Submitted to: Biosystems Engineering
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/6/2009
Publication Date: 7/8/2009
Publication URL: hdl.handle.net/10113/42254
Citation: Lefcourt, A.M., Narayanan, P., Tasch, U., Kim, M.S., Reese, D., Rostamian, R., Lo, Y. 2009. Orienting apples for imaging using their inertial properties and random apple loading. Biosystems Engineering. 104(1):64-71. Interpretive Summary: The inability to develop a cost-effective method to control the orientation of apples has hindered use of machine vision to screen individual apples for quality problems such as bruising and food safety problems such as fecal contamination. We discovered that apples could be oriented simply by rolling apples down a track consisting of two parallel rails. As the rotation speed of the apples increased, the apples moved to an orientation where they rotated about the stem/calyx axis. However, in a prior test, apples that were loaded end-over-end onto the track often continued to roll end-over end, i.e., around an axis perpendicular to the stem/calyx axis. To test whether this loading condition was a practical problem, a new series of tests were conducted where apples were automatically loaded onto the test track with random initial orientations. Unfortunately, end-over-end rotation remained a problem for about 5% of the apples. Fortunately, the end-over-end problem was found not to be related to any specific apple characteristic. When apples that first rolled end-over-end were recycled and placed back on the track, 95% of the recycled apples did not roll end-over-end. As the overall orientation process and the end-over-end problem were both random, it was suggested that a commercial system could be constructed where apples that were not oriented properly were recycled. Such a commercial system is economically viable as the cost of the track system is much less than the cost of existing motor and gear based systems. Furthermore, a track based system would have no maintenance or operating costs. The theoretical results of this study demonstrate an interesting scientific principle related to rotation of axially symmetric bodies, while the practical results are of interest to designers of commercial fruit processing systems.
Technical Abstract: The inability to control apple orientation during imaging has hindered development of automated systems for sorting apples for defects such as bruises and for safety issues such as fecal contamination. Recently, a potential method for orienting apples based on their inertial properties was discovered. To test this method, apples were rolled down a track consisting of two parallel rails. As angular velocity increased, apples generally moved to an orientation where the stem/calyx axis was parallel to the plane of the track and perpendicular to the direction of travel. However, theoretical analyses and experimental results demonstrated that select initial loading conditions could prevent or impede this orientation process. In this study, the practical importance of initial loading conditions was tested using two different methods to randomly load apples onto the track. Replicate trials indicated that successful orientation at rates of about 80% for Red and Golden Delicious apples was random, and that only 5% of apples exhibited undesirable loading condition and imaging orientation. Results suggest that a commercially-viable orientation system could be developed by recycling apples that are not oriented during imaging, and that it should be possible to improve single-pass orientation rates by addressing track compliance issues.