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 cm 3 .

Non-destructive technologies for fruit and vegetable size determination – A review

“…Fruit volume is calculated by summing the individual products of the cross-section areas multiplied by the helix pitch. Gall et al (1998), studying potatoes, reported CVs of less than 2.5% for tubers larger than 100 ml. Owing to the geometry of the system, errors were larger for smaller objects.…”

“…Another advantage of the artificial retina concept is that the photosensors used in this device are cheaper than any of the CCD or CMOS sensors equipped with video-cameras. A disadvantage of the artificial retina concept is that it cannot calculate fruit diameters, only fruit volume (Gall et al, 1998). The prototype artificial retina machine vision system developed by Kanali et al (1998) transferred the data obtained to a retina model, which was identical to the 'hardware' prototype.…”

Effect of orientation on the fruit on-line size determination performed by an optical ring sensor

“…Finally, in regards to the repeatability test, the reason for the lower repeatability of SVol (CV = 6.1% vs. CV = 2.1% for MALS) was the above-mentioned variation of the helix pitch involved in volume computation. The intrinsic lower precision of volume measurements with respect to major axis measurements (Gall, 1997;Gall et al, 1998;Moreda et al, 2005) would play a secondary role here.…”

“…3). The algorithms used in this research are listed in Gall (1997) and Gall et al (1998). The LED's emit infrared light in sequence around the ring with one switching cycle designated a scan revolution.…”

“…Due to the optical ring sensor own geometry and working method, the orientation of objects has a relevant effect on the accuracy of axes measurements (Gall, 1997;Gall et al, 1998). Authors of the research reported herein considered that quantifying this effect was interesting for purposes of assessing the commercial applicability of the system.…”