Design and test of the skateboard support device for crawler float-type lotus root excavator

The lotus root is one of the most popular food products in the stem of the lotus plant in Asia areas. Mechanical excavators of lotus roots can be expected to save the cost and labor intensity. However, the existing track float self-propelled excavator cannot fully meet the large-scale production, due to the large overall weight. There are also some difficulties in climbing, turning, and slipping vehicles in the field. In this study, the skid support device was designed to treat the high driving resistance and excess sinking of the crawler float-type excavator of lotus root. The device was installed on both sides of the chassis and hydraulically driven up and down to adjust the position. The gravity of the whole machine was supported to reduce the grounding pressure and sinking depth of the crawler. The passability was also improved as well. The driving performance of the crawler float-type excavator chassis was evaluated after the skid support device was added. The chassis of the crawler float-type excavator was taken as the research object. A new model was also established for the driving resistance and tractive force of the chassis. Theoretical analysis was conducted on the extrusion force between the soil and the ground surface at the front of the skid. The sliding-cutting angle α and milter angle φ were determined to be the main structural parameters of the driving resistance. A skid scale model was constructed for the one-third of original size. The single-factor simulation was carried out using the driving speed and sinking depth in EDEM software. A systematic investigation was made on the influence of sliding-cutting angle α, milter angle φ, driving speed v and sinking depth on the forward resistance. The results showed that the forward resistance decreased with the increase of slip angle α, and milter angle φ, whereas, there was an increase with the increase of driving speed v, and sinking depth. The box-Behnken test was also carried out to explore the influence of slip-cutting angle, milter angle and forward speed on forward resistance. The influencing factors were taken as the sliding-cutting angle α, milter angle φ, and driving speed v, while the forward resistance was the response index. It was found that the driving speed v shared a very significant effect on the forward resistance (P＜0.01). The significant effect of sliding-cutting angle α, milter angle φ, and the square term v₂ of driving speed v on the advancing resistance (0.01＜P＜0.05). The optimal combination of parameters was obtained for the skid structure. Specifically, the least forward resistance was achieved, when the sliding-cutting angle α was 40°, the milter angle φ was 70° and the driving speed v was 0.1 m/s. Correspondingly, the forward resistances were 66.09 and 82.28 N in the simulation and soil bin test, respectively. The soil bin test showed that the skid driving speed and sinking depth had very significant effects on the skid forward resistance (P＜0.01). The skid driving speed and sinking depth were also proportional to the forward resistance, indicating the consistence with the simulation. The field test was carried out on the crawler float-type excavator before and after the skid support device. The resistance torque of the driving motor was reduced by 6.51%, which were 182.15 and 170.30 N·m, respectively. The sinking depth of the chassis was 178.1 and 164.5 mm, respectively, which were reduced by 7.64% than before. The performance of the excavator was outstandingly improved after adding the skid support device. This finding can provide a strong reference for the walking device of the ground machine system in paddy fields.