In order to improve the traction performance of a wheel of a micro-tiller on the soil surface of a paddy field, we extracted the surface curve of a cow's hoof and used the cow's hoof as a bionic prototype to design a bionic paddy wheel. In order to verify the passability of the bionic paddy wheel in paddy soil, a wheel-soil test bench was built in the experimental field with a moisture content of 36%. The test results show that under the condition of the same load on the wheel, the changing laws of torque, drawbar pull, and slip ratio of the bionic paddy wheel and the conventional vaned wheel are similar. The torque and drawbar pull of the bionic paddy wheel are higher than those of the conventional vaned wheel at the same slip ratio. The maximum torque and hook traction provided by the bionic paddy wheel and the conventional vaned wheel both increase with the increase of the load on the wheel. Under the same load on the wheel, the bionic paddy wheel is at least 22% higher than the conventional vaned wheel. Compared with the conventional vaned wheel, the bionic paddy wheel can provide a higher driving force and hook traction, which can improve the working efficiency of the vehicle in the paddy field.

Understanding the shear characteristics of paddy fields is of great significance for the design of high-trafficability paddy wheels and to improve the trafficability of the tiller in paddy fields. Taking the paddy soil in Poyang Lake area of Jiangxi Province as the research object, a simple, self-designed bevameter was constructed to measure the apparent cohesion c and apparent internal friction angle φ of paddy soil with water content of 37% by weight using an annular shear plate. The effects of different shear speeds, shear grouser heights, and shear plate diameters on the measured c and φ were investigated. The measured values of c and φ were 1.89–2.35 kPa and 10.2–11.4°(deg), respectively. With the increase in shear speed, shear plate diameter, and grouser height, the value of c increased. Shear plate diameter and shear speed had small effect on c, whose change rate did not exceed 7.8%. However, shear grouser height had a greater influence on c, and the measured c increased by 24.5%. The influence of the three factors on φ followed the order: shear speed > shear plate diameter > shear grouser height, but the variation in φ did not exceed 1.2°(deg). The optimal operational conditions were: shear plate diameter of 250 mm with inner diameter of 150 mm, shear grouser height of 10 mm, with a shear speed of π/120 rad/s, and the apparent cohesion and apparent internal friction angle are 1887.8 pa and 11.06° (deg), respectively.

In order to improve the traction performance of the micro-tiller wheel on the paddy soil surface, a bionic paddy wheel was designed with a cattle hoof as the bionic prototype, and its diameter and wheel width were 0.46 m and 0.08 m, respectively. The traction performance test was carried out in a soil bin test-bed with a moisture content of 36 %. The vertical loads were 82.57 N, 131.40 N and 179.42 N, respectively. The driving speeds were 0.3 m/s, 0.5 m/s and 0.7 m/s, respectively. The drawbar pull was in the range of 10 – 120 N. The results showed that at the driving speed of 0.7 m/s, with the increase of the vertical load, the driving torque and the drawbar pull are increasing. The vertical load has a significant effect on the change of driving torque and maximum drawbar pull. Under the vertical load of 179.42 N and different driving speeds, when the slip ratio is less than 0.37, the efficiency coefficient begins to grow rapidly, and the greater the driving speed is, the greater the growth rate is. When the slip ratio is about 0.37, the efficiency coefficient reaches the maximum and then begins to decrease. Driving speed has a significant effect on the maximum efficiency coefficient of wheels. This paper can provide a reference for the traction performance of the micro-tiller wheel on the paddy soil surface and the design of the new bionic paddy wheel.