Electricity and Control November 2020

SENSORS + SWITCHES

Laser-line triangulation technology

The line triangulation method is an often underestimated sensing mode for monitoring presence, completeness, position, and similar tasks. In many applications, compact, intelligent light section sensors deliver results that are more precise and reliable than those delivered by other types of sensors. Line triangulation technology is unaffected by extraneous light and reliably detects objects with minimal contrast or no contrast to the background. Pepperl+Fuchs looks at the use of line triangulation technology in different industrial applications.

T he primary goals of all automation are high through- put and the elimination of downtime and scrap pro- duction. Therefore, an increasing number of sensors in production, processing and logistics applications ensure that the relevant requirements are met. They are used to check the presence, completeness and accuracy of sup- plied parts. Slides and components must be in the correct position and orientation to be filled, processed, or picked up by a robotic arm. Many of these typical detection tasks can be performed reliably and elegantly using line triangu- lation technology. Light section sensors combine all the required compo- nents in one compact device and are usually easier to pa- rameterise than 2-D vision sensors. They work on the prin- ciple of triangulation, using a projected laser line to detect height profiles and edge contours with high precision. The known distances and angles of the triangle formed by the light source, camera, and object are used to calculate the exact positions of all points along the line projected on the target object. Key advantages The use of a sharply defined laser beam provides some decisive advantages when compared to normal vision sensors. Light section sensors can clearly detect low- contrast objects and even zero-contrast objects. They require only differences in height to detect surfaces. And the light section method is more resistant to extraneous light and fluctuating lighting conditions. In 2-D vision

sensors, (unexpected) changes in lighting in particular can significantly reduce or completely disable detection performance, if daylight enters a window, for instance. When using vision sensors, the exposure time, arrange- ment of the device and, where necessary, external light- ing must always be precisely adapted to the conditions of the application. In contrast, the automatic exposure time control function with which light section sensors are ideally supplied is sufficient for the most applications. From the automotive industry… These properties support the use of high-performance laser-line triangulation sensors, such as the SmartRunner Matcher from Pepperl+Fuchs, in numerous applications in the automotive industry, packaging technology, logistics, and in mechanical and plant engineering. When manufacturing car bodies, it is critical to check that fixing elements such as rivets, screws, clips, and dum- my plugs are present and installed in the correct position. These small parts often differ only slightly from the back- ground and the contrast is very low. The light section solu- tion can easily overcome this challenge. The sensor detects height profiles regardless of colour and surface structure and issues a good or bad signal via the switching outputs, depending on the detection result. If the sensor is mounted on a robot arm, diverse elements or scenes can be verified using the same device. Only one sensor is required as it can store multiple detection profiles. Other applications in the automotive industry include checking anchorages on skids (skid bolts), checking the precision of sheet metal parts before welding, and check- ing whether anti-vibration pads are correctly glued in place. Laser-line triangulation technology ensures reliable detec- tion in all applications. Its function is not affected by extra- neous light, low contrast, or reflections. …to packaging The packaging industry also benefits from line triangulation technology. For instance, plastic trays with multiple com- partments are often used to package ready meals. These allow the main course and side dishes to be kept separate

The laser-line triangulation sensor is used for rotation detection for ready-meal trays.

18 Electricity + Control NOVEMBER 2020