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.

ABSTRACT A type of weeding device was designed to solve the problems of weeders in paddy fields, such as high rice seedling damage and low weeding rate. The structure of the weeding machine and the working principle are illustrated. The seedling avoiding and weeding mechanism of the weeding device were analyzed. The parts of the weeder that contacted the soil were designed. The contact process between the spring tine and soil in paddy was simulated using the discrete element method to study the change in mechanical behavior during the working process. To verify the performance of the weeding machine, the forward speed and hoeing depth were taken as experimental factors, and weeding rate and rice seedling damage rate were selected as test indices. Field experiments were conducted to study the effects of each factor on weeding operations. The results of the experiment were evaluated by multi-index comprehensive weighting. The test results showed that, when the forward speed was 0.30 m/s and hoeing depth was 40 mm, rice seedling damage rate was 3.4%, weeding rate was 85%. The weeding machine satisfies the requirements of weeding in paddy. This research can provide a reference for the design of intra-row weeding devices in paddy.