Detailed Structure of the Weld Navigator Laser Vision Weld Seam ...

With the continuous development of manufacturing, the requirements for product welding technology are becoming increasingly demanding. In order to improve welding quality and reduce the labor intensity and working environment challenges for workers, welding automation has become an important direction. However, many welding tasks have unique challenges, such as easy deformation of workpieces or inconsistent joints, which complicate automated welding. The Weld Navigator seam tracking system was specifically developed to address these issues. Let's take a look at the structure of the laser vision seam tracking system.

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Laser Vision Tracking System Structure

The laser, acting as the structured light source, projects laser stripes onto the work surface below the sensor at a predetermined angle. The CCD directly observes the stripes on the surface under the sensor. The sensor is installed at a preset distance in front of the welding gun, enabling it to monitor the weld seam. During tracking, welding speed and forward viewing distance are used to calculate the delay time, ensuring that the welding gun follows the seam.

Laser Vision Sensor

The compact Weld Navigator laser vision sensor is typically installed on the side of the welding gun. The laser diode inside the sensor emits a visible laser beam, which is transformed into a fan-shaped light strip by the aperture, illuminating the workpiece. A CCD camera, set at an angle relative to the laser diode, captures the reflected light from the workpiece surface, forming an image of the joint's geometric profile on the CCD. Using optical triangulation, the system not only detects horizontal features but also determines the height between the sensor and the workpiece.

The sensor's function is to convert the measured physical quantity into a useful electrical signal that corresponds to the quantity, fulfilling the requirements for information processing and control. The control system analyzes the signal from the sensor and generates control signals. The actuator typically consists of a motor and cross slide, with the servo motor controlled by the control signals.

Image Preprocessing

In the welding robot vision system, image processing can generally be divided into two aspects: first, the enhancement, filtering, and binarization of the acquired raw images. The goal is to remove noise from the original image and make it clearer, with more prominent edge features—this is the preprocessing step. Second, the preprocessed image undergoes edge detection, feature extraction, and other operations to accurately obtain the center information of the weld seam for the robot's coordinate adjustments, ensuring welding quality.

In the study of real-time image processing methods for visual seam tracking, image enhancement is first applied to increase image contrast, followed by median filtering to remove image noise. Binarization is then used to extract the target image from the background. In post-processing research, key technologies for laser vision weld seam tracking system image processing, such as the extraction of the centerline of the weak light band and feature point detection, have been proposed with practical methods. The centerline extracted using the central axis transformation method is a continuous, single line. The slope analysis method is used to detect feature points in a convenient and reliable way. This processing method can accurately detect weld seam feature points, with fast processing speed, meeting the real-time requirements of the tracking system.

Operation of the Laser Vision Weld Seam Tracking System

The above content provides an analysis of the Weld Navigator laser vision seam tracking system's structure. Before the welding operation begins, the welding gun's position is adjusted to align with the center of the seam. Once the power is turned on, the system begins to operate. The program starts running, and the CCD in the sensor continuously monitors the image. The software triggers a timer, and based on the required welding speed, the time interval of the timer is adjusted. Every set interval, a snapshot of the image is taken, and the image is processed in real time by the program to find the weld seam's center. The deviation between the current seam center and the initial center is used as the detection value, and an adjustment value is sent to the robot controller. The controller then directs the robotic arm to guide the welding gun, achieving automatic tracking.

When do we need to equip the welding robot with laser vision?

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In arc welding, if the welding accuracy cannot be guaranteed to reach ±0.3mm, it is necessary to consider the use of laser positioning or laser tracking. To select a laser vision welding seam tracking system, you first need to verify whether it interferes with the tooling fixture, and secondly, consider whether it will affect the time beat. If both not, then the laser can be fully integrated into the robot workstation.

The basic inspection principle of laser vision welding seam tracking

The basic principle of laser seam tracking is based on the laser triangle measurement method. The laser emits line laser light to the surface of the workpiece, and after diffuse reflection, the laser contour is imaged on the CCD or CMOS sensor. The controller then processes and analyzes the collected images to obtain the position of the weld, which is used to correct the welding trajectory or guide the welding.

What is laser tracking?

Laser tracking uses a laser vision sensor to detect the weld in advance before the welding torch , , and calculates the position coordinates of the sensor measurement point through the pre-calibrated positional relationship between the laser vision sensor and the torch. During the welding process, the robot’s teaching position and the sensor’s position are calculated. The detection positions are compared, and calculate the position deviation of the corresponding point. When the welding gun lagging behind the laser line reaches the corresponding detection position, the deviation is compensated to the current welding trajectory to achieve the purpose of correcting the welding trajectory.

What is laser positioning?

Laser positioning is the process of using a laser sensor to make a single measurement of the position to be measured and calculating the position of the target point. Generally, when with a short welding seam or the use of laser tracking interferes the tooling fixture, the welding seam is corrected in the form of laser positioning. Compared with laser tracking, the function of laser positioning is relatively simple, implementation and operation It is also more convenient. However, since it is detected first and then welded, the positioning is not suitable for welding workpieces with severe thermal deformation and irregular welds that are not straight lines or arcs.

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