Abstract
Seed planters with the conventional ground wheel and chain-gear driven seed metering units suffer from several limitations, such as the inability to plant seeds at variable rates, high missing rates at faster travel speeds, and higher down-times due to the intricacy of the manual discs replacement procedure for planting a different type of crop seed. Therefore, an apt solution to overcome these significant limitations is to: (a) replace the ground wheel and chain-gear based disc driving mechanism with a drive-by-wire system that comprises motors and sensors for variable rate planting and (b) incorporate a two-level adjustment of the applied negative pressure in the vacuum chamber for two different types of seeds, and (c) design seed metering unit that can plant multiple types of crops without any use of multiple discs. This paper presents the design and working of a novel variable rate multi-crop pneumatic seed metering unit that addresses the limitations of conventional seed planters. Laboratory tests were carried out on our proposed metering unit for maize and soybean seeds at varying rates in compliance with travel speeds. Experimental evaluation of the developed metering unit was performed on a lab test bench in terms of accuracy, average miss counts, and average multiple counts at various rotational speeds. The experimental results proved that our developed multi-crop seed metering unit performed significantly better than the conventional seed metering units by obtaining the average miss-count of 5.4 seeds, average multiple-count of 2.5 seeds, and coefficient of variation in spacing (precision) of 0.34 inches for a set of travel speeds of 2 km/h to 4 km/h.