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ABSTRACT This study aims to investigate the influence of moisture contents and grouser heights on traction force exerted on different surfaces in the track-soil interaction system. A sandy loam was employed for acquiring the soil parameters, such as kc, kφ, n, C, Ca, δ, φ, and γ. These parameters were obtained through the mean of the bevameter technique. Moisture contents of the sandy loam were changed from low to high levels, which could be listed as 1.4%, 8.0%, 14.7%, and 22.2% at last. The direct shear and penetration tests were performed for each soil condition of the moisture content, respectively. The model of the single-grouser-shoe (track model) had a length of 9 cm, a width of 15 cm, and varied grouser heights from 0 to 15 cm with a 0.5 cm interval. Based on the calculation result, in general, the shearing force produced by the bottom surface always performs better than either the shear force on the grouser-tip surface or two lateral surfaces. Simultaneously, prediction results also show that the shearing forces were significantly influenced by the level of moisture content in the soil.

ABSTRACT Aiming at the low mechanization of paddy field weeding and lack of dedicated agricultural machinery for paddy field weeding in China, a self-propelled system of paddy field weeding machine was designed. The overall structure and working principle of self-propelled system were illustrated and analyzed. The interaction mechanism of wheel-soil during weeding was analyzed. The wheel-soil interaction model was established, then, wheel traction and surface flatness were selected as the evaluation indexes for discrete element simulation experiment. The steering performance, stability, and over ridge ability of self-propelled system were analyzed, and field experiment was carried out. The simulation experiment results show that the wheel traction is approximately 600 N and the surface flatness is less than 30 mm. The field experiment results show that the minimum turning radius of the prototype is 2,050 mm in paddy, overturning limit angle of the prototype is 36°, and maximum height over the ridge is 400 mm. The speed range of the weeding machine on the road and weeding operation was 0~16.20 km/h and the 0~5.40 km/h respectively. The weeder can meet the speed demands of weeding operation. The study results can provide reference for research and development of paddy field operation machinery.