When goods are delivered, towers of wire mesh boxes and pallets are transported out of trucks at loading bay height and placed on conveyor belts.
An automatic lifter moves the fork under the second package from the bottom and lifts it and all the packages on top of it. This allows the lower pallet or pallet cage to be discharged one at a time.
Since the number and height of the individual packages are unknown, the gap must be localized for the fork to move in.
The task was solved with a time-of-flight industrial camera (ToF camera). The compact, IP67-protected camera, with Sony Depth-Sense sensor and integrated IR LEDs, delivers 3D point clouds with fast recording times.
These point clouds are processed with our standard software VisionTools V60. The 3D data is converted into a 2D image with different grey levels according to the distance value for each pixel. A pattern-based recognition then finds the different geometries of wooden Euro pallets, plastic pallets, metal pallets and mesh pallets. The software sends the coordinates for threading the fork via an interface.
The advantage compared to a standard camera in this application is the independence of background, colouring and degree of contamination of the objects viewed. The additional 3rd dimension provides a high level of process reliability. Stickers or gaps in the filling of the grid boxes can lead to misinterpretations with a purely contrast-based 2D image.