilted mirror to periodically deflect the light beam by sequentially reflecting the light beam. 5. The light beam deflection device according to claim 4, wherein the first and second tilted mirrors have the same number of rotations and the same direction of rotation. . 6. The light beam deflection device according to claim 4, wherein the first and second tilted mirrors have the same number of rotations and opposite directions of rotation. .