Image analysis – Histogram processing – For setting a threshold
Patent
1991-12-04
1994-07-12
Mancuso, Joseph
Image analysis
Histogram processing
For setting a threshold
36447407, 382 25, 348 88, 348142, G06K 900
Patent
active
053295978
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a device and a method for measuring a bending angle of a bent workpiece or a present bending angle of a workpiece under bending process, or an angle of a workpiece.
BACKGROUND ART
In the prior art, it is general than an instrument such as a square or a protractor is used for measuring a bending angle of a work sheet bent.
However, this method takes much time and causes an error for measuring due to a person who measures the angle. Further, this method prevents automation of the examining process notwithstanding a current of factory automation. Furthermore, this method prevents automatic determination of the final relative position of upper and lower dies thereby a desired bending angle is finally obtained after the present bending angle is detected during the bending process.
Such an automated bending processing is indicated in Japanese Patent 63-2687 (B) titled "A device for detecting bending angles of a work for a press brake", where a surface near the end of the work sheet is picked up by a visual sensor during bending processing, and the least bending angle of the work sheet is detected.
In the above patent, however, the bending angle is not obtained with high precision, because the sensor picks up the surface near the end part of the work sheet, at which generally a burr, warp, or taper exists. These obstacles make it difficult to detect an actual bending angle.
In particular, when a reflected light pattern is picked up at such an end part of the work sheet and when the end part is tapered, the image obtained from the reflected light is different from the actual light pattern since the reflected light has blurs. When a pickup device for light of permeability is used, a floodlight is required. In this case, the arrangements become bigger and therefore they are not used usually.
Furthermore, if the angle is detected at the end part, the composition of the frames of the bending machine would be limited since the position of the visual sensor is limited to the vicinity of the end part.
In addition, when the angle is detected at the end part, the angle detected is not representative one because the work is curved like a bow due to what is called "center flexure phenomenon."
DISCLOSURE OF INVENTION
The primary object of this invention is to solve the above problems and to provide a method and a device by which an representative bending angle of the work is detected with precision.
A further object of this invention is to provide a device for a bending machine to measure a bending angle quickly and precisely of a work sheet bent by the bending machine.
The method of measuring the angle formed by two surfaces of the work which has a V-shaped section as a whole or in part is proposed. In this method, light is so emitted to the two surfaces of the work as to induce a successive or intermittent linear light pattern on the surfaces; the pattern is picked up in a direction and projected on a coordinate plane as an image; then the linear light pattern picked up on the coordinate plane is processed, and inclinations of the light pattern with a coordinate axis of the coordinate plane are detected for obtaining the angle formed by the two surfaces.
The device for measuring the angle utilizes the method. The device includes a light emitting device for emitting light toward the two surfaces in order to induce a successive or intermittent linear light pattern on the surfaces, a pickup device for picking up the light pattern in a direction for projecting on a coordinate plane, an image processor for processing the picked up pattern and detecting inclinations of the pattern with a coordinate axis of the coordinate plane for obtaining the angle formed by the two surfaces.
This device is applied to a bending machine. In the bending machine, the light emitting device and the pickup device are attached to or near to a tool (punch and die), and the angle of the work sheet formed by the bending machine is measured by the angle measuring device. The light emitting and pickup device
REFERENCES:
patent: 4845764 (1989-07-01), Ueda et al.
patent: 4942618 (1990-07-01), Sumi et al.
patent: 5137362 (1992-08-01), LeBeau
Takano, Hidehiko, "Recognizing Techniques for Shape Patterns," The Information Research Party, pp. 31-32.
English Language Abstract of Japanese Document No. 59-197813.
English Language Abstract of Japanese Document No. 59-18408.
English Language Abstract of Japanese Document No. 59-160707.
English Language Abstract of Japanese Document No. 59-176611.
Japanese Search Report.
Aoki Takayuki
Kouno Hidehiko
Niwa Yoshiaki
Sengoku Akira
Amada Company Ltd.
Kouno Hidehiko
Mancuso Joseph
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