Sensors & transducers
Laser line scanners: the eyes of your robot
Robots are becoming increasingly independent and are able to tackle more complex tasks. Laser profile sensors play a crucial role in ensuring that robots move safely, as well as precisely guiding and locating their positions. The sensors act as the ‘eyes’ of the robot and are used in a variety of applications from gap measurement in car interiors and automatic weld inspection systems, to industrial pick-and-place systems, says Chris Jones, managing director of Micro-Epsilon UK
A
s well as inspecting one-dimensional parameters, there is now an increasing need for multi-dimensional quality
control in industrial production. Laser profile sensors (laser line scanners) are designed to carry out complex 2D/3D measurement tasks in robotics and other automated, high speed production environments, where the sensors are increasingly used to measure profiles and contours. The operating principle of a laser line scanner
is based on the laser triangulation technique for two-dimensional profile detection. They detect, measure and evaluate the profiles on different object surfaces. By using special lenses, a laser beam is enlarged to form a static laser line instead of a point and is projected onto the target surface. An optical system projects the diffusely reflected light of this laser line onto a highly sensitive sensor matrix. In addition to distance information (z-axis), the controller also uses this camera image to calculate the position along the laser line (x-axis). These measured values are then output in a two-dimensional coordinate system that is fixed with respect to the sensor. In the case of moving objects or a traversing sensor, it is therefore possible to obtain 3D measurement values. Laser line scanners are equipped with an integrated, highly sensitive receiving matrix that enables measurements on almost all industrial materials, largely independent of the surface reflection. The scanCONTROL series of laser line
scanners from Micro-Epsilon offers a number of technical advantages in robotics applications. Their compact, lightweight design with integral controller means the sensors can be mounted on robot arms and in locations on machines where space is limited. The sensor and integrated evaluation electronics are space-saving, which simplifies cabling. Measured data is generally
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available in real time and so can be used to automatically correct and control the production process.
Easy inTEgRaTion All scanCONTROL laser profile sensors are equipped with a Gigabit Ethernet interface for transferring profile data, as well as a multi- purpose connector for RS422, encoder input triggering, Digital In (HTL/TTL), power supply and synchronisation. The sensors support Power- over-Ethernet (PoE), which means they can be operated with only one cable, thus simplifying installation even further. A simple and intuitive configuration interface is provided with all sensors to allow sensor configuration, as well as full .SDK for more detailed machine integration. The sensors are configured with a unique IP address (user changeable), which enables future remote configuration and diagnostics. A Modbus protocol (supported via Ethernet and the RS422 interface) also enables direct connection between the sensor and a PLC. The SMART version of the scanCONTROL
series offers a ‘plug & play’ solution with integrated controller that is suitable for simple- to-complex measurement tasks, eliminating the need for any external controller or PC. Set up and configuration of the sensor is carried out via the scanCONTROL Configuration Tools PC software, which enables the measurement of steps, angles, seams and grooves. The parameter sets are stored in the sensor, which is why the sensor autonomously performs measurements without requiring any external control devices or PCs.
MEasUREMEnT of adhEsivE bEads on sMaRTphonEs A typical application for laser profile scanners is in the inspection of adhesive beads in
smartphones. The challenge here is the very fine contours inside the smartphone and extremely thin, semi-transparent adhesive beading. Here, absolute reliability and 100 per cent control of the completeness of the beading, the height and width of the applied adhesive are required. This also applies to logos on tablets and laptops: grooves are milled into the aluminium housing, in which the logo elements are glued afterwards. The latter must be flush with the housing. Haptics (i.e. touch sensation) is a critical factor, as the customer would immediately feel any protruding logo or depression. Using laser line scanners, these depressions are measured in order to determine the planarity as well as the depth. The parts being glued are also measured in order to ensure a perfect fit.
sTiTChing posiTion of CaR aiRbags Laser line scanners are also carrying out important inspection tasks in the automotive industry. For example, airbag covers on steering wheels should be functional and not impede the airbag, while opening during an accident. They also form part of the interior decor of the car. As interior parts, the covers must therefore harmonise with the overall appearance. The high aesthetic requirements placed on the cockpit, seats, interior trim and steering
February 2019 Instrumentation Monthly
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