This Is AuburnElectronic Theses and Dissertations

Development of an Automated Planter for Sweet Potato Slips


Fluctuating oil prices and the urge to reduce oil dependency has significantly increased US ethanol production. In 2011, approximately 28% of the corn market was used for fuel ethanol production. The expanding ethanol industry will require alternative feedstocks. Sweet potatoes provide a viable ethanol feedstock producing 2-3 times the carbohydrates compared to corn. However, one major drawback is the cost associated with planting sweet potatoes which depends extensively on manual labor with transplanters commonly used. Automation of sweet potato planting could provide a means to reduce planting costs while increasing planting capacity (ac/h). The objectives of this research were to: 1) design and evaluate a mechanism to automatically sort and singulate sweet potato slips and pine seedlings; and 2) identify physical characteristics of slips and seedlings which limit sorting performance. This automated sorting system utilized a hook mechanism to extract slips or seedlings from the bottom of a holding bin. Experiments provided quantitative and qualitative analysis to evaluated rear baffle designs, hook entry angle, and a grasping mechanism. Experiments using seedlings evaluated hook design and the rate at which seedling funneled to the bottom of the bin. The mean sorting rate (the frequency slips or seedling were removed from the bin) and singulation rate (the percentage at which single slips or seedlings were removed from the bin when slips were extracted) were used to evaluate design. Qualitative results determined that a single, triangular shaped hook, 3.81-cm wide could effectively sort and singulate slips or seedlings. The bottom of the front and rear panels of the holding bin tapered together, the optimum angles to support slip or seedling feed were iii determined to be 51° and 46°, respectively to improve feed to the bin bottom. A two baffle system utilized a flat front along with a rippled rear baffle limited the volume of slips at the bottom of the bin and aided in slip feed. The flexible nature of slips required a grasping mechanism to physically secure slips prior to extraction, which ensured complete removal from the bin. Pine seedlings on the other hand had a larger diameter and were more rigid. Therefore, an open hook sorted seedlings more efficiently. The physical characteristics of slips and seedlings significantly affect the accuracy at which they could be automatically sorted. The highest sweet potato slip sorting accuracy was achieved projecting the grasping mechanism into the bottom of the bin at approximately 22.3°. This experimental setup yielded a sorting rate of 62.0% with 43.0% slip singulation. Pine seedling sorting performance was 49.0% with 51.0% singulation.