Optimizing the working performance of a boat-type tractor using central composite rotatable design and response surface method

Abstract

Optimization of the structural and working parameters for a boat-type tractor is essential to improve the working performance and reduce the energy consumption of the agricultural machinery. To apply the central composite rotatable design and response surface method, the individual and interactive impacts of grounding pressure (X1), sliding speed (X2), depth of surface water (X3), curvature radius of the bow (X4), and grounding angle (X5) on the sliding resistance and subsidence depth of a self-designed boat-type tractor were assessed. An analysis of variance test indicated that the sliding resistance and subsidence depth were significantly sensitive to all independent variables except X4, and the contribution rates of a single factor on the sliding resistance and subsidence depth were ordered as X1 > X5 > X2 > X3 > X4. The terms X4X5 and X1X5 were the only significant factors (p < 0.05) that affected the sliding resistance and subsidence depth, respectively. Subsequently, the optimal combination of the structural and working parameters for the boat-type tractor on a specific soil was determined. The results suggested that the minimal sliding resistance was 150.71 N, which was obtained when X1, X2, X3, X4, and X5 were 265.2 kg m2, 0.52 m s−1, 2.35 cm, 454.01 mm, and 28.88°, respectively. To verify the working performance of the boat-type tractor with the optimized parameters, laboratory tests were performed on the hull model in soil bins. Using the original working parameters, the sliding resistance and subsidence depth were 165.2 N and 7.1 cm, respectively, which were accordingly optimized to 159.8 N and 6.7 cm with the optimal parameters. Consequently, the sliding resistance was reduced by 5.4 N (3.3%), and the subsidence depth was decreased by 0.4 cm (5.6%), indicating that the working performance of the boat-type tractor was greatly improved.