Power consumption and performance of a maize thresher with automatic gap control based on feed rate monitoring

Abstract

The threshing gap of a maize combine harvester has to be adjusted in real-time based on different feed rates if it is to achieve adequate threshing efficiency and avoid excessive power consumption. A threshing unit with automatic threshing gap control system based on the feed rate was developed using an electric-hydraulic to overcome these problems. The optimal control model of feed rate and the threshing gap was established for the control system: When the feed rates were 6, 8, and 10 kg s −1 , the optimal threshing gaps were 43, 47, and 51 mm, respectively. Taking a constant threshing gap (50 mm) as the control group, the operational performance of the automatic control system of the threshing gap was evaluated. The results showed that the detecting accuracy of the control system was within tolerance ±1.33%. The threshing efficiency of the threshing unit with the control system was higher than that of the threshing unit using a constant threshing gap when the feed rate fluctuated randomly. Compared with the control group, the average power consumption of the control system increased by 3.45%, but the average threshing efficiency increased by 7.32%, the broken grain rate decreased from 5.21% to 3.85%, and the grain-entrainment loss rate decreased from 0.29% to 0.21%. Thus, it can be seen that corresponding to different feed rates conditions, a proper threshing gap in the threshing unit with the developed automatic control system could obtain better working quality than with a constant threshing gap. • Fluctuation in the feed rate requires proper threshing gap control. • Proposed control system effectively significantly improved threshing efficiency. • Provides a theoretical basis to optimise threshing performance.