Tendertips
Special Problems
Display on a supermarket shelf. The asparagus is standing in water in refigerated storage. This upright display improves shelf life (click to enlarge).
After harvesting the asparagus plants are left to grow. The asparagus is a perennial vegetable and plants will grow productively for up to fifteen years (click to enlarge).
The asparagus harvesting and packing season is very short, and very intensive. It runs from September to Christmas, and the packhouses operate up to sixteen hours per day. There is thus almost zero opportunity to implement changes during the season. The long off-season of eight months appears to be a big advantage, since lots of work can be done, but this is offset greatly by the difficulty of testing the new developments. Only a full-on production run will reveal hidden weaknesses in the system, every bit of which must work. Off season testing is thus difficult if not impossible due to the unavailability of asparagus, and the cost of operating staff (who may well have other jobs).
To maximise the chances of new developments actually working in a production environment, the system was simulated using a software package, LABVIEW. A software simulation reveals many hidden pitfalls in algorithms, and the skill with which they have been programmed, but it cannot check the mechanical aspects of the system. However, LABVIEW is special in that it can hook-up to real-world devices, such as video cameras and control hardware. To make use of these features, a working asparagus sorting machine was built in the laboratory, controlled by LABVIEW to the new standards. A set of wooden “spears” was used, with inbuilt variation, and the image processing and sorting algorithms tested as thoroughly as possible.
