# Design and Test of Vertical Axis Rotating Cutters for Cutting Corn Roots and Crown
## 2 Materials and Methods  
### Materials  
#### 2.1.1 Preparation of Soil and Root-Crowns  
The test site was located in Harbin City, Heilongjiang Province (126\({}^{\circ}\)63\({}^{\prime}\) N, 45\({}^{\circ}\)75\({}^{\prime}\) E). Before the test, a ring cutter was employed to collect soil samples from a 0-10 cm depth. The samples were dried in an oven at 105 \({}^{\circ}\)C for 24 h. The average moisture content of the soil was measured to be 24.6% (wet-based), and the average bulk density of the soil was 1.36 g\(\cdot\)cm\({}^{-3}\) (wet-based) [20]. The ridge shape was measured using a ruler. The height and width of the ridge were 10 cm and 150 cm, respectively. The average spacing of the ridge was 65 cm. Subsequently, the conditions of corn root-crown in the field were sampled and measured. The average spacing of the root-crown was 26 cm, and the average height and diameter of the crown were 15 cm and 2.9 cm, respectively, as shown in Figure 1. To measure the distribution of underground roots, samples were taken from a 20 cm \(\times\) 20 cm soil layer. A brush was employed to clean the soil attached to the roots, and it was found that the roots were predominantly concentrated within a depth range of 0 to 12 cm and extended laterally up to 17 cm in width. Based on the method specified in GB/T6435-2014 \"Determination of Water and Other Active Substances in Feed\" [21], the moisture content of the roots and crown was determined, and their values were 15.6% \(\pm\) 0.8% and 23.23% \(\pm\) 0.6%, respectively. The JD2C-354 tractor ([PERSON], located in Moline, IL, USA) was employed as a power output device in the test. 2.1.2. Device Integrated by Bionic Cutters and Multi-Curve Cutters  
When the corn crown was cut by the ordinary curved cutter rotated vertically, the corn crown would slide along the edge of the cutter. It was difficult to make the corn crown enter the overlapping area composed of the moving cutter and the fixed cutter which would negatively affect the length of the corn crown after cutting. The cats could hook out the target and prevent the target from sliding through the special shape of their claws, so we were inspired by the special structure of the cat's claw to innovate the cutters for crushing corn crowns. The claw of a British Shorthair cat was selected as the bionic prototype. A microscope (OLYMPUS-SZX16, Olympus Corporation in Tokyo, Japan) was employed to obtain the image information of the cat's claw, and then the inner and outer contours of the claw were extracted using the function command in MATLAB software (2024a), as shown in Figure 2a. The equations of fitting the inner and outer contour curves were obtained, as shown in Equations (1) and (2). The fitting variance \(R^{2}\) for both equations was 0.997, proving that the fitting curves had high accuracy compared to the actual contours of the cat's claw. \[f(x_{1})=16\sin(0.41x_{1}-0.16)+14\sin(0.43x_{1}+2.46)\qquad\left(R^{2}=0.997\right) \tag{1}\]  
\[f(x_{2})=0.00164{x_{2}}^{3}-0.08856{x_{2}}^{2}+1.116x_{2}+0.3409\qquad\left(R ^{2}=0.997\right) \tag{2}\]  
where \(f(x_{1})\) and \(x_{1}\) are the control equation and abscissa of the inner contour of the cat's claw, respectively. \(f(x_{2})\) and \(x_{2}\) are the control equation and abscissa of the outer contour of the cat's claw, respectively. The moving cutter must have sufficient length to smoothly contact the crown. The radius of rotation for the moving cutter designed to cut the corn crown should be at least as large as the growth range of the crown in the context of corn ridge planting, where the width of the upper surface of the ridge is 150 mm. To ensure the stability of the moving cutter, the rotation radius should not be excessively large. Based on the agricultural machinery design manual, the rotation radius of the moving cutter for cutting crowns was designed to be 150 mm. Figure 1: Model of corn root–crown. Based on the distribution characteristics of corn roots in different soil layers, the cutter edges for different soil layers were designed, as shown in Figure 2b.