The production of precision products depends on robot control systems knowing the location of the adhesive bonding head or welding head to the nearest millimeter at all times. This means the robot needs some sort of eye. Specialized sensors can perform this function, most of which operate on the principle of laser triangulation. A laser diode projects a line of red light onto the workpiece, from which the light is reflected at a specific angle before being detected by a camera. From the position of the light striking the camera chip, the position and distance of the sensor with respect to the workpiece within the coordinate system can be calculated.

Robots can change shape depending on their surroundings. (© 2019 EPFL/ETHZ)

The problem with such systems is shadowing, which limits the flexibility of existing sensors. They also restrict the freedom of movement of the robot systems and integrating them is very labor-intensive. The only way to measure height with conventional sensors is to mount them along the direction of processing. With these sensors, however, the robot is blind when it changes its direction of movement. Having to predefine the processing direction significantly limits the flexibility of the handling systems. The only alternatives are to use several sensors or additional axes — either of which, given today’s state-of-the-art technology, can sometimes cost more than the robot itself.

SensePRO is a compact sensor system that measures 15 centimeters in diameter and is equipped with specially developed image processing algorithms, providing a shadow-free, all-around field of view. The system generates a 360° measurement field, offering complete flexibility with regard to the direction of measurement. No matter where the robot moves, at least one laser line is always optimally positioned, supplying precise positional information to the camera. This approach solves the problem of shadowing of the laser light by components with complex shapes.

To operate over long periods in harsh production environments, the sensor contains a cooling module that utilizes either water or air. To enhance cooling, the optical bench on which the laser diodes and cameras are mounted has an internal cooling structure. Due to its highly complex shape, the only way to produce it is by 3D printing. This intelligent thermal management system extends the sensor’s service life. The sensor is designed to fit robots made by all leading manufacturers and no additional programming is required to integrate the new sensor system into existing robot systems.

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