A ring sensor system for the determination of volume and axis measurements of irregular objects

Abstract

In agriculture, a large variability of objects in a range of sizes and shapes is found, leading to problems in size grading. For example, for a low-cost product such as potatoes, the predominantly used mechanical size-determining systems have errors of up to 30% and can cause damage, but they are cheap and have a throughput up to 20 tonnes per hour. Alternatives which can guarantee an improvement in accuracy and a financial gain for the companies are required. In this paper methods for the determination of volume and axis measurements using a simple ring sensor system are described. A modified co-ordinate system and the segmentation of the area between the ring and the object are used. The volume determination is independent of the direction of presentation of the objects. For the determination of axes, the objects must be presented in the longitudinal direction to allow the use of simple 2D algorithms. The accuracy of the system depends both on the number of transmitters and receivers placed on the ring and on its diameter. A small ring sensor system was developed, which can scan 3D objects in real time (36 000 potatoes, 3.6 tonnes per hour) with an accuracy of better than 5% for a volume larger than 100 .