Study On The Soil-Cutting Performance Of Multi-Claw Combination Of Mole Rats And Design Of Biomimetic Rotary Tillage Blade

Large tillage forces and high energy consumption of rotary cultivator are the urgent problems in agricultural tillage operations.Rotary tillage blades are the key component of rotary cultivator due to that the working performance of rotary tillage blades has a direct relationship with the working quality and power consumption of rotary cultivator.Therefore,it is necessary to optimize the geometric structures of the rotary tillage blade for reducing the power consumption of rotary cultivator.Bionic methods based on biological principles have been applied in engineering systems and modern technologies to improve or create new techniques.Mole rats are the special soil burrowing animals.When a mole rat digs soil,the five fore claws always work synergistically with an opened-up but co-plane configuration,which is described as multi-claw combination,for efficient cutting.Mole rats exert their greatest power to the soil following the rotation of humerus around its own long axis,and repeats this process.The principle of the claw-soil interaction is similar to that between the rotary tillage blade and soil.The characteristics of multi-claw combination can be used to design new tillage components for reducing drag and energy consumption.There were some literatures which had learned from the geometric characteristics of claws of mole rats to design bionic soil-rototilling and stubble-breaking blades.It optimized the geometric structure of blade edge,which could improve the soil penetration performance and straw crushing performance of balde.However,there are few studies on the soil cutting mechanism and the soil failure pattern of the multi-claw combination and rotary tillege blade.This paper aimed to study on the geometrical characteristics and the efficient soil cutting performance of multi-claw combination of mole rats,and then design bionic rotary tillage blades based on the characteristics of multi-claw combination trying to change the soil failure pattern for reducing the power requirement of tillage operations.Firstly,the geometrical characteristics and the efficient soil cutting performance of multi-claw combination of mole rats were studied.By measuring and analyzing the geometrical dimensions,it was found that multi-claw combination structure was a multi-narrow-tine combination structure,with adjustable spaces between adjacent tines,and then a mathematical model of multi-claw combination was established based on geometric elements.Moreover,the interaction between soil and multi-claw combination was simulated using the discrete element method?DEM?.Results showed that both the horizontal and vertical forces non-linearly increased with the rake angle rising.When the rake angle was 30?,there were the least horizontal and vertical forces and the best penetration performance of multi-claw combination.Interestingly,the parameter of soil failure-soil rupture distance ratio?m?of multi-claw combination was 19.6%lower than that of the conventional blade.Furthermore,the soil cutting mechanism and soil failure of multi-claw combination were deeply examined by the soil bin tests.Results showed that the multi-claw combination reduced the contact surface with the soil and developed the smallest soil failure wedge thus required less forces to cut soil.The average draught force of the multi-claw combination also increased non-linearly as the rake angle increased from10°to 90°,which was smaller than that of the conventional model.Thus,multi-claw combination played an important role in the soil-cutting performance and largely explained the high digging efficiency of mole rats.Then,the soil force model of multi-claw combination was developed using the laws of classical mechanics.And the force model was evaluated using the DEM and soil bin tests.It showed that the variation trend of calculated results with the rake angle was the same as that of the simulation results.On average,the calculated horizontal force was-30.73%smaller than the simulated value,but the calculated vertical force had a large difference with the simulated value.The soil bin tests results showed that both the calculated results and the test results increased non-linearly with the rake angle.The average error of the calculated horizontal force is-12.84%with respect to the test force within the range of±20%.Therefore,it was concluded that the force model could reasonably and accurately predict the soil resistance of multi-claw combination at different conditions,and the new soil failure pattern of the multi-claw combination was the overlap of multiple crescent failures which developed a small soil failure wedge for realizing the low soil forces result.The force model laid a theoretical foundation for the scientific research and practical application of multi-claw combination.Inspired by above analysis,we designed 9 biomimetic rotary tillage blades based on the geometric characteristics of multi-claw combination.By the 3-factor 3-level quadratic regression orthogonal test in an indoor soil bin,it was found the optimal combination of factors with the minimal torque?17.11 Nm?was ratio(n_cl)of 1.25 and the inclined angle???of 60?and rotary speed of 240 rpm.Then,the effects of the geometric characteristics of multi-claw combination on the torque of the optimal blade?BB-2?were studied by comparing with a conventional blade?CB?and a reported optimal biomimetic blade?BB-1?in the soil bin as the rotary speed increasing from 160 to 320 rpm.It was found that BB-1 and BB-2 averagely reduced the torque by 3.74%and 13.99%compared with CB,respectively.The torque of BB-2was largely reduced because multi-claw combination not only enhanced the penetrating and sliding cutting performance of the cutting edge,and also diminished the soil failure forces in the soil cutting process.Finally,the field experiment was conducted for further verifying the results of the soil bin tests,and it showed that the bionic rotary tillage balde significantly reduced the cultivation torque and power consumption,improved the soil breakage ratio,decreased the risk of the smearing of the furrow bottom,and realised the purpose of reducing drag and saving energy of rotary cultivator under the premise of ensuring the basic cultivation quality.