JPH0374323B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for automatically measuring the shape of each end of a steel pipe using an industrial robot, and particularly to a scanning locus of an optical gap sensor mounted on the robot.

The outer diameter, inner diameter, roundness, wall thickness, etc. of a steel pipe are important items that determine the quality of the steel pipe, and the shape of the groove is also important when the pipe end is beveled with the assumption that the pipes will be butt welded together. This is a quality evaluation item. Conventionally, these measurements have been performed manually using measuring jigs and instruments, but there are problems such as time-consuming, uneven measurement results, and monotonous work that makes it difficult to secure manpower. There is.

The present invention solves the above problems by having a robot perform such measurements, and by appropriately selecting the movement trajectory of the sensor attached to the robot, it is possible to measure the end face shape of steel pipes with high precision and quickly. That is. The method for automatically measuring the shape of a pipe end according to the present invention involves attaching an optical gap sensor to the tip of an articulated robot, controlling the position of the tip, and moving the sensor at a predetermined angle with respect to a vertical plane and a horizontal plane passing through the center line of the tube. four short first straight sections that radially cross the front end of the steel pipe along the two straight lines formed, a path that connects the inner and outer ends of the straight sections to form one continuous path, and the straight line. moving the sensor along a locus consisting of a short second linear section extending in the longitudinal direction of the steel pipe along the outer peripheral surface of the steel pipe from the outer end of the section, and operating the sensor on the first and second linear sections during this movement. The gap length between the sensor and the steel pipe is measured, and the pipe end shape such as the inner diameter, outer diameter, roundness, and groove shape of the steel pipe is determined from the measurement result and the known coordinate position information of the straight section. Next, this will be explained in detail with reference to examples.

FIG. 1 is a diagram illustrating the outline of the tube end shape measurement method of the present invention, and 10 is an articulated robot to which a sensor 20 is attached to the tip. The robot 10 has a pedestal part 1
2. A first arm 14 rotatably attached to the pedestal, a second arm 16 pivotally attached to the arm 14,
It consists of a third arm part 18 pivotally attached to the arm part 16, and can move the sensor 20 along a trajectory to be described later. The sensor 20 is an optical gap sensor that includes a laser light source 22 and a lens 2 as shown in FIG.
4, 26, a position sensor 28 made of a PNP semiconductor element, and a signal processing circuit 30. 34 is a UO steel pipe, and 36 is its welded part. 38 is a turning roller, a steel pipe 34
is rotated around its tube centerline.

To explain the operation of the gap sensor 20, when a narrowly focused laser beam 32 from the laser light source 22 is projected onto the surface of the steel pipe 34 via the lens 24,
The laser beam 32 is diffusely reflected on the surface. A dotted circle-like loop 32a schematically represents the intensity distribution curve of this diffusely reflected light. The lens 26 collects a portion of this diffusely reflected light and forms an image on the position sensor 28. When the steel pipe 34 retreats as shown by the dotted line, the position where the diffusely reflected light is generated also moves backwards, and at this time, the position where the lens 26 focuses the diffusely reflected light and forms an image on the position sensor 26 shifts as shown by the dotted line. . Because of this function, if the relationship between the image formation position on the sensor 28 and the distance between the sensor 20 and the object 34 is determined in advance, the distance can be determined from the image formation position. The imaging position is sensor 2
If it is at the center of 8, the current value flowing to the left and right is equal,
If the image is formed at a position shifted from the center of the sensor 28, a difference will occur in the current values flowing to the left and right. Signal processing circuit 30
detects the difference between the left and right current values, and calculates the distance by converting it into a gap distance.

FIG. 3 shows an example of the output of the gap sensor 20. The steel pipe 34 has a beveled end for butt welding, and a gap sensor 20 is disposed at the end of the steel pipe as shown in FIG. . Figure b shows the measurement output, with the vertical axis representing the sensor movement distance and the horizontal axis representing the distance between the sensor and the subject. As shown in the figure, such measurement results also indicate the shape of the tube end. Of the groove shape, the dimension d is called the root face width, and θ is called the bevel angle, which are measured from the measurement output shown in FIG. 3b. Note that the measurable gap length of the gap sensor 20 is not very large, so if the laser beam projection target of the sensor deviates from the pipe end and the gap becomes too large, measurement becomes impossible.

The present invention attempts to measure the tube end shape using such a sensor and robot, and FIG. 4 shows the movement locus of the sensor. Figure 4a is a perspective view, 3
4 is the steel pipe, and 40 is the locus. FIG. 4b shows the trajectory 40 seen from the tube end. As shown in these figures, the locus 40 has first straight line portions AE, BF,
CG, DH, and the parts AF, BG, CH, which connect the inner and outer ends of these straight parts to form a continuous path.
ED (this may be omitted), and second straight parts AI, BJ, CK, DL (K,
Although the position of L is hidden in the drawing, it is located at a position corresponding to I and J). In FIG. 4b, a chain line 42 indicates a horizontal plane passing through the center line of the tube, a chain line 44 indicates the same vertical plane, and dotted lines 46 and 48 are straight lines making an angle of 45° to these, and the first straight line portion of the locus 40 is the same. Dotted straight line 4
It's on 6,48. There is a slight gap between the tube end of the first straight section and the same between the second straight section and the outer surface of the tube. In addition, the first straight section includes a section hi from the inner end of the straight section to the inner surface of the steel pipe, a section ti corresponding to the thickness of the steel pipe, and a section from the outer end of the straight section to the outer surface of the steel pipe, as represented by AE. li (both indicate length; in this example, i=1)
Consisting of

In the present invention, a position command signal is given to the robot 10 to move the sensor 20 along such a trajectory 40, that is, as shown by the arrows E, A, I, A, F,
It is moved along the path B, J, B, G, etc., and the measurement is performed on the first and second straight line portions. Since the light emitting/receiving surface of the sensor 20 must be opposed to the subject, the robot can move the sensor along the first straight line and when moving the sensor along the second straight line. Now rotate the sensor 90°.
When such a measurement is performed, if the end face of the steel pipe is beveled as shown in Fig. 3a, the measurement result as shown in Fig. 3b will be obtained (however, in this case, the outer surface of the steel pipe will also be displayed as the measurement result). (effective for surface shape measurement, outer diameter measurement, etc.), while the position coordinates of the trajectory 40 are known on the robot 10 side. (Each point E, A, F...
Since the coordinate position of the robot is known from the robot position command signal or feedback signal, etc., the inner diameter, outer diameter, etc. of the steel pipe can be determined from the output signal of the sensor 20 as follows. That is, hi of BF, CG, DH is h ₂ ,
Assuming that h ₃ , h ₄ , and ti are t ₂ , t ₃ , t ₄ , and li are l ₂ , l ₃ , and l ₄ , the inner and outer diameters in the straight 46 directions are: Inner diameter = BG + h ₁ + h ₃ or outer diameter - t ₁ -t ₃ Outer diameter = AC-l ₁ - ₃ Similarly, the inner and outer diameters in the straight line 48 direction are Inner diameter = FH + h ₂ + h ₄ or outer diameter -t ₂ -t ₄ Outer diameter = BD-l ₂ - ₄ ti is The average value of the steel pipe thickness in the directions of straight lines 46 and 48 is (t ₁ +t ₂ +t ₃ +t ₄ )/4. If a large diameter steel pipe is placed horizontally, it will bend and the vertical surface 44
The inner and outer diameters are smaller than the inner and outer diameters at the horizontal plane 42. On this point, 45. In the pipe on lines 46, 48,
The outer diameter corresponds to the inner and outer diameters at the neutral point and shows the correct value. After measuring the inner and outer diameters on the 45° line as described above, rotate the steel pipe 45°, move the points on the top and bottom and on both left and right sides to the 45° line, and in this state reposition the sensor along the trajectory 40. 20 is moved (measured), and the above-mentioned constants are determined in 8 equal sections. These measurement results may vary or be averaged. By determining the major axis and minor axis from the measurement results, the roundness can be determined.

If the tube end is beveled, a result as shown in FIG. 3b is obtained, from which the root face width d and bevel angle θ can be easily determined. Note that the shape of the groove is not limited to that shown in the figure, but it is also possible to measure the shape of other shapes.

When measuring while moving the sensor along a trajectory 40 having a shape as shown in the figure, the shape can be measured by simply moving the sensor around the end of the steel pipe approximately once, and by moving the sensor along, for example, 45° lines 46 and 48. Measurements can be performed quickly without unnecessary passes in EG and HF, and the scanning span required from the robot's perspective is small. Furthermore, since this locus 40 consists of four pieces of the same shape (one of which is EAIF), the control can be simply repeated.

For steel pipe welds, it is important to understand the shape of the pipe end groove. FIG. 4c shows another embodiment in which a locus is added for grasping the shape of the groove on the tube end surface. A portion 40a of the trajectory 40 is a trajectory for measuring the shape of the weld groove, and is formed by arranging a plurality of first straight portions at a predetermined pitch and connecting them at their inner and outer ends. Although not shown, this locus 40 also has a second straight portion extending in the tube length direction. In this example, the path connecting the first straight line sections connects the inner ends and the outer ends of the first straight line parts. Even with this, measurements can be taken at four locations on the 45° line during approximately one rotation.
After completing the measurement in the state shown in Figure 4c, remove the steel pipe 34.
Rotate 45 degrees and measure again on the trajectory 40 excluding the portion 40a.

The measurement results of scanning at the trajectory portion 40a are shown in Fig. 3b.
The measurement outputs obtained are obtained for each of the seven lines, and the root face width d and bevel angle θ are measured for each line. In the embodiment, the first straight line has been described as a straight line that is at an angle of 45° to the horizontal or vertical plane passing through the center line of the pipe, but this is because the bending of the steel pipe is taken into consideration when inspecting the steel pipe. about 45°
This is because measurements are often made in the direction. but,
It goes without saying that the present invention is not limited to this angle.

As explained above, according to the present invention, the amount of movement of the robot arm end is small, and by simply repeating a predetermined pattern, it can change the outer diameter, inner diameter, roundness, thickness, bevel shape, etc. of the steel pipe by making almost one revolution. The shape of the end face can be measured accurately and quickly, resulting in significant effects such as saving labor in the inspection process, maintaining measurement accuracy, and reducing cycle time.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an overview of the measurement method of the present invention;
FIG. 2 is an explanatory diagram of the optical gap sensor, FIGS. 3 a and 3 b are explanatory diagrams and graphs showing the measurement procedure and measurement results by the optical gap sensor, and FIG. 4 is an explanatory diagram of the sensor movement locus used in the present invention. In the drawing, 10 is a robot, 20 is an optical gap sensor, 40 is a sensor movement trajectory, AE, BF, CG,
DH is the first straight part, AI, BJ, CK, DL is the second straight part, AF, BG, CH, DE or AB,
FG and CD are paths connecting the inner and outer ends of the first straight section.

Claims (1)

[Claims] 1. An optical gap sensor is attached to the tip of an articulated robot, and the position of the tip is controlled to move the sensor along two straight lines that make a predetermined angle to the vertical and horizontal planes passing through the center line of the tube. four short first straight sections that radially cross the front of the end; a path that connects the inner and outer ends of the straight sections to form one continuous path; The sensor is moved along a locus consisting of a short second straight section extending in the longitudinal direction of the steel pipe, and during this movement, the sensor is moved at the first and second straight sections to form a gap between the sensor and the steel pipe. Automatic pipe end shape, characterized by measuring the length and determining the pipe end shape such as the inner diameter, outer diameter, roundness, and groove shape of the steel pipe from the measurement result and known coordinate position information of the straight section. Measurement method.