JP7239338B2 - Laser processing robot and tool coordinate system setting method - Google Patents

Description

The present invention relates to a laser processing robot and a tool coordinate system setting method.

2. Description of the Related Art Conventionally, a robot is known that performs processing such as welding or cutting a workpiece with a laser beam (see, for example, Patent Document 1). In Patent Document 1, a laser irradiation device is moved to a predetermined command position by the operation of a robot, the actual position of the laser irradiation position is measured, and a laser beam is detected based on the deviation between the command position and the actual position of the laser irradiation position. Correcting the irradiation position is described.
A method of aligning a probe with respect to a target position using a light-reflecting sphere and laser light has also been proposed (see, for example, Patent Document 2).

Japanese Patent Application Laid-Open No. 2018-024011 Japanese Patent No. 4664412

Six-point teaching using a jig is generally used as a method of setting one point on the tool of the robot as the TCP (tool center point). In the case of a processing tool, in six-point teaching, the reference point of the jig is placed at a predetermined position with respect to the robot, and the processing point of the tool (for example, the tip of the tool) is aligned with the reference point by the operation of the robot arm. be done.

In the case of remote welding in which the workpiece is irradiated with a laser beam from a position distant from the workpiece, there is no object such as the tip of the tool at the machining point, so it is difficult to use six-point teaching.
By attaching a member such as a bar to the laser processing head of the robot and arranging the tip of the member at the processing point, it is possible to set the TCP by 6-point teaching. However, in this case, it is difficult to set the TCP so as to exactly match the processing point due to the influence of mounting errors of members on the laser processing head.
A design value for the position of the processing point may be set in the TCP. However, since there is an error between the design value of the position of the working point and the actual position of the working point, it is also difficult to set the TCP so as to exactly match the working point.

One aspect of the present disclosure is a robot arm, a laser processing head attached to the tip of the robot arm that emits a laser beam, and a reflecting surface provided on the laser processing head and arranged outside the laser processing head. a detection unit that detects the laser beam specularly reflected to the laser processing head along the emission optical axis of the laser beam; a control unit that controls the robot arm and sets a coordinate system of the laser processing head; wherein the reflecting surface is a spherical surface or a polyhedral surface centered on a predetermined reference point, and specularly reflects the laser beam traveling toward the predetermined reference point along the emission optical axis of the laser beam, thereby controlling the control By operating the robot arm, the laser processing head is positioned at a position where the laser beam specularly reflected along the emission optical axis is detected by the detection unit, and the laser processing head is positioned. The direction of the exit optical axis is calculated based on the position and orientation of the tip of the robot arm in the aligned state and the position of the predetermined reference point, and based on the calculated direction of the exit optical axis A laser processing robot for setting the axis of the coordinate system of the laser processing head by using a laser processing head.

1 is an overall configuration diagram of a laser processing robot according to one embodiment; FIG. It is a figure explaining the relationship between the emission optical axis of a laser beam, and the reflected optical axis of the laser beam specularly reflected from the hemispherical reflecting surface to the laser processing head. FIG. 4 is a front view of the detection surface of the detection unit, and is a diagram for explaining positions of spots of reflected laser light on the detection surface. 4 is a flow chart showing a tool coordinate system setting method according to one embodiment. 4 is a flow chart showing a tool coordinate system setting method according to one embodiment. FIG. 10 is a diagram for explaining the operation of the robot arm in the TCP setting process; It is a figure which shows one structural example of the scanning part provided in a laser processing head.

A laser processing robot 1 according to one embodiment will be described below with reference to the drawings.
As shown in FIG. 1, the laser processing robot 1 places the focus F of the laser beam L on the work W, and performs remote processing such as welding or cutting on the work W with the laser beam L. As shown in FIG. The laser processing robot 1 includes a robot body 2 having a base 2a and an articulated robot arm 2b, a laser processing head 3 attached to the tip of the robot arm 2b and emitting a laser beam L, and a laser beam L provided in the laser processing head 3. A detection unit 4 that detects the laser beam L reflected to the processing head 3 , and a control device 5 connected to the robot main body 2 , the laser processing head 3 and the detection unit 4 are provided.

The robot main body 2 is, for example, a 6-axis vertical articulated robot. Robot body 2 may be any other type of robot commonly used in laser machining. The base 2a is fixed on the floor and supports the robot arm 2b. The robot body 2 includes a servomotor (not shown) for driving each joint of the robot arm 2b and an encoder (not shown) for detecting the rotation angle of each joint.

The laser processing head 3 is connected to a laser light source (not shown) via a cable 6 and emits laser light L supplied from the laser light source via the cable 6 . The laser beam L is converged on a focal point F outside the laser processing head 3 by a lens (not shown) in the laser processing head 3 . A focal point F is a processing point where the workpiece W is processed by the laser beam L. As shown in FIG. The position and posture of the laser processing head 3 are changed by the motion of the joints of the robot arm 2b, thereby changing the position of the focal point F three-dimensionally.

The detection unit 4 is, for example, a camera or a photodetector, and has a two-dimensional detection surface 4a. As shown in FIG. 2, the laser beam L specularly reflected from the reflecting surface 10a to the laser processing head 3 outside the laser processing head 3 (hereinafter referred to as the reflected laser beam L') is incident on the detection surface 4a. . For example, a partially reflective mirror 3a such as a half mirror is arranged on the optical path of the laser beam L inside the laser processing head 3 . Part of the reflected laser light L' returning along the optical path is separated from the optical path by the partially reflecting mirror 3a and enters the detection surface 4a.

The detection surface 4a is arranged so that the optical axis (reflected optical axis) A' of the reflected laser beam L' specularly reflected along the emission optical axis A by the reflection surface 10a is positioned at the center of the detection surface 4a. there is The emission optical axis A is the optical axis of the laser beam L emitted from the laser processing head 3 to the reflecting surface 10a. A reflected laser beam L' having a reflected optical axis A' deviated from the emission optical axis A does not enter the detection surface 4a, or enters a position deviated from the center of the detection surface 4a. In FIG. 3, the solid-line circle indicates the reflected laser beam L' specularly reflected along the emission optical axis A' or the strong light spot near the emission optical axis A', and the two-dot chain line indicates the emission light. A reflected laser beam L' specularly reflected along a reflected optical axis A' deviated from the axis A' or an intense light spot near the exit optical axis A' is shown. When the center of the spot coincides with the center of the detection surface 4a, the detection unit 4 detects the reflected laser beam L' specularly reflected along the emission optical axis A and also detects the diameter of the spot on the detection surface 4a. do.

The control device 5 includes a control unit 5a having a processor, and a storage unit 5b having RAM, ROM, nonvolatile storage, and the like.
A processing program for processing the workpiece W with the laser beam L is stored in the storage unit 5b. The control unit 5a causes the robot arm 2b and the laser processing head 3 to perform operations based on the processing program by transmitting control commands to the servo motors of the robot arm 2b and the laser processing head 3 according to the processing program.

In executing the machining program, the control unit 5a controls the position of the focal point F by controlling the operation of the robot arm 2b based on the world coordinate system Σw of the robot body 2 and the tool coordinate system Σt of the laser processing head 3. .
The world coordinate system Σw is a coordinate system fixed with respect to the base 2a.
The tool coordinate system Σt is a coordinate system that is fixed with respect to the laser processing head 3 and set with the emission optical axis A and the focal point F of the laser beam L as references. For example, the tool coordinate system Σt is a three-dimensional orthogonal coordinate system, the Z axis of the tool coordinate system Σt is set parallel to the emission optical axis A of the laser beam L, and the origin of the tool coordinate system Σt is set at the focal point F. be.

The tool coordinate system Σt is set, for example, when the robot is installed in a factory or the like, or when the laser processing head 3 is replaced. The storage unit 5b stores a tool coordinate system setting program for setting the tool coordinate system Σt. According to the tool coordinate system setting program, the control unit 5a causes the robot arm 2b, the laser processing head 3, and the detection unit 4 to perform an operation for acquiring information necessary for setting the tool coordinate system Σt. Based on this, the tool coordinate system Σt is set.

Next, the tool coordinate system setting work (tool coordinate system setting method) based on the tool coordinate system setting program will be described.
As shown in FIG. 2, a hemispherical reflecting member 10 is used for the tool coordinate system setting work. The reflecting member 10 has a convex hemispherical reflecting surface 10a and a circular bottom surface 10b connecting ends of the reflecting surface 10a. The reflecting surface 10a is a mirror that specularly reflects the laser beam L. As shown in FIG. The reflective surface 10a has a center of curvature P located at the center of the bottom surface 10b and a constant curvature. The laser light L traveling toward the center of curvature P is specularly reflected along the emission optical axis A at an arbitrary point on the reflecting surface 10a. The center of curvature P is used as a reference point for setting the tool coordinate system Σt.

The reflecting member 10 is arranged within the motion range of the robot arm 2b, and the reference point P is positioned at predetermined position coordinates in the world coordinate system Σw.
The reflecting member 10 is arranged at an arbitrary position within the operating range of the robot arm 2b, the position coordinates of the reference point P in the world coordinate system Σw are input by the user to the control device 5, and the input position coordinates are set in the tool coordinate system. It may be configured to be used by a configuration program.

The tool coordinate system setting operation includes a Z-axis setting process for setting the Z-axis of the tool coordinate system Σt shown in FIG. 4 and a TCP setting process for setting TCP shown in FIG.
As shown in FIG. 4, in the Z-axis setting process, the controller 5a operates the robot arm 2b so that the reflected laser beam L′ specularly reflected along the emission optical axis A is detected by the detector 4. The laser processing head 3 is aligned with the position where the laser processing head 3 is aligned (steps SA1 to SA4), the position and orientation of the tip of the robot arm 2b are calculated (step SA5), and the calculated Based on the position and posture of the tip of the robot arm 2b and the position of the reference point P, the direction of the exit optical axis A with respect to the tip of the robot arm 2b is calculated (step SA6). Based on this, the Z axis is set (step SA7).

Specifically, as shown in FIG. 2, the controller 5a moves the laser processing head 3 with respect to the reference point P so that the laser beam L is directed substantially toward the reference point P by operating the robot arm 2b. Position (step SA1). The position and posture of the laser processing head 3 at this time are set based on the design values of the laser processing head 3 .

Next, the controller 5a causes the laser beam L to be emitted from the laser processing head 3 (step SA2), and whether or not the reflected laser beam L′ specularly reflected along the emission optical axis A is detected by the detector 4. (step SA3).
When the laser beam L is correctly oriented in the direction of the reference point P (that is, when the reference point P is positioned on the extension line of the emission optical axis A), the laser beam L is reflected by the reflecting surface 10a along the emission optical axis. Specularly reflected along A. When the reflected laser beam L′ specularly reflected along the emission optical axis A is detected by the detection unit 4 (YES in step SA3), the control unit 5a proceeds to the next step SA5.

On the other hand, when the laser beam L is not precisely directed toward the reference point P, the laser beam L is specularly reflected along the reflected optical axis A' deviated from the emission optical axis A by the reflecting surface 10a. When the reflected laser beam L′ specularly reflected along the emission optical axis A is not detected by the detection unit 4 (NO in step SA3), the control unit 5a controls the laser processing head 3 by operating the robot arm 2b. The position and attitude are adjusted (step SA4), and steps SA2 and SA3 are executed again. The control unit 5a repeats steps SA4, SA2, and SA3 until the detection unit 4 detects the reflected laser beam L' specularly reflected along the emission optical axis A. FIG.

Next, the control unit 5a acquires the rotation angle of each joint of the robot arm 2b from the encoder, and calculates the position and orientation of the tip of the robot arm 2b in the world coordinate system Σw from the rotation angle of each joint (step SA5 ). The position of the tip of the robot arm 2b is, for example, the center position of the tip surface of the robot arm 2b.

Next, the controller 5a calculates the reference position of the laser processing head 3 from the calculated position and orientation of the tip of the robot arm 2b, and calculates the reference position from the reference position of the laser processing head 3 and the position of the reference point P. The direction of the exit optical axis A is calculated (step SA6). The reference position of the laser processing head 3 is the position of the representative point on the laser processing head 3 fixed to the tip of the robot arm 2b.
Next, the controller 5a sets the Z-axis of the tool coordinate system Σt in a direction parallel to the direction of the exit optical axis A (step SA7). For example, the control unit 5a sets the Z-axis on the emission optical axis A.

The controller 5a executes the TCP setting process following the Z-axis setting process.
As shown in FIG. 5, in the TCP setting process, the control unit 5a operates the robot arm 2b to detect the reflected laser beam L′ specularly reflected along the emission optical axis A detected by the detection unit 4. (steps SB1 to SB4), and calculate the position and orientation of the tip of the robot arm 2b with the laser processing head 3 aligned (step SB5), steps SB1 to SB5 are repeated with different postures of the robot arm 2b (step SB6), and the calculated position and posture of the tip of the robot arm 2b, the position of the reference point P, and the distance from the reference point P to the reflecting surface 10a are calculated. Based on the distance, the position of the focal point F with respect to the tip of the robot arm 2b is calculated (step SB8), and the TCP is set based on the calculated position of the focal point F (step SB9).

Specifically, the controller 5a operates the robot arm 2b to position the laser processing head 3 so that the laser beam L is directed substantially toward the reference point P and the focal point F substantially coincides with the reflecting surface 10a. (step SB1). The position and posture of the laser processing head 3 at this time are set based on the design values of the laser processing head 3 .
Next, the controller 5a causes the laser beam L to be emitted from the laser processing head 3 (step SB2). Then, the controller 5a detects the reflected laser beam L′ specularly reflected along the emission optical axis A by the detector 4 and controls the beam diameter of the reflected laser beam L′ detected by the detector 4 to be the minimum. (Step SB3).

As shown in FIG. 6, when the laser beam L is correctly oriented in the direction of the reference point P and the focal point F coincides with the reflecting surface 10a, the beam diameter of the reflected laser beam L′ is minimized and detected. The diameter of the spot formed at the center of surface 4a is minimized. When the reflected laser beam L′ specularly reflected along the emission optical axis A is detected by the detection unit 4 and the diameter of the spot on the detection surface 4a is the smallest, the control unit 5a determines YES in step SB3. ), and proceed to the next step SB5. The determination as to whether the spot diameter is the minimum is made, for example, by comparison with a predetermined threshold set based on the minimum value of the spot diameter measured in advance.

On the other hand, if the reflected laser beam L′ specularly reflected along the emission optical axis A is not detected by the detection unit 4, or if the diameter of the spot on the detection surface 4a is not the smallest (step SB3 NO), the robot arm 2b is operated to adjust the position and orientation of the laser processing head 3 (step SB4), and steps SB2 and SB3 are executed again. The control unit 5a repeats steps SB4 and SB2 until the detection unit 4 detects the reflected laser beam L' specularly reflected along the emission optical axis A and the diameter of the spot of the reflected laser beam L' becomes the minimum. , SB3 are repeated.

Next, the control unit 5a acquires the rotation angle of each joint of the robot arm 2b from the encoder, and calculates the position and orientation of the tip of the robot arm 2b in the world coordinate system Σw from the rotation angle of each joint (step SB5 ).
Next, as shown in FIG. 6, the controller 5a operates the robot arm 2b so that the laser beam L is directed substantially toward the reference point P and the focal point F is substantially coincident with the reflecting surface 10a. The laser processing head 3 is positioned at the position (step SB7). This changes the posture of the robot arm 2b. Then, the controller 5a repeats steps SB2 to SB5.
The controller 5a executes steps SB2 to SB5 in at least two postures of the robot arm 2b (steps SB6 and SB7), and calculates the position and posture of the tip of the robot arm 2b in at least two postures.

Next, the controller 5a calculates the position of the focal point F in each posture of the robot arm 2b. Specifically, the control unit 5a controls the position and orientation of the tip of the robot arm 2b, the position of the reference point P, and the distance from the reference point P to the focal point F on the reflecting surface 10a (that is, the radius of the reflecting surface 10a). ), the relative position of the focal point F with respect to the reference position of the laser processing head 3 in the world coordinate system Σw is calculated. Next, the control unit 5a calculates the position of the focus F in the tool coordinate system Σt from the relative positions of the focus F in the two postures (step SB8).
Next, the control unit 5a sets the origin of the tool coordinate system Σt and the TCP at the calculated position of the focal point F (step SB9). For example, the controller 5a sets the focus F to the origin of the tool coordinate system Σt and the TCP.

As described above, according to the present embodiment, the tool coordinate system Σt is set by setting the laser beam L emitted from the laser processing head 3, the convex spherical reflecting surface 10a having the reference point P at the center of curvature, and the reflecting surface 10a. A detector 4 is used to detect the reflected laser beam L' specularly reflected from the surface 10a. Then, the direction of the laser beam L can be accurately aligned with the reference point P so that the laser beam L faces the reference point P based on the position of the spot of the reflected laser beam L' on the detection surface 4a. As a result, the direction of the exit optical axis A can be accurately calculated, and the Z axis of the tool coordinate system Σt can be accurately set so that the Z axis is parallel to the exit optical axis A.

Further, based on the position and diameter of the spot of the reflected laser beam L′ on the detection surface 4a, the laser beam L is directed to the reference point P, and the focal point F is aligned with the reflection surface 10a. The position of the focal point F can be adjusted accurately by using the As a result, the position of the focal point F can be accurately calculated, and the TCP can be accurately set so that the TCP coincides with the focal point F, which is the processing point.

In the above embodiment, whether or not the focal point F coincides with the reflection surface 10a in the direction along the exit optical axis A is determined based on the diameter of the spot on the detection surface 4a. You may judge based on the brightness of a spot. In this case, it can be determined that the focal point F coincides with the reflecting surface 10a when the brightness of the spot at the center of the detecting surface 4a is maximized.

In the above embodiment, the Z-axis setting process is performed separately from the TCP setting process, but the Z-axis setting process may be performed within the TCP setting process. That is, through steps SB1 to SB4, the laser processing head 3 is positioned at a position where the reflected laser beam L' specularly reflected along the emission optical axis A is detected by the detector 4. FIG. Therefore, after step SB5, the direction of the Z-axis may be calculated using the position and orientation of the tip of the robot arm 2b calculated in step SB5.

In the above embodiment, the laser beam L used for setting the tool coordinate system Σt may be the laser beam used for machining the workpiece W, or may be a laser beam different from the laser beam for machining. good. For example, if the processing laser light is invisible light such as infrared light, visible laser light may be used to set the tool coordinate system Σt. The setting laser beam L is guided along the same optical path as the processing laser beam so as to be coaxial with the processing laser beam.
The position of the focal point of the laser light changes in the direction along the emission optical axis according to the wavelength of the laser light. Therefore, when laser light L having a wavelength different from that of the laser light for processing is used for setting the tool coordinate system Σt, in step SB8, the focal point of the laser light for processing is adjusted in consideration of the difference in wavelength. A position is calculated.

In the above-described embodiment, the laser processing head 3 may further include a scanning unit 7 that swings the laser beam L around the swing axis that intersects the emission optical axis A.
FIG. 7 shows a configuration example of the scanning unit 7 in the laser processing head 3. As shown in FIG. This scanning unit 7 is a galvanometer scanner having two galvanometer mirrors 7a and 7b. The oscillation axes S1 and S2 of the two galvanometer mirrors 7a and 7b are arranged at mutually twisted positions, and the laser light L oscillates in two directions according to the oscillation of the two galvanometer mirrors 7a and 7b. That is, the angle of the emission optical axis A of the laser light L changes by an angle corresponding to the swing angle of the galvanomirrors 7a and 7b.
Numerals 7c and 7d are motors for rocking the galvanomirrors 7a and 7b about the rocking axes S1 and S2, respectively. Reference numeral 7e is a lens for condensing the laser light L. FIG.

The scanning unit 7 can control the direction of the emission optical axis A of the laser light L with higher accuracy than the operation of the robot arm 2b. Therefore, the direction of the laser beam L with respect to the reference point P may be adjusted by the operation of the scanning unit 7 in addition to the operation of the robot arm 2b.
Specifically, the laser processing head 3 is positioned so that the laser beam L is directed substantially toward the reference point P by the operation of the robot arm 2b while the galvanometer mirrors 7a and 7b are arranged at a reference angle (for example, 0°). be done. Subsequently, the laser beam L is oscillated by the oscillation of the galvano mirrors 7a and 7b, and the oscillation angle of the laser beam L is set to the angle at which the reflected laser beam L' along the emission optical axis A is detected by the detector 4. adjusted.

In this case, the controller 5a calculates the adjustment amount of the swing angle of the laser light L from the swing angles of the galvanomirrors 7a and 7b, and the state in which the swing angle of the laser light L is not adjusted by the scanning unit 7 ( The state in which the laser processing head 3 is positioned at a position where the laser beam L specularly reflected along the emission optical axis A is detected by the detector 4 in the state where the galvanomirrors 7a and 7b are arranged at the reference angle). , the position and orientation of the tip of the robot arm 2b are calculated.

In the above embodiment, a hemispherical mirror is used as the reflecting surface 10a, but a reflecting surface 10a having another shape may be used.
For example, the reflecting surface 10a may be a partial spherical surface having a smaller solid angle than a hemispherical surface, and the center of curvature P serving as a reference point may exist outside the reflecting member 10 .
Alternatively, the reflecting surface 10a may be a polyhedral surface centered on the reference point P and composed of a plurality of flat surfaces. In this case, the laser beam L directed toward the reference point P is specularly reflected along the emission optical axis A at one specific point on each flat surface. The reflecting surface 10a may be any curved surface having such specific points.

In the above embodiment, the position of the focal point F in each posture of the robot arm 2b in the Z-axis direction is obtained by calculation. may be measured by other means. For example, the distance to the reflecting surface 10a may be measured by a laser distance measuring device provided on the laser processing head 3 while the focal point F is aligned with the reflecting surface 10a.

1 laser processing robot 2b robot arm 3 laser processing head 4 detection unit 4a detection surface 5a control unit 7 scanning unit, galvano scanner 10a reflection surface A emission optical axis A' reflection optical axis F focus, processing point L laser beam L' reflection laser Light P Reference point, Curvature center Σt Tool coordinate system

Claims (6)

a robot arm;
a laser processing head that is attached to the tip of the robot arm and emits a laser beam;
a detection unit provided in the laser processing head for detecting the laser beam specularly reflected along the emission optical axis of the laser beam from a reflecting surface arranged outside the laser processing head to the laser processing head;
A control unit that controls the robot arm and sets the coordinate system of the laser processing head,
the reflecting surface is a spherical surface or a polyhedral surface centered on a predetermined reference point, and specularly reflects the laser beam traveling toward the predetermined reference point along an emission optical axis of the laser beam;
The control unit
Aligning the laser processing head to a position where the laser beam specularly reflected along the emission optical axis is detected by the detection unit by operating the robot arm;
calculating the direction of the emission optical axis based on the position and orientation of the tip of the robot arm with the laser processing head aligned and the position of the predetermined reference point;
A laser processing robot that sets axes of a coordinate system of the laser processing head based on the calculated direction of the emission optical axis. The detection unit has a two-dimensional detection surface on which the laser beam specularly reflected along the emission optical axis is incident, and the detection surface is the laser beam specularly reflected along the emission optical axis. 2. The laser processing robot according to claim 1, wherein the optical axis is positioned at the center of said detection surface. 3. The laser processing robot according to claim 1 , wherein said laser processing head includes a scanning unit that swings said laser light around a swing axis intersecting said emission optical axis. The control unit
After positioning the laser processing head by operating the robot arm, by operating the scanning unit, the swing angle of the laser light around the swing axis is specularly reflected along the emission optical axis. Adjusting the angle at which the laser light is detected by the detection unit,
The direction of the emission optical axis based on the position and posture of the tip of the robot arm with the laser processing head aligned, the position of the predetermined reference point, and the swing angle of the laser beam 4. The laser processing robot according to claim 3 , which calculates . A method for setting a tool coordinate system of a laser processing head attached to the tip of a robot arm using a reflective surface, wherein the reflective surface is arranged outside the laser processing head and centered on a predetermined reference point. A spherical or polyhedral surface with
aligning the laser processing head at a position where the laser beam is specularly reflected along the emission optical axis by the reflecting surface by operating the robot arm;
calculating the direction of the emission optical axis based on the position and orientation of the tip of the robot arm with the laser processing head aligned and the position of the predetermined reference point;
setting an axis of the coordinate system of the laser processing head based on the calculated direction of the emission optical axis. 6. The tool coordinate system setting method according to claim 5 , wherein said reflecting surface is a convex spherical surface having a constant curvature and centering on said predetermined reference point.

Images