Development of a mechatronic control system for an autonomous self-propelled row-sowing seed drill to improve the quality of sowing operations on small plots

Abstract

The quality of row sowing on small plots in plant breeding and primary seed production is limited by the fact that commercial sowing machinery is designed for large fields and retains a mechanical drive of the metering units from the ground wheel. Wheel slip, passive terrain copying and short runs with frequent turns lead to a systematic deviation of the seeding rate, an increased scatter of placement depth and a violation of the joint inter-row width, while the agrotechnical tolerances for plots are stricter than for production fields. The study substantiates the structure of a mechatronic control system for an autonomous self-propelled seed drill, in which metering is tied to the true ground speed measured by an RTK satellite receiver together with odometry, the placement depth is stabilised by an active «sensor – linear actuator» loop, and the distribution uniformity is corrected by the signal of optical seed-flow sensors. Using the author's calculation model with segment-wise simulation of a run, the quality indicators of the baseline mechanical and the proposed mechatronic schemes are compared. Replacing the wheel drive with a servo driven by the true speed reduces the mean seeding-rate deviation from about 11% to within ±0.8% and removes its dependence on slip, which in the baseline reaches 16%. The root-mean-square deviation of placement depth decreases from 9.1 to 3.4 mm, bringing the indicator within the ±5 mm tolerance, while the cross-track deviation drops to 2.7 cm by the root-mean-square value. The obtained relations show that the gain in sowing quality on plots is achieved by reconfiguring the measuring-and-control loop of the already used working bodies rather than by complicating the metering system.