ES2294968B1 - SYSTEM FOR MEASURING WOOD SPLASHES THROUGH A THREE-DIMENSIONAL LASER SCANNER. - Google Patents

Abstract

System for measuring wood chips using a three-dimensional laser scanner, which measures the chips in real time from the point cloud obtained by the laser scanner, using a set of specific image processing algorithms. The system consists of a vibrating feeder (A) that separates the chips from the sample taken for a correct measurement and a flat conveyor belt (D), whose direction of movement is indicated. In this measuring tape a laser beam (C-E), whose line of intersection with the plane of the tape is captured by a high resolution camera (B). The images captured by the camera are processed to obtain the main measurements (length, width, thickness) of the chips in real time. The system is of interest in paper pulp manufacturing industries from chopped wood.

Description

Measurement system for wood chips by a three-dimensional laser scanner.

Mastery of the technique

It has application in the industry of manufacture of paper pulp from chopped wood or other industry where the granulometry of incoming bulk material influence subsequent processes.

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Prior art

There are automatic measurement systems, based on optical media and image processing (Bergman, 1998). These systems do not use the laser as a light source, nor triangulation for exact measurement of thickness in each Sliver of a sample. Thickness is a critical parameter in Kraft papermaking processes.

BERGMAN, T. 1998. On-line chip analysis: New technology for an improved pulping process - Can increase pulp quality. Pulp and Paper Canada, 99 (12), 150,151.

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Explanation of the invention.

The title of the present invention refers to a system that allows the measurement of wood chips for The production of paper pulp in real time.

The system consists of a feeder vibrator (A) that separates the chips from the sample taken to a correct measurement and a flat conveyor belt (D), whose Direction of movement is indicated. In this measuring tape a laser beam (E), whose line of intersection with the plane of The tape is captured by a high resolution camera (B). The High resolution camera (B) and laser (C) form a certain angle to get the triangulation effect. The captured images by the camera are processed to obtain the main measurements (length, width and thickness) of the chips in real time, from of the point cloud obtained by the laser scanner, using a set of specific image processing algorithms for This application.

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The system consists of:

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Vision System, which in turn It has the following elements:

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The laser (C) with linear beam (E), which is the light source in this System.

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Camera (B), which captures the Images to process.

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"Frame grabber" card, which guarantees a correct image capture and takes care of the transmission of it to the PC memory for later indicted.

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The mechanical system allows optimal positioning and movement of chips according to The vision system needs. In this case, the system mechanical is based on a vibrating feeder (A) and a belt flat measurement (D). The vibrating feeder improves the physical separation of the chips, since for the good measurement of they must be separated from each other. Tape flat generates the necessary relative movement between the laser and the object to measure. The mechanical system also guarantees the position and Vision system stability.

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The electronic system consists of a pulse counter integral with the axis of the conductive drum of the measuring tape and generates the capture pulses for the system view. Each pulse produces an asynchronous reset in the chamber and A new measurement cycle begins.

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Custom software, which allows real-time processing of digital images obtained by the vision system to obtain the point cloud of each splinter or object from the point cloud of the chip set u objects that pass through the laser beam. When passing a group of splinters through the laser beam it deforms. Deformation of laser beam is easily captured, by having the laser a constant chromaticity and a high contrast with the rest of Elements of the image. In this way, once the system is calibrated a point cloud is obtained from a group of chips or objects. Next, it is necessary to individualize each of the  splinters or objects to determine their measurements. This is achieved through connectivity algorithms that determine that Pixel belongs to a certain splinter or object. Starting at splinter point clouds or individualized objects are extract the main measurements (length, width and thickness).

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Brief description of the content of the drawings

Figure one

Diagram of the measuring system, splinters accepted in the process fall on the vibrating conveyor (A), in where they are separated and then on the conveyor belt flat (D), whose direction of movement is indicated.

Preferred Embodiment

The preferred embodiment is based on the chip measurement system currently in operation in a pulp mill and consists of a feeder vibrating that achieves a separation of the set of chips or incoming objects to the measuring tape. This feeder vibrating is formed by a tray of 1500 mm long by 500 mm wide with eccentric drive.

The structure on the measuring tape that guarantees an angle between the laser beam (E) and the camera axis (B). The preferred angle is around 45º, but it depends on the object to measure. Increasing the angle increases the resolution of the system, but also the possibility of laser occlusion.

The measuring tape is a 2000 flat tape mm long by 500 mm wide. It is necessary to ensure a good flatness on the measuring tape by means of a sheet above the which will run the tape. In addition, the color of the tape so that the laser light absorption is the lowest possible. It is preferable to use a matte white tape.

For vibrating feeder drive and measuring tapes were used frequency inverters that adapt the system speed to the amount of chips or objects to measure.

The system was placed in such a way that the tape of measurement returns the measured sample to the process.

Claims (3)

1. System for measuring wood chips by means of a three-dimensional laser scanner that allows the individual measurement of each splinter within a real-time sample, characterized by using the laser as a light source and triangulating it with a high chamber resolution for the exact measurement of thickness, length and width in each splinter. 2. Procedure followed in claim 1 to obtain the measurements of each of the splinters of a shows, by means of a vibrating feeder (A) that separates the splinter set for individual measurement on the flat belt (D). 3. Procedure followed in claim 1 to obtain the individual measurements of each object or splinter after obtaining the point cloud from the splinter assembly or objects that pass through the laser beam (E) using an algorithm based on connectivity.